Propane Usage Calculator
Last updated: September 3, 2026
Appliances — set realistic burner hours per day
How this calculator works
Every appliance has an input rating in BTU/h — the rate it consumes propane while the burner is actually on. Multiply by your estimated burner hours per day (a furnace "runs" only while calling for heat; a gas-mode absorption fridge burns continuously) to get BTU per day:
gallons/day = Σ (BTU/h × hours/day) ÷ 91,502 · pounds/day = gallons × 4.2
Tank autonomy = usable tank gallons ÷ gallons per day. Usable gallons already include the DOT 80% fill rule (20 lb → 4.7 gal, 30 lb → 7 gal, 40 lb → 9.4 gal; see propane tank sizes).
Worked example
Fridge on gas (1,400 BTU/h × 24 h = 33,600), water heater (10,200 × 1 h), cooktop (7,500 × 0.75 h), furnace (35,000 × 3 h) → ≈150,150 BTU/day ≈ 1.64 gal/day ≈ 6.9 lb/day. A 30 lb tank (7 gal) lasts ≈ 4.3 days; two 30 lb tanks stretch that past a week of cool-weather camping.
Assumptions & sources
- 91,502 BTU/gal and 4.2 lb/gal: propane industry standard energy content; supplier pages (e.g., Ferrellgas, Foster Fuels) round to 91,500.
- Appliance input ratings: typical nameplate values — Atwood/Dometic 8535-class furnace 35,000 BTU/h input, Suburban 6-gal water heater ≈10,200 BTU/h, 2-way absorption fridges ≈1,200–1,600 BTU/h. Check your appliance's plate.
- 80% fill rule for DOT cylinders: standard practice; onboard ASME tanks also use usable-capacity figures.
- Furnace "hours" are burner-on hours. Milder weather or a thermostat set lower reduces them; −10 °C nights can double them.