Convert propane pounds to gallons or gallons to pounds, or estimate how many gallons are in a propane tank from its size and gauge reading.

Fuel only; exclude cylinder or tank tare.

Typical liquid propane at 60°F. Warmer propane is less dense.

Heating-value basis
Typical gross (higher) heating value; fuel energy, not appliance output.

Understanding Propane Volume

This calculator converts net liquid propane weight to liquid volume, liquid volume to weight, or tank water capacity and gauge percentage to estimated contents. Enter a verified liquid density in lb per US liquid gallon. It does not solve for density, model vapor or infer a safe filling limit. Density varies with temperature and composition.

Core Formula

PV = (PM) / (PD)

Rearranged forms:

PM = PV × PD
PD = (PM) / (PV)
Variable Meaning Common Units
PV Propane volume m³, ft³, L, gal
PM Propane mass kg, lb
PD Propane density kg/m³, lb/ft³

How to Use the Calculator

  1. Choose liquid volume from weight, weight from liquid volume, or tank contents from water capacity and gauge. Enter the required quantity; liquid density starts at a typical 4.2 lb/US gal. In tank mode, pick a tank size and enter the gauge reading; maximum fill defaults to 80%.
  2. Select the input unit beside the quantity. Density is entered in lb/US gal; the calculator handles the stated mass and volume unit conversions.
  3. Choose the output volume unit you want: m³, ft³, liters, or gallons.
  4. If the result looks unrealistic, verify the liquid density, temperature, composition and net fuel quantity. This tool does not model propane vapor.

Example 1: Find Propane Volume

For a custom-density example, net propane mass is 500 kg and verified liquid density is 493 kg/m³. Enter 500 kg, approximately 4.114284 lb/US gal, and choose m³. This custom assumption differs from the default 60°F planning basis:

PV = (500) / (493) = 1.014 m³

This is about 1,014 liters.

Example 2: Find Propane Mass

Using the same custom liquid-density assumption, enter 2.5 m³ and approximately 4.114284 lb/US gal (493 kg/m³):

PM = 2.5 × 493 = 1232.5 kg

Quick Unit Reference

From To Factor
m³ liters 1000
m³ US gallons 264.172
ft³ liters 28.3168
ft³ US gallons 7.48052

When Density Matters Most

Situation Best Input Choice
Propane stored as liquid in a tank Use liquid propane density for the expected temperature
Propane vapor in a pipe or vessel Use a separate vapor model with actual pressure and temperature; this calculator is liquid-only
Unknown operating conditions Do not assume a single density value without checking the state and temperature

Common Mistakes

  • Mixing metric and imperial units in the same calculation.
  • Using vapor density when the propane is actually stored as a liquid.
  • Assuming tank size and propane volume are automatically the same thing.
  • Ignoring temperature effects on density.
  • Rounding density too aggressively before calculating large volumes.

Practical Notes

This calculator returns liquid volume and net fuel mass, not a permitted fill quantity. PERC’s Technical Pocket Guide, Table 1A, supplies the approximate 4.2 lb/US gal at 60°F and 91,502 BTU/US gal planning defaults. The energy figure uses a gross/HHV planning interpretation, not LHV or useful appliance output; PERC labels it total heating value after vaporization. The values remain editable. Energy equivalents use 1 BTU IT = 1055.05585262 J and 1 kWh = 3,600,000 J. Confirm tank gauge interpretation and any planning ceiling with the supplier; an example 80% is not universal fill authorization.