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Recommended SI units and conversion factors

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The following tables identify the preferred SI/metric units, along with conversion factors from customary units. Nomenclature for these tables

Space, time

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Length m naut mile km 1.852* E+00
mile km 1.609 344* E+00
chain m 2.011 68* E+01
link m 2.011 68* E−01
fathom m 1.828 8* E+00
m m 1.0* E+00
yd m 9.144* E−01
ft m 3.048* E−01
cm 3.048* E+01
in. mm 2.54* E+01
cm 2.54* E+00
cm mm 1.0* E+01
cm 1.0* E+00
mm mm 1.0 E+00
mil μm 2.54* E+01
micron (μ) μm 1.0* E+00
Length/length m/m ft/mi m/km 1.893 939 E−01
Length/volume m/m3 ft/U.S. gal m/m3 8.051 964 E+01
ft/ft3 m/m3 1.076 391 E+01
ft/bbl m/m3 1.917 134 E+00
Area m2 sq mile km2 2.589 988 E+00
section km2 2.589 988 E+00
ha 2.589 988 E+02
acre m2 4.046 856 E+03
ha 4.046 856 E−01
ha m2 1.0* E+04
sq yd m2 8.361 274 E−01
sq ft m2 9.290 304* E−02
cm2 9.290 304* E+02
sq in. mm2 6.451 6* E+02
cm2 6.451 6* E+00
cm2 mm2 1.0* E+02
cm2 1.0* E+00
mm2 mm2 1.0* E+00
Area/volume m2/m3 ft2 m2/cm3 5.699 291 E−03
Area/mass m2/kg cm m2/kg 1.0* E−01
m2/g 1.0* E−04
Volume, capacity m3 cubem km3 4.168 182 E+00[1]†
acre-ft m3 1.233 489 E+03
ha•m 1.233 489 E−01
m3 m3 1.0* E+00
cu yd m3 7.645 549 E−01
bbl (42 U.S. gal) m3 1.589 873 E−01
cu ft m3 2.831 685 E−02
dm3 L 2.831 685 E+01
U.K. gal m3 4.546 092 E−03
dm3 L 4.546 092 E+00
U.S. gal m3 3.785 412 E−03
dm3 L 3.785 412 E+00
liter dm3 L 1.0* E+00
U.K. qt dm3 L 1.136 523 E+00
U.S. qt dm3 L 9.463 529 E−01
U.S. pt dm3 L 4.731 765 E−01
Volume, capacity m3 U.K. fl oz cm3 2.841 308 E+01
U.S. fl oz cm3 2.957 353 E+01
cu in. cm3 1.638 706 E+01
mL cm3 1.0* E+00
Volume/length (linear displacement) m3/m bbl/in. m3/m 6.259 342 E+00
bbl/ft m3/m 5.216 119 E−01
ft3/ft m3/m 9.290 304* E−02
U.S. gal/ft m3/m 1.241 933 E−02
dm3/m L/m 1.241 933 E+01
Plane angle rad rad rad 1.0* E+00
deg (°) rad 1.745 329 E−02[2]
° 1.0* E+00
min (’) rad 2.908 882 E−04[2]
’ 1.0* E+00
sec (’’) rad 4.848 137 E−06[2]
’’ 1.0* E+00
Solid angle sr sr sr 1.0* E+00
Time s million years (MY) Ma 1.0* E+00[3]
yr a 1.0* E+00
wk d 7.0* E+00
d d 1.0* E+00
hr h 1.0* E+00
min 6.0* E+01
min s 6.0* E+01
h 1.666 667 E−02
min 1.0* E+00
s s 1.0* E+00
millimicrosecond ns 1.0* E+00

Mass, amount of substance

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Mass kg U.K. ton (long ton) Mg t 1.016 047 E+00
U.S. ton (short ton) Mg t 9.071 847 E−01
U.K. ton kg 5.080 235 E+01
U.S. cwt kg 4.535 924 E+01
kg kg 1.0* E+00
lbm kg 4.535 924 E−01
oz (troy) g 3.110 348 E+01
oz (av) g 2.834 952 E+01
g g 1.0* E+00
grain mg 6.479 891 E+01
mg mg 1.0* E+00
g g 1.0* E+00
Amount of substance mol lbm mol kmol 4.535 924 E−01
g mol kmol 1.0* E−03
std m3 (0°C, 1 atm) kmol 4.461 58 E−02[4][5]
std m3 (15°C, 1 atm) kmol 4.229 32 E−02[4][5]
std ft3 (60°F, 1 atm) kmol 1.195 3 E−03[4][5]

Calorific value, heat, entropy, heat capacity

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Calorific value (mass basis) J/kg Btu/lbm MJ/kg 2.326 E−03
kJ/kg J/g 2.326 E+00
(kW•h)/kg 6.461 112 E−04
cal/g kJ/kg J/g 4.184* E+00
cal/lbm J/kg 9.224 141 E+00
Calorific value (mole basis) J/mol kcal/g mol kJ/kmol 4.184* C+03[5]
Btu/lbm mol MJ/kmol 2.326 E−03[5]
kJ/kmol 2.326 E+00[5]
Calorific value(volume basis–solids and liquids) J/m3 therm/U.K. gal MJ/m3 kJ/dm3 2.320 80 E+04
kJ/m3 2.320 80 E+07
(kW•h)/dm3 6.446 660 E+00
Btu/U.S. gal MJ/m3 kJ/dm3 2.787 163 E−01
kJ/m3 2.787 163 E+02
(kW•h)/m3 7.742 119 E−02
Btu/U.K. gal MJ/m3 kJ/dm3 2.320 8 E−01
kJ/m3 2.320 8 E+02
(kW•h)/m3 6.446 660 E−02
Btu/ft3 MJ/m3 kJ/dm3 3.725 895 E−02
kJ/m3 3.725 895 E+01
(kW•h)/m3 1.034 971 E−02
kcal/m3 MJ/m3 kJ/dm3 4.184* E−03
kJ/m3 4.184* E−03
cal/mL MJ/m3 4.184* E+00
ft-lbf/U.S. gal kJ/m3 3.581 692 E−01
Calorific value (volume basis–gases) J/m3 cal/mL kJ/m3 J/dm3 4.184* E+03
kcal/m3 kJ/m3 J/dm3 4.184* E+00
Btu/ft3 kJ/m3 J/dm3 3.725 895 E+01
(kW•h)/m3 1.034 971 E−02
Specific entropy J/kg•K Btu/(lbm-°R) kJ(kg•K) J(g•K) 4.186 8* E+00
cal/(g-°K) kJ(kg•K) J(g•K) 4.184* E+00
kcal/(kg-°C) kJ(kg•K) J(g•K) 4.184* E+00
Specific heat J/kg•K kW-hr/(kg-°C) kJ(kg•K) J(g•K) 3.6* E+03
capacity (mass basis) Btu/(lbm-°F) kJ(kg•K) J(g•K) 4.186 8* E+00
kcal(kg-°C) kJ(kg•K) J(g•K) 4.184* E+00
Molar heat J/mol•K Btu/(lbm mol-°F) kJ(kmol•K) 4.186 8* E+00[5]
capacity cal/(g mol-°C) kJ(kmol•K) 4.184* E−00[5]

Temperature, pressure, vacuum

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Temperature (absolute) K °R K 5/9
°K K 1.0* E+00
Temperature (traditional) K °F °C (F−32)/1.8
°C °C 1.0* E+00
Temperature (difference) K °F K °C 5/9 E+00
°C K °C 1.0* E+00
Temperature/length (geothermal gradient) K/m °F/100 ft mK/m 1.822 689 E+01
Length/temperature (geothermal step) m/K ft°F m/K 5.486 4* E−01
Pressure Pa atm (760 mm Hg at 0°C or 14.696 (lbf/in.2) MPa 1.013 25* E−01
kPa 1.013 25* E+02
bar 1.013 25* E+00
bar MPa 1.0* E−01
kPa 1.0* E+02
bar 1.0* E+00
at (technical atm, kbf/cm2) MPa 9.806 65* E−02
kPa 9.806 65* E+01
bar 9.806 65* E−01
Pressure Pa lbf/in.2 (psi) MPa 6.894 757 E−03
kPa 6.894 757 E+00
bar 6.894 757 E−02
in. Hg (32°F) kPa 3.386 38 E+00
in. Hg (60°F) kPa 3.376 85 E+00
in. H2O (39.2°F) kPa 2.490 82 E−01
in. H2O (60°F) kPa 2.488 4 E−01
Mm Hg (0°C)=torr kPa 1.333 224 E−01
Cm H2O (4°C) kPa 9.806 38 E−02
lbf/ft2 (psf) kPa 4.788 026 E−02
µm Hg (0°C) Pa 1.333 224 E−01
µbar Pa 1.0* E−01
dyne/cm2 Pa 1.0* E−01
Vacuum, draft Pa in. Hg (60°F) kPa 3.376 85 E+00
in. H2O (39.2°F) kPa 2.490 82 E−01
Mm Hg (0°C)=torr kPa 1.333 224 E−01
Cm H2O (4°C) kPa 9.806 38 E−02
Liquid heat m ft m 3.048* E−01
in. mm 2.54* E+01
cm 2.54* E+00
Pressure drop/length Pa/m psi/ft kPa/m 2.262 059 E+01
psi/100 ft kPa/m 2.262 059 E−01

Density, specific volume, concentration, dosage

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Density (gases) kg/m3 lbm/ft3 kg/m3 1.601 846 E+01
g/m3 1.601 846 E+04
Density (liquids) kg/m3 lbm/U.S. gal kg/m3 1.198 264 E+02
g/cm3 1.198 264 E−01
lbm/U.K. gal kg/m3 9.997 633 E+01
kg/dm3 9.977 633 E−02
lbm/ft3 kg/m3 1.601 846 E+01
g/cm3 1.601 846 E−02
g/cm3 kg/m3 1.0* E+03
kg/dm3 1.0* E+00
°API g/cm3 141.5/(131.5+°API)
Density (solids) kg/m3 lbm/ft3 kg/m3 1.601 846 E+01
Specific volume(gases) m3/kg ft3/lbm m3/kg 6.242 796 E−02
m3/g 6.242 796 E−05
Specific volume (liquids) m3/kg ft3/lbm dm3/kg 6.242 796 E+01
U.K. gal/lbm dm3/kg cm3/g 1.002 242 E+01
U.S. gal/lbm dm3/kg cm3/g 8.345 404 E+00
Specific volume (mole basis) ft3/mol L/g mol m3/kmol 1.0* E+00[5]
ft3/lbm mol m3/kmol 6.242 796 E−02[5]
Specific volume (clay yield) m3/kg bbl/U.S. ton m3/t 1.752 535 E−01
bbl/U.K. ton m3/t 1.564 763 E−01
Yield (shale distillation) m3/kg bbl/U.S. ton dm3/t L/t 1.752 535 E+02
bbl/U.K. ton dm3/t L/t 1.564 763 E+02
U.S. gal/U.S. ton dm3/t L/t 4.172 702 E+00
U.S. gal/U.K. ton dm3/t L/t 3.725 627 E+00
Concentration(mass/mass) kg/kg wt% kg/kg 1.0* E−02
g/kg 1.0* E+01
wt ppm mg/kg 1.0* E+00
Concentration(mass/volume) kg/m3 lbm/bbl kg/m3 g/dm3 2.853 010 E+00
g/U.S. gal kg/m3 2.641 720 E−01
g/U.K. gal kg/m3 g/L 2.199 692 E−01
Concentration(mass volume) kg/m3 lbm/1,000 U.S. gal g/m3 mg/dm3 1.198 264 E+02
lbm/1,000 U.K. gal g/m3 mg/dm3 9.977 633 E+01
grains/U.S. gal g/m3 mg/dm3 1.711 806 E+01
grains/ft3 mg/m3 2.288 352 E+03
lbm/1,000 bbl g/m3 mg/dm3 2.853 010 E+00
mg/U.S. gal g/m3 mg/dm3 2.641 720 E−01
grains/100 ft3 mg/m3 2.288 352 E+01
Concentration(volume/volume) m3/ m3 bbl/bbl m3/m3 1.0* E+00
ft3/ft3 m3/m3 1.0* E+00
bbl/acre-ft m3/m3 1.288 923 E−04
m3/ha•m 1.288 923 E+00
vol % m3/m3 1.0* E−02
U.K. gal/ft3 dm3/m3 L/m3 1.605 437 E+02
U.S. gal/ft3 dm3/m3 L/m3 1.336 806 E+02
mL/U.S. gal dm3/m3 L/m3 2.641 720 E−01
mL/U.K. gal dm3/m3 L/m3 2.199 692 E−01
vol ppm cm3/m3 1.0* E+00
dm3/m3 L/m3 1.0* E−03
U.K. gal/1,000 bbl cm3/m3 1.859 406 E+01
U.S. gal/1,000 bbl cm3/m3 2.380 952 E+01
U.K. pt/1,000 bbl cm3/m3 3.574 253 E+00
Concentration mol/m3 lbm mol/U.S. gal kmol/m3 1.198 264 E+02
lbm mol/U.K. gal kmol/m3 9.977 633 E+01
lbm mol/ft3 kmol/m 1.601 846 E+01
std ft3 (60°F,1 atm)/bbl kmol/m3 7.518 18 E−03
Concentration(volume/mole) m3/mol U.S. gal/1,000 std ft3 (60°F/60°F) dm3/kmol L/kmol 3.166 93 E+00
bbl/million std ft3 (60°F/60°F) dm3/kmol L/kmol 1.330 11 E−01

Facility throughput, capacity

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Throughput (mass basis) kg/s million lbm/yr t/a Mg/a 4.535 924 E+02
U.K. ton/yr t/a Mg/a 1.016 047 E+00
U.S. ton/yr t/a Mg/a 9.071 847 E−01
U.K. ton/D t/d Mg/d 1.016 047 E+00
t/h, Mg/h 4.233 529 E−02
U.S. ton/D t/d 9.071 847 E−01
t/h, Mg/h 3.779 936 E−02
U.K. ton/hr t/h Mg/h 1.016 047 E+00
U.S. ton/hr t/h Mg/h 9.071 847 E−01
lbm/hr kg/h 4.535 924 E−01
Throughput (volume basis) m3/s bbl/D t/a 5.803 036 E+01[6]
m3/d 1.589 873 E−01
m3/h 6.624 471 E−03
ft3/D m3/d 2.831 685 E−02
bbl/hr m3/h 1.589 873 E−01
ft3/h m3/h 2.831 685 E−02
U.K. gal/hr m3/h 4.546 092 E−03
L/s 1.262 803 E−03
U.S. gal/hr m3/h 3.785 412 E−03
L/s 1.051 503 E−03
U.K. gal/min m3/h 2.727 655 E−01
L/s 7.576 819 E−02
U.S. gal/min m3/h 2.271 247 E−01
L/s 6.309 020 E−02
Throughput (mole basis) mol/s lbm mol/hr kmol/h 4.535 924 E−01
kmol/s 1.259 979 E−04[7]
Pipeline capacity m3/m bbl/mile m3/km 9.879 013 E−02
Flow rate (mass basis) kg/s U.K. ton/min kg/s 1.693 412 E+01
U.S. ton/min kg/s 1.511 974 E+01
U.K. ton/hr kg/s 2.822 353 E−01
U.S. ton/hr kg/s 2.519 958 E−01
U.K. ton/D kg/s 1.175 980 E−02
U.S. ton/D kg/s 1.049 982 E−02
million lbm/yr kg/s 5.249 912 E+02
U.K. ton/yr kg/s 3.221 864 E−05
U.S. ton/yr kg/s 2.876 664 E−05
lbm/s kg/s 4.535 924 E−01
lbm/min kg/s 7.559 873 E−03
lbm/hr kg/s 1.259 979 E−04
Flow rate (volume basis) m3/s bbl/D m3/d 1.589 873 E−01
L/s 1.840 131 E−03
ft3/D m3/d 2.831 685 E−02
L/s 3.277 413 E−04
bbl/hr m3/s 4.416 314 E−05
L/s 4.416 314 E−02
ft3/hr m3/s 7.865 791 E−06
L/s 7.865 791 E−03
U.K. gal/hr dm3/s L/s 1.262 803 E−03
U.S. gal/hr dm3/s L/s 1.051 503 E−03
U.K. gal/min dm3/s L/s 7.576 820 E−02
U.S. gal/min dm3/s L/s 6.309 020 E−02
ft3/min dm3/s L/s 4.719 474 E−01
ft3/s dm3/s L/s 2.831 685 E+01
Flow rate (mole basis) mol/s lbm mol/s kmol/s 4.535 924 E−0113
lbm mol/hr kmol/s 1.259 979 E−0413
million scf/D kmol/s 1.383 449 E−0213
Flow rate/length (mass basis) kg/s•m lbm/(s-ft) kg/(s•m) 1.488 164 E+00
lbm/(hr-ft) kg/(s•m) 4.133 789 E−04
Flow rate/length m2/s U.K. gal/(min-ft) m2/s m3/(s•m) 2.485 833 E−04
U.S. gal/(min-ft) m2/s m3/(s•m) 2.069 888 E−04
U.K. gal/(hr-in.) m2/s m3/(s•m) 4.971 667 E−05
U.S. gal/(hr-in.) m2/s m3/(s•m) 4.139 776 E−05
U.K. gal/(hr-ft) m2/s m3/(s•m) 4.143 055 E−06
U.S. gal/(hr-ft) m2/s m3/(s•m) 3.449 814 E−06
Flow rate/area (mass basis) kg/s•m2 lbm/(s-ft2) kg/s•m2 4.882 428 E+00
lbm/(hr-ft2) kg/s•m2 1.356 230 E−03

Flow rate

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Flow rate/area m/s ft3/(s-ft2) m/s m3/(s•m2) 3.048* E−01
ft3/(min-ft2) m/s m3/(s•m2) 5.08* E−03
U.K. gal/(hr-in.2) m/s m3/(s•m2) 1.957 349 E−03
U.S. gal/(hr-in.2) m/s m3/(s•m2) 1.629 833 E−03
U.K. gal/(min-ft2) m/s m3/(s•m2) 8.155 621 E−04
U.S. gal/(min-ft2) m/s m3/(s•m2) 6.790 972 E−04
U.K. gal/(hr-ft2) m/s m3/(s•m2) 1.359 270 E−05
U.S. gal/(hr-ft2) m/s m3/(s•m2) 1.131 829 E−05
Flow rate/pressure drop (productivity index) m3/s•Pa bbl/(D-psi) m3/(d•kPa) 2.305 916 E−02

Energy, work, power

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Energy, work J quad MJ 1.055 056 E+12
TJ 1.055 056 E+06
EJ 1.055 056 E+00
MW•h 2.930 711 E+08
GW•h 2.930 711 E+05
TW•h 2.930 711 E+02
therm MJ 1.055 056 E+02
kJ 1.055 056 E+05
kW•h 2.930 711 E+01
U.S. tonf-mile MJ 1.431 744 E+01
hp-hr MJ 2.684 520 E+00
kJ 2.684 520 E+03
kW•h 7.456 999 E−01
ch-hr or CV-hr MJ 2.647 796 E+00
Kj 2.647 796 E+03
kW•h 7.354 99 E−01
kW-hr MJ 3.6* E+00
kJ 3.6* E+03
Chu kJ 1.899 101 E+00
kW•h 5.275 280 E−04
Btu kJ 1.055 056 E+00
kW•h 2.930 711 E−04
kcal kJ 4.184* E+00
cal kJ 4.184* E−03
ft-lbf kJ 1.344 818 E−03
lbf-ft kJ 1.355 818 E−03
J kJ 1.0* E−03
lbf-ft2/s2 kJ 4.214 011 E−05
erg J 1.0* E−07
Impact energy J kgf•m J 9.806 650* E+00
lbf-ft J 1.355 818 E+00
Work/length J/m U.S. tonf-mile/ft MJ/m 4.697 322 E+01
Surface energy J/m2 erg/cm2 mJ/m2 1.0* E+00
Specific impact J/m2 kgf•m/cm2 J/cm2 9.806 650* E−00
energy Power lbf•ft/in.2 J/cm2 2.101 522 E−01
W quad/yr MJ/a 1.055 056 E+12
TJ/a 1.055 056 E+06
EJ/a 1.055 056 E+00
erg/a TW 3.170 979 E−27
GW 3.170 979 E−24
million Btu/hr MW 2.930 711 E−01
ton of refrigeration kW 3.516 853 E+00
Btu/s kW 1.055 056 E+00
kW kW 1.0* E+00
hydraulic horsepower—hhp kW 7.460 43 E−01
hp (electric) kW 7.46* E−01
hp (550 ft-lbf/s) kW 7.456 999 E−01
ch or CV kW 7.354 99 E−01
Btu/min kW 1.758 427 E−02
ft•lbf/s kW 1.355 818 E−03
kcal/hr W 1.162 222 E+00
Btu/hr W 2.930 711 E−01
ft•lbf/min W 2.259 697 E−02
Power/area W/m2 Btu/s•ft2 kW/m2 1.135 653 E+01
cal/hr•cm2 kW/m2 1.162 222 E−02
Btu/hr•ft2 kW/m2 3.154 591 E−03
Heat flow unit—hfu µcal/s•cm2 mW/m2 4.184* E+01
(geothermics)
Heat release rate, W/m2 hp/ft3 kW/m3 2.633 414 E+01
mixing power cal/(hr•cm3) kW/m3 1.162 222 E+00
Btu/(s•ft3) kW/m3 3.725 895 E+01
Btu/(hr•ft3) kW/m3 1.034 971 E−02
Heat generation unit—hgu (radioactive rocks) cal/(s•cm3) µW/m3 4.184* E+12
Cooling duty (machinery) W/W Btu/(bhp-hr) W/kW 3.930 148 E−01
Specific fuel consumption (mass basis) kg/J lbm/(hp-hr) mg/J kg/MJ 1.689 659 E−01
kg/(kW•h) 6.082 774 E−01
Specific fuel consumption (volume basis) m3/J m3/(kW-hr) dm3/MJ mm3/J 2.777 778 E+02
dm3/(kW•h) 1.0* E+03
U.S. gal/(hp-hr) dm3/MJ mm3/J 1.410 089 E+00
dm3(kW•h) 5.076 321 E+00
U.K. pt/(hp-hr) dm3/MJ mm3/J 2.116 809 E−01
dm3/(kW•h) 7.620 512 E−01
Fuel consumption (automotive) m3/m U.K. gal/mile dm3/100 km L/100 km 2.824 811 E+02
U.S. gal/mile dm3/100 km L/100 km 2.352 146 E+02
mile/U.S. gal km/dm3 km/L 4.251 437 E−01
mile/U.K. gal km/dm3 km/L 3.540 060 E−01

Mechanics

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Velocity (linear), m/s knot km/h 1.852* E+00
speed mile/hr km/h 1.609 344* E+00
m/s m/s 1.0* E+00
ft/s m/s 3.048* E−01
cm/s 3.048* E+01
m/ms 3.048* E−04[8]
ft/min m/s 5.08* E−03
cm/s 5.08* E−01
ft/hr mm/s 8.466 667 E−02
cm/s 8.466 667 E−03
ft/D mm/s 3.527 778 E−03
m/d 3.048* E−01
in. mm/s 2.54* E+01
cm/s 2.54* E+00
in./min mm/s 4.233 333 E−01
cm/s 4.233 333 E−02
Velocity (angular) rad/s rev/min rad/s 1.047 198 E−01
rev/s rad/s 6.283 185 E+00
degree/min rad/s 2.908 882 E−04
Interval transit time s/m s/ft s/m µs/m 3.280 840 E+00[9]
Corrosion rate m/s in./yr (ipy) mm/a 2.54* E+01
mil/yr mm/a 2.54* E−02
Rotational frequency rev/s rev/s rev/s 1.0* E+00
rev/min rev/s 1.666 667 E−02
rev/min rad/s 1.047 198 E−01
Acceleration (linear) m/s2 ft/s2 m/s2 3.048* E−01
cm/s2 3.048* E+01
gal(cm/s2) m/s2 1.0* E−02
Acceleration(rotational) rad/s2 rad/s2 rad/s2 1.0* E+00
rpm/s rad/s2 1.047 198 E−01
Momentum kg•m/s lbm•ft/s kg•m/s 1.382 550 E−01
Force N U.K. tonf kN 9.964 016 E+00
U.S. tonf kN 8.896 443 E+00
kgf (kp) N 9.806 650* E+00
lbf N 4.448 222 E+00
N N 1.0* E+00
pdl mN 1.382 550 E+02
dyne mN 1.0* E−02
Bending moment, N•m U.S. tonf-ft kN•m 2.711 636 E+00[10])
torque kgf-m N•m 9.806 650* E+00[10]
lbf-ft N•m 1.355 818 E+00[10]
lbf-in. N•m 1.129 848 E−01[10]
pdl-ft N•m 4.214 011 E−02[10]
Bending moment/ N•m/m (lbf-ft)/in. (N•m)/m 5.337 856 E+01[10]
length (kgf-m)/m (N•m)/m 9.806 650* E+00[10]
(lbf-in.)/in. (N•m)/m 4.448 222 E+00[10]
Elastic modul (Young’s, shear bulk) Pa lbf/in.2 GPa 6.894 757 E−06
Moment of inertia kg•m2 lbm-ft2 kg•m2 4.214 011 E−02
Moment of section m4 in.4 cm4 4.162 314 E+01
Section modulus m3 cu in. cm3 1.638 706 E+01
cu ft cm3 1.638 706 E+04
mm3 2.831 685 E+04
m3 2.831 685 E−02
Stress Pa U.S. tonf/in.2 MPa N/mm2 1.378 951 E+01
kgf/mm2 MPa N/mm2 9.806 650* E+00
U.S. tonf/ft2 MPa N/mm2 9.576 052 E−02
lbf/in.2 (psi) MPa N/mm2 6.894 757 E−03
lbf/ft2 (psf) kPa 4.788 026 E−02
dyne/cm2 Pa 1.0* E−01
Yield point, gel strength (drilling fluid) lbf/100 ft2 Pa 4.788 026 E−01
Mass/length kg/m lbm/ft kg/m 1.488 164 E+00
Mass/area kg/m2 U.S. ton/ft2 Mg/m2 9.764 855 E+00
structural loading, bearing capacity (mass basis) lbm/ft2 kg/m2 4.882 428 E+00
Coefficient of thermal expansion m/(m•K) in./(in.-°F) mm/(mm•K) 5.555 556 E−01

Transport properties

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Diffusivity m2/s ft2/s mm2/s 9.290 304* E+04
cm2/s mm2/s 1.0* E+02
ft2/hr mm2/s 2.580 64* E+01
Thermal resistance (k•m2)/W (°C-m2•hr)/kcal (K•m2)kW 8.604 208 E+02
(°F-ft2 hr)/Btu (K•m2)kW 1.761 102 E+02
Heat flux W/m2 Btu/(hr-ft2) kW/m2 3.154 591 E−03
Thermal conductivity W/(m•K) (cal/s-cm2-°C/cm W/(m•K) 4.184* E+02
Btu/(hr-ft2-°F/ft) W/(m•K) 1.730 735 E+00
kJ•m/(h•m2K) 6.230 646 E+00
kcal/(hr-m2-°C/m) W/(m•K) 1.162 222 E+00
Btu/(hr-ft2-°F/in.) W/(m•K) 1.442 279 E−01
cal/(hr-cm2-°C/cm) W/(m•K) 1.162 222 E−01
Heat transfer coefficient W/(m2•K) cal/(s-cm2-°C) kW/(m2•K) 4.184* E+01
Btu/(s-ft2-°F) kW/(m2•K) 2.044 175 E+01
cal/(hr-cm2-°C) kW/(m2•K) 1.162 222 E−02
Btu/(hr-ft2-°F) kW/(m2•K) 5.678 263 E−03
kJ(h•m2•K) 2.044 175 E+01
Btu/(hr-ft2-°R) kW/(m2•K) 5.678 263 E−03
kcal/(hr-m2-°C) kW/(m2•K) 1.162 222 E−03
Volumetric heat kW/(m3•K) Btu/(s-ft3-°F) kW/(m3•K) 6.706 611 E+01
transfer coefficient Btu/(hr-ft3-°F) kW/(m3•K) 1.862 947 E−02
Surface tension N/m dyne/cm mN/m 1.0* E+00
Viscosity (dynamic) Pa•s (lbf-s)/in.2 Pa•s (N•s)/m2 6.894 757 E+03
(lbf-s)/ft2 Pa•s (N•s)/m2 4.788 026 E+01
(kgf-s)/m2 Pa•s (N•s)/m2 9.806 650* E+00
lbm/(ft-s) Pa•s (N•s)/m2 1.488 164 E+00
(dyne-s)/cm2 Pa•s (N•s)/m2 1.0* E−01
cp Pa•s (N•s)/m2 1.0* E−03
lbm/(ft-hr) Pa•s (N•s)/m2 4.133 789 E−04
Viscosity (kinematic) m2/s ft2/s mm2/s 9.290 304* E+04
in.2/s mm2/s 6.451 6* E+02
m2/hr mm2/s 2.777 778 E+02
cm2/s mm2/s 1.0* E+02
ft2/hr mm2/s 2.580 64* E+01
cSt mm2/s 1.0* E+00
Permeability m2 darcy μm2 9.869 233 E−01[11]
millidarcy μm2 9.869 233 E−04[11]
10−3μm2 9.869 233 E−01[11]

Electricity, magnetism

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Admittance S S S 1.0* E+00
Capacitance F μF μF 1.0* E+00
Capacity, storage battery C A•hr kC 3.6* E+00
Charge density C/m3 C/mm3 C/mm3 1.0* E+00
Conductance S S S 1.0* E+00
Ω(mho) S 1.0* E+00
Conductivity S/m S/m S/m 1.0* E+00
Ω/m S/m 1.0* E+00
m Ω/m mS/m 1.0* E+00
Current density A/m2 A/mm2 A/mm2 1.0* E+00
Displacement C/m2 C/cm2 C/cm2 1.0 E+00
Electric charge C C C 1.0* E+00
Electric current A A A 1.0* E+00
Electric dipole moment C•m C•m C•m 1.0* E+00
Electric field strength V/m V/m V/m 1.0* E+00
Electric flux C C C 1.0* E+00
Electric polarization C/m2 C/m2 C/m2 1.0* E+00
Electric potential V V V 1.0* E+00
mV mV 1.0* E+00
Electromagnetic moment A•m2 A•m2 A•m2 1.0* E+00
Electromotive force V V V 1.0* E+00
Flux of displacement C C C 1.0* E+00
Frequency Hz cycles/s Hz 1.0* E+00
Impedance Ω Ω Ω 1.0* E+00
Interval transit time s/m μs/ft μs/m 3.280 840 E+00
Linear current density A/m A/mm A/mm 1.0* E+00
Magnetic dipole moment Wb•m Wb•m Wb•m 1.0* E+00
Magnetic field strength A/m A/mm A/mm 1.0* E+00
oersted A/m 7.957 747 E+01
gamma A/m 7.957 747 E−04
Magnetic flux Wb mWb mWb 1.0* E+00
Magnetic flux density T mT mT 1.0* E+00
gauss T 1.0* E−04
Magnetic induction T mT mT 1.0* E+00
Magnetic moment A•m2 A•m2 A•m2 1.0* E+00
Magnetic polarization T mT mT 1.0* E+00
Magnetic potential difference A A A 1.0* E+00
Magnetic vector potential Wb/m Wb/m Wb/m 1
Magnetization A/m A/mm A/mm 1
Modulus of admittance S S S 1
Modulus of impedance Ω Ω Ω 1
Mutual inductance H H H 1
Permeability H/m µH/m µH/m 1
Permeance H H H 1
Permittivity F/m µF/m µF/m 1
Potential difference V V V 1
Quantity of electricity C C C 1
Reactance Ω Ω Ω 1
Reluctance H–1 H–1 H–1 1
Resistance Ω Ω Ω 1
Resistivity Ω•m Ω•cm Ω•cm 1
Ω•m Ω•m 1 [12]
Self inductance H mH mH 1
Surface density of charge C/m2 mC/m2 mC/m2 1
Susceptance S S S 1
Volume density of charge C/m3 C/mm3 C/mm3 1

Acoustic, light, radiation

Quantity SI Unit Customary Unit Metric Unit SPE Preferred Metric Unit Other Allowable Conversion Factor:*Multiply Customary Unit by Factor To Get Metric Unit
Absorbed dose Gy rad Gy 1.0* E−02
Acoustical energy J J J 1
Acoustical intensity W/m2 W/cm2 W/m2 1.0* E+04
Acoustical power W W W 1
Sound pressure N/m2 N/m2 N/m2 1
Illuminance lx footcandle lx 1.076 391 E+01
Illumination lx footcandle lx 1.076 391 E+01
Irradiance W/m2 W/m2 W/m2 1
Light exposure lx•s footcandle•s lx•s 1.076 391 E+01
Luminance cd/m2 cd/m2 cd/m2 1
Luminous efficacy lm/W lm/W lm/W 1
Luminous exitance lm/m2 lm/m2 lm/m2 1
Luminous flux lm lm lm 1
Luminous intensity cd cd cd 1
Quantity of light ℓm•s talbot ℓm•s 1.0* E+00
Radiance W/(m2•sr) W/(m2•sr) W/(m2•sr) 1
Radiant energy J J J 1
Radiant flux W W W 1
Radiant intensity W/sr W/sr W/sr 1
Radiant power W W W 1
Wavelength m Å nm 1.0* E−01
Capture unit m−1 10−3cm−1 m−1 1.0* E+01
10−3cm−1 1
m−1 m−1 1
Radioactivity curie Bq 3.7* E+10
Capillary Pa ft (fluid) m (fluid) 3.048* E−01
Compressibility of Pa−1 psi−1 Pa−1 1.450 377 E−04
reservoir fluid kPa−1 1.450 377 E−01
Corrosion allowance m in. mm 2.54* E+01
Corrosion rate m/s mil/yr mm/a 2.54* E−02
(mpy)
Differential orifice Pa in. H2O kPa 2.488 4 E−01
pressure (at 60°F) cm H2O 2.54* E+00
Gas-oil ratio m3/m3 scf/bbl "standard" 1.801 175 E−01[1]
m3/m3
Gas rate m3/s scf/D "standard" 2.863 640 E−02[1]
m3/d
Geologic time s yr Ma
Heat (fluid mechanics) m ft m 3.048* E−01
cm 3.048* E+01
Heat exchange rate W Btu/hr kW 2.930 711 E−04
kJ/h 1.055 056 E+00
Mobility m2/Pa•s d/cp µm2/mPa•s 9.869 233 E−01
µm2/Pa•s 9.869 233 E+02
Net pay thickness m ft m 3.048* E−01
Oil rate m3/s bbl/D m3/d 1.589 873 E−01
short ton/yr mg/a ta 9.071 847 E−01
Particle size m micron µm 1.0*
Permeability-thickness m3 md-ft md•m µm2•m 3.008 142 E−04
Pipe diameter (actual) m in. cm 2.54* E+00
mm 2.54* E+01
Pressure buildup Pa psi kPa 6.894 757 E+00[2]
per cycle
Productivity index m3/Pa•s bbl/(psi-D) m3(kPa•d) 2.305 916 E−02[2]
Pumping rate m3/s U.S. gal/min m3/h 2.271 247 E−01
L/s 6.309 020 E−02
Revolutions per minute rad/s rpm rad/s 1.047 198 E−01
rad/m 6.283 185 E+00
Recovery/unit volume m3/m3 bbl/(acre-ft) m3/m3 1.288 931 E−04
(oil) m3/ha•m 1.288 931 E+00
Reservoir area m2 sq mile km2 2.589 988 E+00
acre ha 4.046 856 E−01
Reservoir volume m3 acre-ft m3 1.233 482 E+03
ha•m 1.233 482 E−01
Specific productivity m3/Pa•s•m bbl/(D-psi-ft) m3/(kPa•d•s) 7.565 341 E−02[2]
index
Surface or interfacial tension in reservoir capillaries N/m dyne/cm mN/m 1.0* E+00
Torque N•m lbf-ft N•m 1.355 818 E+00[3]
Velocity (fluid flow) m/s ft/s m/s 3.048* E−01
Vessel diameter m
1–100 cm in. cm 2.54* E+00
above 100 cm ft m 3.048* E−01

*An asterisk indicates the conversion factor is exact using the numbers shown; all subsequent numbers are zeros.

References

  1. ↑ 1.0 1.1 1.2 Since 1893, the U.S. basis of length measurement has been derived from metric standards. In 1959, a small refinement was made in the definition of the yard to resolve discrepancies both in this country and abroad, which changed its length from 3600/3937 m to 0.9144 m exactly. This resulted in the new value being shorter by two parts in a million. At the same time, it was decided that any data in feet derived from and published as a result of geodetic surveys within the U.S. would remain with the old standard (1 ft=1200/3937 m) until further decision. This foot is named the U.S. survey foot. As a result, all U.S. land measurements in U.S. customary units will relate to the meter by the old standard. All the conversion factors in these tables for units referenced to this footnote are based on the U.S. survey foot, rather than the international foot. Conversion factors for the land measure given below may be determined from the following relationships:
    1 league=3 miles (exactly)
    1 rod=16½ ft (exactly)
    1 chain=66 ft (exactly)
    1 section=1 sq mile
    1 township=36 sq miles
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 This value was adopted in 1956. Some of the older International Tables use the value 1.055 04 E+03. The exact conversion factor is 1.055 055 852 62* E+03
  3. ↑ 3.0 3.1 This sometimes is called the moment of inertia of a plane section about a specified axis.
  4. ↑ 4.0 4.1 4.2 The exact conversion factor is 1.638 706 4*E−05.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Defined (not measured) value. (This reference should be ref 13)
  6. ↑ Not the same dimensions as “millidarcy-foot.”
  7. ↑ Not the same as reservoir “perm.”
  8. ↑ The exact conversion factor is 4.535 923 7*E−01.
  9. ↑ The exact conversion factor is 4.448 615 260 5*E+00.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 10.7 Torque unit; see text discussion of “Torque and Bending Moment.”
  11. ↑ 11.0 11.1 11.2 Torque divided by length; see text discussion of “Torque and Bending Moment.”
  12. ↑ Defined (not measured) value.

See also

SI metric conversion factors

Nomenclature for SI metric conversion tables

Symbols in alphabetical order

Category

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