Heating Oil Usage Calculator
This heating oil usage calculator shows how long your oil will last. A burner that uses 1.0 gallon per hour and runs 6 hours a day burns 6 gallons a day, so 100 gallons last about 16.7 days.
Example: Calculate from: Burner firing rate (gal/h) · Oil in the tank 100 · Unit: gallons (US) · Firing rate 1 gal/h · Burner run time per day 6 h → Oil lasts: About 16.7 days (2.4 weeks) at 6 gal per day. Source: U.S. Energy Information Administration (EIA), Energy Explained: British thermal units (Btu) – sample Btu conversion factors, heating oil 1 gallon = 138,500 Btu (read 10.10.2026). Updated: .
How it is calculated
Days = oil in the tank ÷ (gallons per hour × burner hours per day). If you only know the input rating in Btu per hour, divide it by the heat content of heating oil: the U.S. Energy Information Administration (EIA) uses 138,500 Btu per gallon. A 140,000 Btu/h input therefore burns about 1.01 gallons per hour.
How long 100 gallons last at 1.0 gal/h
| Burner hours per day | Gallons per day | Days |
|---|---|---|
| 4 | 4 | 25 |
| 6 | 6 | 16.7 |
| 8 | 8 | 12.5 |
| 12 | 12 | 8.3 |
The run time is the key number: in mild weather the burner fires for a short time, on cold days much longer. The most reliable way to find your own use is to read the tank gauge on two days and divide the difference by the days in between, then use “Known use per day”.
Tips
- One U.S. gallon is 3.785 liters; switch the unit if your tank or delivery is in liters.
- Hot water from the same boiler adds to the daily use in summer too.
- Order before the tank runs low – the result is an estimate, not a gauge reading.
- Safety: an oil burner that is worn or poorly adjusted can release carbon monoxide (CO). The EPA advises having a trained professional inspect, clean and tune up the heating system, flues and chimney every year; the CPSC recommends CO alarms on each level of the home, outside each sleeping area.
Work out how much oil is in a horizontal tank with the tank volume calculator, and compare fuels with the heating cost comparison.
Frequently asked questions
How long will 100 gallons of heating oil last?
It depends on how long the burner runs. At 1.0 gallon per hour and 6 burner hours a day, 100 gallons last about 16.7 days; at 4 hours a day, 25 days.
How do I convert Btu/h to gallons per hour?
Divide by 138,500 Btu per gallon, the EIA heat content of heating oil. 140,000 Btu/h is about 1.01 gal/h.
How many Btu are in a gallon of heating oil?
The EIA lists 138,500 Btu per gallon of heating oil.
How do I measure my daily oil use?
Read the tank gauge on two dates, subtract and divide by the number of days. Enter that value under “Known use per day”.
How many liters is a gallon?
One U.S. gallon is 3.785 liters (NIST).
Sources and legal basis
- U.S. Energy Information Administration (EIA), Energy Explained: British thermal units (Btu) – sample Btu conversion factors, heating oil 1 gallon = 138,500 Btu (read 10.10.2026)
- U.S. EPA, Carbon Monoxide’s Impact on Indoor Air Quality – sources (poorly adjusted and maintained boilers, furnaces), annual professional inspection and tune-up, CPSC recommendation for CO alarms (read 10.10.2026)
- NIST SP 811, Appendix B.8: 1 gallon (U.S.) = 3.785 412 L (read 10.10.2026)
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