How the Propane Converter Works
The Propane Converter divides propane mass by liquid propane density. The default 0.493 kg/L fits liquid propane at 25°C (77°F) under its own vapor pressure.
Enter the propane mass
Type the net propane weight: 9.07 kg for a 20 lb BBQ cylinder.
Match the temperature
Liquid propane weighs 0.528 kg/L at 0°C and 0.468 kg/L at 40°C.
Read the liquid liters
Multiply by 0.264 for US gallons.
Check vapor volume
The table lists the gas volume the same mass produces at 15°C.
Propane Converter Formula
The propane liquid formula is Vliquid = m ÷ ρliquid(T). As a gas, 1 kg of propane fills about 0.536 m³ at 15°C and 1 atm.
- 44.1
- Molar mass of propane (C₃H₈), g/mol
- 23.645
- Molar volume of an ideal gas at 15°C and 1 atm, L/mol
Worked Examples
- 20 lb (9.07 kg) cylinder: 9.07 ÷ 0.493 = 18.40 L (4.86 US gal).
- Vapor: 9.07 kg × 536 L/kg = 4,862 L (4.86 m³) of gas.
- Cold day: 9.07 kg ÷ 0.528 = 17.18 L of liquid at 0°C.
Propane Converter Conversion Table
A 20 lb (9.07 kg) propane cylinder holds about 18.4 liters (4.9 US gal) of liquid at 25°C. The table converts common cylinder sizes.
| Cylinder | Propane Mass | Liquid at 25°C (L) | Liquid (US gal) | Gas at 15°C (m³) | Energy (kWh) |
|---|---|---|---|---|---|
| 1 lb camping cylinder | 0.45 kg (1.0 lb) | 0.92 | 0.24 | 0.24 | 5.9 |
| 5 kg | 5.00 kg (11.0 lb) | 10.14 | 2.68 | 2.68 | 64.5 |
| 20 lb BBQ | 9.07 kg (20.0 lb) | 18.40 | 4.86 | 4.86 | 117.0 |
| 11 kg | 11.00 kg (24.3 lb) | 22.31 | 5.89 | 5.90 | 141.9 |
| 13 kg | 13.00 kg (28.7 lb) | 26.37 | 6.97 | 6.97 | 167.7 |
| 30 lb | 13.60 kg (30.0 lb) | 27.59 | 7.29 | 7.29 | 175.4 |
| 19 kg forklift | 19.00 kg (41.9 lb) | 38.54 | 10.18 | 10.18 | 245.1 |
| 47 kg | 47.00 kg (103.6 lb) | 95.33 | 25.18 | 25.19 | 606.3 |
| 100 lb | 45.40 kg (100.1 lb) | 92.09 | 24.33 | 24.33 | 585.7 |
Energy uses a net calorific value of 12.9 kWh per kg (46.4 MJ/kg).
What is a Propane Converter?
A Propane Converter is a calculator that converts propane mass into liquid volume, with the gas volume shown for reference.
Propane (C₃H₈) stays liquid in a cylinder at about 8.4 bar (122 psi) absolute pressure at 20°C. Opening the valve drops the pressure, and liquid boils into gas for the burner.
Liquid propane expands about 0.27% per °C (1.5% per 10°F), several times more than water. Fill limits leave vapor space so a cylinder never fills with liquid on a hot day.
What are the Uses of a Propane Converter?
There are 4 main uses of a Propane Converter.
Grill cylinders
Users check remaining fuel by weighing the cylinder.
Home tank orders
Owners convert gallons delivered into kg and kWh.
Forklift fleets
Managers convert 19 kg cylinders into running hours.
Heating cost comparisons
Buyers compare propane per kWh with heating oil.