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Unit Equivalents
Metric to American
American to Metric
Metric to Metric
American to American
Area:
1 mm
2
=0.00155 in.
2
=0.00001076 ft
2
1 in.
2
=645.2 mm
2
=6.452 cm
2
1 cm
2
=0.155 in.
2
=0.001076 ft
2
=0.0006452 m
2
1 m
2
=1550 in.
2
=10.76 ft
2
1 ft
2
=92903 mm
2
=929.03 cm
2
=0.0929 m
2
1 acre=43560 ft
2
1 circular mil=0.7854 square mil
=5.067 x 10
-10
m
2
=7.854 x 10
-5
in.
2
Density and Specific Gravity:
1 g/cm
3
=0.036 13 lb/in.
3
=62.43 lb/ft
3
1 lb/in.
3
=27.68 g/cm
3
=27 680 kg/m
3
=1000 kg/m
3
=1 kg/L
1 lb/ft
3
=0.0160 g/cm
3
=16.02 kg/m
3
=62.43 lb/ft
3
=8.345 lb/US gal
=0.0160 kg/L
1 kg/m
3
=0.062 43 lb/ft
3
Specific gravity relative to water
1
m
g/m
3
=4.37 x 10
-7
grains/ft
3
(SGW) of 1.00=62.43 lb/ft
3
at 4°C or 39.2°F*
Specific gravity relative to dry air
(SGA) of 1.00=0.0765 lb/ft
3
=1.225 kg/m
3
1 lb/US gal=7.481 lb/ft
3
=0.1198 kg/L
1 g/ft
3
=35.3 x 10
6
m
g/m
3
1 lb/1000 ft
3
=16 x 10
6
m
g/m
3
Energy, Heat and Work:
1 cal=0.003968 Btu
3413 Btu=1 kW h
1 kcal=3.968 Btu=1000 cal=4187 J
1 Btu=0.2931 W h
=0.004187 MJ
=252.0 cal=0.252 kcal
1 J=0.000948 Btu=0.239 cal=1 W s
=778 ft lb
=1 N m =10
7
erg=10
7
dyne cm
=1055 J=0.001055 MJ=1.055 GJ
1 W h=0.85483 kcal (Intl Table)
1 ft lb=0.1383 kg m=1.356 J
1 hp hr=1.98 x 10
6
ft lb
1 therm=1.00 x 10
5
Btu
1 bhp (boiler horsepower)=33 475 Btu/hr
=8439 kcal/h=9.81 kW
Heat Content and Specific Heat:
1 cal/g=1.80 Btu/lb=4187 J/kg
1 Btu/lb=0.5556 cal/g=0.5556 kcal/kg
1 cal/cm
3
=112.4 Btu/ft
3
=2326 J/kg
1 kcal/m
3
=0.1124 Btu/ft
3
=4187 J/m
3
1 Btu/ft
3
=0.00890 cal/cm
3
=8.899 kcal/m
3
=0.0373 MJ/m
3
1 cal/g °C =1 Btu/lb °F=4187 J/kg K
1 Btu/US gal=0.666 kcal/L
1 Btu/lb °F=1 cal/g °C=4187 J/kg K
Heat Flow, Power:
1 N m/s=1W=1J/s
1 Btu/hr=0.2520 kcal/h
=0.001341 hp=0.7376 ft lb/sec
=0.000393 1 hp
1 kcal/h=1.162 J/s=1.162 W
=0.2931 W=0.2931 J/s
=3.968 Btu/hr
1 hp=33 000 ft lb/min=550 ft lb/sec
=0.001 Thermies/heure
=745.7 W=745 J/s
1 kW=1000 J/s=3413 Btu/hr=1.341 hp
=641.4 kcal/h
=660.6 kcal/hr
1 boiler hp=33 475 Btu/hr=34.5 lb
1 MW=3413000 Btu/hr
steam/hr from and at 212 F
Heat Flux and Heat Transfer Coefficient:
1 cal/cm
2
s=3.687 Btu/ft
2
sec
1 Btu/ft
2
sec=0.2713 cal/cm
2
s
=41.87 kW/m
2
1 Btu/ft
2
hr=0.003153 kW/m
2
1 cal/cm
2
h=1.082 W/ft
2
=11.65 W/m
2
=2.713 kcal/m
2
h
1 kW/m
2
=317.2 Btu/ft
2
hr
1 kW/ft
2
=924.2 cal/cm
2
h
* 62.35 lb/ft
3
at 60°F, 15.6°C; 8.335 lb/USgal.
Unit Equivalents
Continued on page xx Metric to American
American to Metric
Metric to Metric
American to American
1kWm
2
°C=1 kW/m
2
K
1 Btu/ft
2
hr °F=4.89 kcal/m
2
h °C
=176.2 Btu/ft
2
hr °F
=5.67 W/m
2
K
=860.4 kcal/hr m
2
°C
1 J/m
2
s K=0.1722 Btu/ft
2
hr °F
Length:
1 mm=0.10 cm=0.039 37 in.
1 in.=25.40 mm=2.540 cm=0.02540 m
=0.003 281 ft
1 ft=304.8 mm=30.48 cm=0.3048 m
1 m=100 cm=1000 mm=39.37 in.
1 mile=5280 ft; 1 nautical mile=6076 ft
=3.281 ft=1.094 yard
1 micron=1
m
=10
-6
m=1 micrometer
1 km=0.6214 mile
1 Angstrom unit=1 A
°
=10
-10
m
Pressure:
1N m
2
=0.001 kPa=1.00Pa
1 in. H
2
O*=0.2488 kPa=25.40 mm H
2
O
1 mm H
2
O=0.0098 kPa
=1.866 mm Hg
1 mm Hg=0.1333 kPa=13.60mm H
2
O
=0.00254 kg/cm
2
=2.540g/cm
2
=1 torr=0.01933 lb/in.
2
1 in. Hg=3.386 kPa=25.40 mm Hg
1 kg/cm
2
=98.07 kPa=10000 kg/m
2
=345.3 mm H
2
O=13.61 in H
2
O
=10000 mm H
2
O=394.1 in H
2
O
=7.858 oz/in.
2
=0.491 lb/in.
2
=735.6 mm Hg=28.96 in Hg
=25.4 torr
=227.6 oz/in.
2
=14.22 lb/in.
2
1 lb/in
2
=6.895 kPa=6895 N/m
2
=0.9807 bar
=703.1 mm H2O=27.71 in. H
2
O
1 bar=100.0 kPa=1.020 kg/cm
2
=51.72 mm Hg=2.036 in. Hg
10200 mm H
2
O=401.9 in. H
2
O
=16.00 oz/in.
2
750.1 mm Hg=29.53 in. Hg
=0.0703 kg/cm
2
=70.31 g/cm
2
=232.1 oz/in.
2
=14.50 lb/in.
2
=0.06897 bar
=100000 N/m
2
1 oz/in.
2
=0.4309 kPa
1 g/cm
2
=0.01422 lb/in.
2
=43.94 mm H
2
O=1.732 in. H
2
O
=0.2276 oz/in.
2
=3.232 mm Hg
=0.3937 in. H
2
O
=0.00439 kg/cm
2
=4.394 g/cm
2
(For rough calculations, 1 bar=1 atm=1 kg/cm
2
1 atm**=101.3 kPa=101325 N/m
2
=10 m H
2
O=100 kPa)
=10330 mm H
2
O=407.3 in. H
2
O
=760.0 mm Hg=29.92 in. Hg
=235.1 oz/in.
2
=14.70 lb/in.
2
=1.033 kg/cm
2
=1.013 bar
Temperature:
C=
5
/
9
(F-32)
F=(
9
/
5
) (K-290.93)
F=(
9
/
5
C) +32
K=C+273.15=(
5
/
9
)F+290.93
R=F+459.67
Thermal Conductivity:
1 W/m °K=0.5778 Btu ft/ft
2
hr °F
1 Btu ft/ft
2
hr °F=1.730 W/m K
=6.934 Btu in./ft
2
hr °F
=1.488 kcal/m h K
1 cal cm/cm
2
s °C=241.9 Btu ft/ft
2
hr °F
1 Btu in./ft
2
hr °F=0.1442 W/m K
=2903 Btu in./ft
2
hr °F
1 Btu ft/ft
2
hr °F=0.004139 cal cm/cm
2
s °C
=418.7 W/m K
1 Btu in./ft
2
hr °F=0.0003445 cal cm/cm
2
s °C
Thermal Diffusivity:
1 m
2
/s=38760 ft
2
/hr
1 ft
2
/hr=0.000025 8 m
2
/s=0.0929 m
2
/h
1 m
2
/h=10.77 ft
2
/hr
Torque (Bending Moment):
1 lb. (force) inch=0.11298 N m
1 lb in.=1.152 kg cm
1 lb ft=0.1383 kg m
*1"wc = 1"wg
**Normal atmosphere = 760 torr (mm Hg at 0°C)not a technical atmosphere, which is 736 torr or 1 kg/cm
2
. Subtract about
0.5 lb/in
2
for each 1000 ft above sea level.
Unit Equivalents (continued)
Continued on page xx Metric to American
American to Metric
Metric to Metric
American to American
Velocity:
1 cm/s=0.3937 in./sec=0.03281 ft/sec
1 in./sec=25.4 mm/s=0.0254 m/s
=10.00 mm/s=1.969 ft/min
=0.0568 mph
1 m/s=39.37 in./sec=3.281 ft/sec
1 ft/sec=304.8 mm/s=0.3048 m/s
=196.9 ft/min=2.237 mph
=0.6818 mph
=3.600 km/h=1.944 knot
1 ft/min=5.08 mm/s=0.00508 m/s
=0.0183 km/h
1 mph=0.4470 m/s=1.609 km/h
=1.467 ft/sec
1 knot=0.5144 m/s
1 rpm=0.1047 radians/sec
Viscosity, absolute,
m
:
0.1 Pa s=1 dyne s/cm
2
=360 kg/h m
1 lb mass/hr ft=0.000008634 lb force sec/ft
2
=1 poise=100 centipoise
=0.413 centipoise
=242.1 lb mass/hr ft =0.000413
Pa s
=0.002089 lb force sec/ft
2
1 lb force sec/ft
2
=115800 lb mass/hr ft
1 kg/h m=0.672 lb/hr ft=0.00278 g/s cm
=47880 centipoise
=0.00000581 lb force sec/ft
2
=47.88 Pa s
1 reyn=1 lb force sec/in
2
=6.890 x 10
6
centipoise
m
of air*=0.0180 centipoise
m
of water*=1.124 centipoise
=0.0436 lb/hr ft
=2.72 lb mass/hr ft
=3.763 x 10
-7
lb sec/ft
=2.349 x 10
-5
lb sec/ft
2
Viscosity, kinematic,
n
:
1 cm
2
/s=0.0001 m
2
/s
1 ft
2
/sec=3600 ft
2
/hr=92 900 centistokes
=1 stoke=100 centistokes
=0.0929 m2/s
=0.001076 ft
2
/sec
1 ft
2
/h=0.000 278 ft
2
/sec=25.8 centistokes
=3.874 ft
2
/hr
=0.000 025 8 m
2
/s
1 m
2
/s=3600 m
2
/h
=38 736 ft
2
/hr=10.76 ft
2
/sec
n
of water*=1.130 centistokes
n
of air*=14.69 centistokes
=32 SSU
=1.581 x 10
-4
ft
2
/sec
=1.216 x 10
-5
ft
2
/sec
Volume:**
1 cm
3
(cc)=0.00001 m
3
1 in.
3
=16.39 cm
3
=0.0001639 m
3
=0.0610 in.
3
=0.0338 US fluid oz
=0.01639 L
1 L (dm
3
)=0.0010 m
3
=1000 cm
3
1 ft
3
=1728 in.
3
=7.481 US gal
=61.02 in.
3
=0.035 31 ft
3
=6.229 Br gal
=0.2642 US gal
=28 320 cm
3
=0.02832 m
3
=28.32 L
=62.427 lb of 39.4°F (4°C) water
=62.344 lb of 60°F (15.6°C) water
1 m
3
=1000 L=1000000 cm
3
1 US gal=3785 cm
3
=0.003785 m
3
=61020 in.
3
=35.31 ft
3
=3.785 L=231.0 in.
3
=220.0 Br gal
=0.8327 Br gal=0.1337 ft
3
=6.290 bbl
=sp gr x 8.335 lb
=264.2 US gal
=8.335 lb of water
=1.308 yd
3
=
1
/
42
barrel (oil)
1 Br gal=277.4 in.
3
=0.004546 m
3
=4.546 L
=1.201 US gal
1 bbl, oil=9702 in.
3
=5.615 ft
3
=0.1590 m
3
=159.0 L
=42.00 US gal
=34.97 Br gal.
* At stp.
** Volume equivalents are for the same temperature and pressure in both sets of units.
A standard cubic foot or scfh is measured at 60 F and 29.92 Hg.
A standard cubic metre or sm
3
/h is measured at 15 C and 760 mm Hg.
A normal cubic metre or nm
3
/h is measured at 0 C and 760 m Hg.
Unit Equivalents (continued)
Continued on page xx Metric to American
American to Metric
Metric to Metric
American to American
Volume Flow Rate:*
1 cm
3
(cc)/s=1 x10
-6
m
3
/s
1 gpm (gal/min)=60.0 gph (gal/hr)
1 L/s=1x10
-3
m
3
/s
=0.01667 gps (gal/sec)
1 m
3
/h=4.403 US gpm (gal/min)
=0.00223 cfs (ft
3
/sec)
=0.5887 ft
3
/min
=8.022 cfh (ft
3
/hr)
=0.8326 Br gpm
=0.227 m
3
/h=0.06308 L/s
=1.429 bbl/hr=34.29 bbl/day
1 gph (gal/hr)=0.00105 L/s
=0.0000371 cfs (ft
3
/sec)
1 cfm (ft
3
/min)=6.18 Br gpm
=0.000471 m
3
/s
1 cfs (ft
3
/sec)=448.8 gpm
=22250 Br gph
Weight, Force, Mass:
1
m
g=1.544x10
-5
grains
1 oz avdp mass=28.35 g=0.02835 kg
=2.205x10
-9
lb avdp mass
1 lb avdp mass=453.6 g=0.4536 kg
1 g=0.03527 oz avdp mass
=4.536 x10
8
m
g
1 kg mass=1000 g mass
1 lb avdp force=0.4536 kg force
=35.27 oz avdp mass
=4.448 N
=2.205 lb avdp mass
1 lb=7000 grains
1 kg force=1000 g force=9.807 N
1 short ton=2000 lb=907.2 kg
=2.205 lb avdp force
1 long ton=2240 lb=1015.9 kg
1 metric ton=1000 kg=2205 lb
* Volume equivalents are for the same temperature and pressure in both sets of units.
A standard cubic foot or scfh is measured at 60°F and 29.92 Hg.
A standard cubic meter or sm
3
/h is measured at 15°C and 760 mm Hg.
A normal cubic meter or nm
3
/h is measured at 0°C and 760 m Hg.
Source:
North American Combustion Handbook, 3rd Edition, Vol. II, 1995.
Unit Equivalents (continued)