Specific Volume Converter
Convert specific volume between cubic metres per kilogram, cubic feet per pound, litres per kilogram and cubic centimetres per gram. Specific volume is the volume occupied by one unit of mass — the reciprocal of density. It is the natural quantity in thermodynamics, where working per unit mass keeps steam tables and gas calculations tidy. A substance twice as dense has half the specific volume, so if you know one you know the other.
How to use this tool
- Enter a specific volume value.
- Choose the unit you are converting from.
- Choose the unit you want the answer in.
- Read the result, or show every equivalent unit at once.
- To go from density, take its reciprocal first: 1 ÷ density gives specific volume.
The formula
Specific volume is the volume occupied per unit mass — the reciprocal of density. Its SI base unit is the cubic metre per kilogram. It appears throughout thermodynamics, where working per unit mass is natural.
specific_volume = 1 ÷ density
base_m³/kg = value × (m³/kg per unit)- v
- Specific volume, m³/kg
- ρ
- Density, kg/m³ — v = 1/ρ
Because specific volume is one over density, a substance twice as dense has half the specific volume. Water is about 0.001 m³/kg.
Worked examples
Water
- Given
- 0.001 m³/kg
- Result
- ≈ 0.016 ft³/lb
Water is about 1000 kg/m³, so its specific volume is 1/1000 = 0.001 m³/kg, which is roughly 0.016 cubic feet per pound.
From density
- Given
- Air ≈ 1.2 kg/m³
- Result
- ≈ 0.833 m³/kg
Specific volume is the reciprocal of density, so 1 ÷ 1.2 ≈ 0.833 m³/kg — a kilogram of air fills a lot of space.
Steam
- Given
- 1.6 m³/kg
- Result
- ≈ 25.6 ft³/lb
Low-pressure steam has a large specific volume, which is why steam plant is bulky at low pressures.
Frequently asked questions
It is the volume that one unit of mass of a substance occupies — cubic metres per kilogram in SI. It is exactly the reciprocal of density: if density is mass per volume, specific volume is volume per mass.
Take the reciprocal. If density is 800 kg/m³, specific volume is 1 ÷ 800 = 0.00125 m³/kg. Going back, density is 1 ÷ specific volume. The two always multiply to one.
Many thermodynamic relations are written per unit mass — internal energy, enthalpy and entropy all have “specific” per-kilogram forms. Using specific volume keeps everything on the same per-mass basis, which is why steam tables list it directly.
Gases and low-density materials. A kilogram of air at room conditions fills nearly a cubic metre, while a kilogram of water fills only a litre. Low-pressure steam has a very large specific volume, which matters when sizing pipes and vessels.
Yes. Cubic feet per pound converts exactly from cubic metres per kilogram, because the foot and pound have exact metric definitions. The tool keeps full internal precision and rounds only what it displays.
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