Specific Volume Converter
Convert between m³/kg, cm³/g, ft³/lb, and other specific volume units.
Specific Volume Converter
Enter a specific volume and select its unit — all other units update instantly.
Material Specific Volumes
How to Convert Between M³/Kg, Ft³/Lb, and Cm³/G
Your steam table lists specific volume at 0.001 m³/kg. Your plant specification uses ft³/lb. Type 0.001, select m³/kg, and see that it equals 0.01602 ft³/lb, 1.0 cm³/g, and 1.0 mL/g. The material reference confirms water at standard conditions is 0.001 m³/kg, so the numbers match.
The converter handles 9 units: m³/kg, cm³/g, mL/g, L/kg, L/g, ft³/lb, in³/lb, US gal/lb, and imp gal/lb. A thermodynamics student working with steam at 1.694 m³/kg sees it equals 27.14 ft³/lb and 1,694 L/kg. An HVAC engineer sizing a compressor for R-134a at 0.029 m³/kg sees it equals 0.4645 ft³/lb. The material reference shows air at 0.816 m³/kg to osmium at 0.0000443 m³/kg.
Why specific volume matters more than density in thermodynamics
Power plant engineers read steam tables that list specific volume (v) at each pressure and temperature. At 100°C and 1 atm, steam v = 1.694 m³/kg while liquid water v = 0.001 m³/kg. The ratio is 1,694:1. To convert steam flow from m³/s to kg/s, divide by specific volume: mass flow = volume flow / v. Using density instead of specific volume gives the wrong direction of conversion.
A refrigerator compressor must move enough R-134a vapour to absorb the required heat. The evaporator output is 0.029 m³/kg. To move 0.05 kg/s of refrigerant, the compressor needs 0.05 x 0.029 = 0.00145 m³/s = 5.22 m³/hr. If you use density (34.5 kg/m³) instead of specific volume, you calculate 0.05 / 34.5 = 0.00145 m³/s, which happens to give the same answer because v = 1/rho. But the mental model is different.
The ideal gas law in specific volume form is Pv = RT, where v is m³/kg. For air at 20°C and 1 atm: v = RT/P = (287 x 293) / 101325 = 0.831 m³/kg. This tells you 1 kg of air occupies 831 litres. If you instead use density (rho = P/RT = 1.204 kg/m³), you get the same information but in a less convenient form for gas flow calculations.
How the Specific Volume Converter Handles M³/Kg and Ft³/Lb
All conversions pass through cubic meters per kilogram (m³/kg). When you enter 1.694 m³/kg (steam at 100°C), the tool divides by each target unit's factor: by 0.062428 for ft³/lb, by 0.001 for cm³/g, by 1,000 for L/kg. The result: 1.694 m³/kg = 27.14 ft³/lb = 1,694 cm³/g = 1,694 L/kg.
Why cm³/g, mL/g, and L/kg give the same number
1 cm³/g = 1 mL/g (since 1 cm³ = 1 mL) = 1 L/kg (since 1 L = 1,000 cm³ and 1 kg = 1,000 g, the factors cancel). All three equal 0.001 m³/kg. This equivalence means you can read lab measurements in cm³/g and industrial specs in L/kg without conversion. The converter shows all three as identical values.
The imperial factor of 16.0185 in reverse
For density, 1 lb/ft³ = 16.0185 kg/m³. For specific volume (the reciprocal), 1 ft³/lb = 1/16.0185 = 0.062428 m³/kg. This factor comes from 1 lb = 0.45359237 kg and 1 ft = 0.3048 m: 1 ft³/lb = (0.3048)^3 / 0.45359237 = 0.0283168 / 0.45359237 = 0.062428. The converter stores this factor directly.
The dynamic formatting handles the full range from gases (air at 0.816 m³/kg) to dense metals (osmium at 0.0000443 m³/kg). Values below 10^-6 use scientific notation because they are too small for fixed decimal display. Values above 1,000 use locale-formatted numbers with commas for readability. This ensures you can read any value from any substance without losing precision.
Frequently Asked Questions
How do I convert 0.816 m³/kg to ft³/lb?
Divide by 0.062428: 0.816 / 0.062428 = 13.07 ft³/lb. This is the specific volume of air at sea level. For a quick estimate, multiply m³/kg by 16.02 to get ft³/lb (since 1/0.062428 = 16.02). The converter shows all units simultaneously so you can verify the relationship.
What is the specific volume of steam vs liquid water?
At 100°C and 1 atm: steam v = 1.694 m³/kg, liquid water v = 0.001 m³/kg. The ratio is 1,694:1. This means 1 kg of steam occupies 1,694 times more volume than 1 kg of liquid water. This enormous difference is why steam engines work: boiling water creates a massive volume increase that drives pistons.
Why do steam tables list specific volume instead of density?
Thermodynamic calculations use specific volume because it appears directly in the ideal gas law (Pv = RT) and in enthalpy/entropy calculations. When calculating steam flow through a pipe, you divide volume flow by specific volume to get mass flow. Using density would require an extra division step (mass flow = volume flow x density). Steam tables are designed for direct use.
How does pressure affect the specific volume of a gas?
For an ideal gas, specific volume is inversely proportional to pressure (v = RT/P). Doubling the pressure halves the specific volume. Real gases deviate from this at high pressures. At 1 atm and 20°C, air v = 0.831 m³/kg. At 10 atm, v = 0.0831 m³/kg. At 100 atm, v = 0.0081 m³/kg (deviation from ideal behavior starts to matter).
What is the specific volume of common materials?
Air: 0.816 m³/kg. Water: 0.001 m³/kg. Aluminum: 0.00037 m³/kg. Iron: 0.000127 m³/kg. Gold: 0.0000518 m³/kg. Osmium: 0.0000443 m³/kg. The material reference section in the converter shows these values. Notice that metals have very small specific volumes because they are dense.
How do I use specific volume to size a compressor?
A compressor must handle a specific volume flow rate (m³/s). Multiply the required mass flow rate (kg/s) by the specific volume at the compressor inlet. For R-134a at 0.029 m³/kg and 0.05 kg/s mass flow: volume flow = 0.05 x 0.029 = 0.00145 m³/s = 5.22 m³/hr. The compressor displacement must exceed this value.