How the LPG Liquid Converter Works
The LPG Liquid Converter divides liquefied petroleum gas (LPG) mass by liquid density for the propane-butane mix. The default 0.54 kg/L fits a 60/40 autogas blend at 15°C (59°F).
Know the mix
Northern Europe sells propane-rich LPG; Southern Europe and Asia sell butane-rich LPG.
Find the liquid density
Read the density for the mix in the table below.
Enter the mass
Type the LPG weight in kilograms from the cylinder label or weighbridge.
Read the liquid liters
Tanks fill to 80–85% of water capacity to leave vapor space.
LPG Liquid Converter Formula
The LPG mix density formula is 1 ÷ ρmix = wpropane ÷ 0.508 + wbutane ÷ 0.584 at 15°C, with w as mass fractions.
- wC3
- Propane mass fraction
- wC4
- Butane mass fraction
Worked Examples
- 60/40 autogas: ρ = 1 ÷ (0.6/0.508 + 0.4/0.584) = 0.5359 kg/L.
- Car tank of 40 kg: 40 ÷ 0.536 = 74.6 L of liquid.
- 80% fill rule: a 100 L water-capacity tank holds 80 L, or 42.9 kg of 60/40 LPG.
LPG Liquid Converter Conversion Table
A 60/40 propane-butane LPG mix weighs 0.536 kg/L as a liquid at 15°C. The table lists 7 LPG compositions.
| Composition (by mass) | Liquid Density (kg/L) | Liters per 1 kg | Liters per 12.5 kg | kg per 100 L Tank at 80% |
|---|---|---|---|---|
| 100% propane / 0% butane | 0.508 | 1.969 | 24.61 | 40.6 |
| 80% propane / 20% butane | 0.522 | 1.917 | 23.97 | 41.7 |
| 70% propane / 30% butane | 0.529 | 1.892 | 23.65 | 42.3 |
| 60% propane / 40% butane | 0.536 | 1.866 | 23.33 | 42.9 |
| 50% propane / 50% butane | 0.543 | 1.840 | 23.01 | 43.5 |
| 30% propane / 70% butane | 0.559 | 1.789 | 22.36 | 44.7 |
| 0% propane / 100% butane | 0.584 | 1.712 | 21.40 | 46.7 |
What is an LPG Liquid Converter?
An LPG Liquid Converter is a calculator that converts LPG mass into liquid volume using the density of the propane and butane mix.
Liquefied petroleum gas is propane, butane or a mix, stored as a liquid under its own vapor pressure. Propane boils at −42°C (−44°F) and butane at −0.5°C (31°F).
LPG is sold by kilogram in cylinders and by liter at autogas pumps. EN 589 sets autogas quality in Europe, including vapor pressure limits that control the propane share by season.
What are the Uses of an LPG Liquid Converter?
There are 4 main uses of an LPG Liquid Converter.
Autogas pricing
Drivers compare €/L at the pump with €/kg for cylinders.
Tank filling limits
Fillers stop at 80% water capacity.
Bulk deliveries
Distributors convert tanker tonnes into customer liters.
Cylinder exchange
Retailers convert cylinder kg into usable liquid liters.