Units, Dimensions, Conversions

Units and Dimensions

Table C.1:
SI units with c.g.s. and British system equivalents

Quantity Dimensions SI c.g.s. British Basic         Length L 1 m = 102cm = 3.281 ft Mass M 1 kg = 103g = 2.205 lb Time T 1 s = 1 s = 2.778 x 10-4h Temperature 1 K = 1 K = 1.8 oF Derived         Area L2 1 m2 =104cm2 = 10.76 ft2 Volume L3 1 m3 = 106 cm3 = 35.31 ft3 Density M L-3 1 kg m-3 = 10-3 g cm-3 = 6.243 x 10-2 lb ft-3 Velocity L T-1 1 m s-1 = 102 cm s-1 = 3.281 ft s-1 Acceleration L T-2 1 m s-2 = 102 cm s-2 = 3.281 ft s-2 Force ML T-2 1 kg m s-2 = 105 g cm s-2 = 0.225 lb f     = 1 N (Newton) = 105 dynes (lb force) Pressure M L-1 T-2 1 kg m-1 s-2 = 10 g cm-1 s-2 = 0.021 lb f ft-2     = 1 Pa (Pascal) = 10-2 hPa (or mb)   Work, energy ML2 T-2 1 kg m2 s-2 = 107 g cm2 s-2 = 0.738 ft lb f     = 1 J (Joule) = 107 ergs   Power ML2 T-3 1 kg m2 s-3 = 107 g cm2 s-3 = 0.738 ft lb f s-1     = 1 W (Watt) = 107 ergs s-1   Heat, energy Q (= ML2 T-2 ) 1 J = 0.2388 cal = 9.487 x 10-4 BTU Heat flux QT-1 1 W = 0.2388 cal s-1 = 3.412 BTU h-1 Heat flux density QL-2 T-1 1 W m-2 = 2.388 x 10-5 = 0.317       cal cm-2 s-1 BTU ft-2 h-1 Latent heat QM-1 1 J kg-1 = 2.388 x 10-4 4.29 x 10-4       cal g-1 BTU lb-1 Specific heat QM-1 -1 1 J kg-1 K-1 = 2.388 x 10-4 = 2.388 x 10-4       cal g-1 K-1 BTU lb-1 o F-1 Thermal QL-1 -1 T-1 1 W m-1 K-1 = 2.388 x 10-3 = 0.578 conductivity     cal cm-1 s-1 K-1 BTU ft-1 h-1 o F-1 Thermal L2 T-1 1 m2 s-1 = 104 cm2 s-1 = 10.8 ft2 s-1 diffusivity

Useful Metric to English Conversions

Length:

1 kilometer (km) = 1000 meters (m) = 0.6214 miles (mi) = 3281 feet (ft) 


1 meter = 100 centimeters (cm) = 1.0936 yards (yd) = 3.281 feet = 39.37 inches (in) 


1 centimeter = 10 millimeters (mm) = 0.3937 inches 


1 micron (m)= 10-6 meters = 10-4 centimeters = 3.937 x 10-5 inches 

Area:

1 square kilometer (1 km2) = 106 sq. meters (m2)  = 0.3861 sq. miles (mi2)  = 247.1 acres 

1 m2 = 104 sq. centimeters (cm2) = 1.196 sq. yards = 10.764 sq. feet = 1550.0 sq. inches 

Volume:

1 cubic kilometer = 109 cubic meters (m3) = 0.2399 cubic miles 

1 cubic meter = 106 cubic centimeters = 1.308 cubic yards =  35.31 cubic feet = 61024 cubic inches 

1 litre (1) = 1000 cm3 = 10-3

cubic meters = 0.264 US gallons (US gal) = 61.024 in3
Mass: 		   

1 metric ton (tonne) = 1000 kilograms = 2204.6 avoirdupois pounds (means pound of mass not force) 

1 kilogram (kg) = 1000 grams (g) = 2.2046 avoirdupois pounds

Time:

1 day = 86400 seconds (s)  

1 year (yr) = 3.156 x 107 seconds 

Velocity:

1 meter/second (same as m/s, read meter per second) = 3.281 feet/second = 2.24 miles/hour 

Speed:

1 m/s = 3.6 kilometers /hour = 2.237 miles/hour 

1 kilometer/hour = 0.62 miles/hour (mi/hr) 

1 knot = 1 nautical mile/hour = 1.151 miles/hour = 0.51 m/s = 1.85 km/hr 

Force:

1 newton (N) =  1 kilogram meter/(sq. second) 

1 newton (N) = 1 kg m-1 s-2 = 0.2248 pounds force 

Pressure:

1 atmosphere  = 1013.2 hectopascals (hPa) = 101.32  kilopascals (kPa)

1 atmosphere  = 14.7 pounds/ sq. inch (lb/in2) 

1 atmosphere = 760 millimeters of mercury (mm Hg) =  29.92 inches of mercury 

10 millibars (hPa) = 1 kilopascal (kPa) 

1  Pascal (Pa) = 1 newton /meter2 = 0.01 millibars (mb) = 0.01 hectopascals (hPa) 

1 millibar (mb) = 1 hectopascal (hPa) 

Temperature: 
Temperature in  o C = 5/9(temperature in o F - 32) 

Temperature in  o F = 9/5(temperature in o C) + 32 

Temperature in   K = temperature in o C + 273.15 

Energy:

1 joule (J) = 1 newton meter (N m) = 1 kg m2 s-2 =  0.239 calories = 1 watt sec (W s) 

1 calorie (cal)= 4.186 joules (J) 

1 langley = 1 calorie /square centimeter 

1 kilowatt hour = 3.6 x 106J 

Power:

1 watt (W) = 1 joule / second  (J / s) =  14.3353 calories /minute (cal/min) 

1 calorie/second = 4.186 joules /second (J/s) = 4.186 watts (W) 

1 calorie/minute = 0.06973 watts (W) 

1 horsepower (hp) = 746 watts (W)