This specific volume converter changes volume per unit mass between cubic meters per kilogram, cubic feet per pound, liters per kilogram, cubic centimeters per gram and related units. Specific volume is the reciprocal of density: v = 1/ρ. The SI unit is m³/kg; 1 L/kg = 0.001 m³/kg, and 1 ft³/lb is about 0.0624280 m³/kg.
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How to use the specific volume converter
- Enter the value, for example 0.85 from a table of air properties in m³/kg.
- In the specific volume converter, choose its unit and the target unit, such as m³/kg to ft³/lb.
- Read the specific volume converter result: 0.85 m³/kg = 13.62 ft³/lb.
For m³/kg to ft³/lb, multiply by 16.0185. Note that 1 L/kg equals 1 cm³/g.
What is specific volume?
Specific volume is volume per unit mass, the reciprocal of density, in cubic meters per kilogram. It is common in thermodynamics and steam tables.
Conversion formula
The specific volume converter stores every unit as a multiple of the base unit, the cubic meter per kilogram (m³/kg). To convert:
value in target unit = value × (factor of source unit ÷ factor of target unit)
where each factor is the size of the unit in cubic meters per kilogram.
Common specific volume conversions
| From | To | 1 unit equals |
|---|---|---|
| liter per kilogram (L/kg) | cubic meter per kilogram (m³/kg) | 0.001 m³/kg |
| cubic foot per pound (ft³/lb) | cubic meter per kilogram (m³/kg) | 0.06242796 m³/kg |
| cubic meter per kilogram (m³/kg) | liter per kilogram (L/kg) | 1,000 L/kg |
Specific volume converter worked example
Convert 25 liters per kilogram to cubic meters per kilogram:
- Factor of L/kg = 0.001 m³/kg
- Factor of m³/kg = 1 m³/kg
- 25 × 0.001 ÷ 1 = 0.025 m³/kg
Specific volume unit reference
| Unit | Symbol | Group | Equals (m³/kg) |
|---|---|---|---|
| Cubic Meter per Kilogram | m³/kg | SI | 1 |
| Liter per Kilogram | L/kg | Metric | 0.001 |
| Cubic Foot per Pound | ft³/lb | US/Imperial | 0.06242796058 |
| US Gallon per Pound | gal/lb | US | 0.008345404452 |
| Cubic Centimeter per Gram | cm³/g | Metric | 0.001 |
| Cubic Inch per Pound | in³/lb | US/Imperial | 3.61273 × 10−5 |
Reverse factors for each specific volume unit
The reference table gives each unit in cubic meter per kilograms. To go the other way, divide by that factor; the list below does the division for you.
- Liter per Kilogram (L/kg), Metric: 1 L/kg = 0.001 m³/kg, so 1 m³/kg = 1,000 L/kg.
- Cubic Foot per Pound (ft³/lb), US/Imperial: 1 ft³/lb = 0.06242796 m³/kg, so 1 m³/kg = 16.01846 ft³/lb.
- US Gallon per Pound (gal/lb), US: 1 gal/lb = 0.008345404 m³/kg, so 1 m³/kg = 119.8264 gal/lb.
- Cubic Centimeter per Gram (cm³/g), Metric: 1 cm³/g = 0.001 m³/kg, so 1 m³/kg = 1,000 cm³/g.
- Cubic Inch per Pound (in³/lb), US/Imperial: 1 in³/lb = 3.61273 × 10−5 m³/kg, so 1 m³/kg = 27,679.9 in³/lb.
Specific volume and density
Because v = 1/ρ, converting specific volume to density is a single division. A gas at 0.5 m³/kg has a density of 2 kg/m³. Specific volume of water and air, from typical densities:
| Substance (approximate) | Density (kg/m³) | Specific volume (m³/kg) | ft³/lb |
|---|---|---|---|
| Water (21 °C) | 998.02 | 0.001002 | 0.0161 |
| Water (4 °C) | 999.84 | 0.001 | 0.016 |
| Air (20 °C, 1 atm) | 1.2 | 0.830565 | 13.3044 |
| Ice (0 °C) | 917 | 0.001091 | 0.0175 |
Steam tables and psychrometric charts list specific volume because engineers track a fixed mass of fluid as it expands. For density units, use the density converter.
Where specific volume is used
Thermodynamics uses specific volume in the ideal gas law written per unit mass, p × v = Rspecific × T. HVAC work uses ft³ per pound of dry air from psychrometric charts to size fans and ducts. The common specific volume units are m³/kg in SI and ft³/lb in US customary work.
Steam and air examples
Steam tables are the place most people meet specific volume. Saturated steam at 100 °C and atmospheric pressure has a specific volume of about 1.672 m³/kg. Put that into the specific volume converter and you get roughly 26.8 ft³/lb, which is the figure older US tables print. At 10 bar absolute the same steam shrinks to about 0.194 m³/kg, so a pipe sized for low-pressure steam carries far more mass once the pressure rises.
Air is the other common case. Dry air at 20 °C and sea-level pressure has a density near 1.204 kg/m³, so its specific volume is about 0.831 m³/kg, or 13.3 ft³/lb. HVAC engineers read that number straight off a psychrometric chart, where it is printed as cubic feet per pound of dry air. When a fan moves 2,000 ft³/min, dividing by 13.3 gives about 150 lb of air per minute, and that mass flow is what drives heating and cooling loads.
Keep the state in mind. A specific volume converter only changes units; it cannot tell you the value at a new temperature or pressure. For that you need a steam table, the ideal gas law, or measured data, and then you convert the answer.
Related converters and calculators
Related property converters:
- Density converter: kg/m³ and g/cm³
- Density calculator: from mass and volume
- Specific heat capacity converter: J/(kg·K)
- Volume converter: m³, L and ft³
Sources
NIST Special Publication 811, Appendix B; USGS Water Science School: Water density.
Questions about this calculator
What is specific volume?
Volume per unit mass, the reciprocal of density. Its SI unit is m³/kg.
How do I convert m³/kg to ft³/lb?
Multiply by 16.0185. For example, 0.1 m³/kg = 1.6018 ft³/lb.
How do I convert ft³/lb to m³/kg?
Multiply by 0.0624280. For example, 13 ft³/lb = 0.8116 m³/kg.
How do I get density from specific volume?
Take the reciprocal: ρ = 1/v. A specific volume of 0.001 m³/kg means a density of 1,000 kg/m³.
What is the specific volume of water?
About 0.001002 m³/kg at 21 °C (1.002 L/kg), since water is about 998.0 kg/m³ there.
Is L/kg the same as cm³/g?
Yes. Both equal 0.001 m³/kg.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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