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How Long Will My Heating Oil Last?
Enter how much oil you have and how fast you burn it. You'll get the number of days left and the date to call your oil company, with a safety reserve built in.
Three ways to estimate your burn rate
1. You already know your gallons per day
If you have measured it, or the usage calculator worked it out from your delivery slips, enter it directly. Remember that it changes with the weather: a home that burns 1.5 gallons a day in October can burn 4 in a January cold snap.
2. From your last delivery
If the tank was filled to full on both of your last two deliveries, the second delivery put back exactly what you burned in between. Divide the gallons by the days between the deliveries. Example: 95 gallons delivered on January 30 after a fill on January 2 is 95 ÷ 28 = 3.4 gallons a day. This only reflects the weather during that stretch, so it overstates fall and spring use and can understate the coldest weeks.
3. From the weather (degree days)
Oil companies on automatic delivery predict your use with heating degree days. A day's degree days are 65 minus the day's average temperature, so a 30°F day is 35 degree days and a 65°F day is zero. Each home burns roughly one gallon per so many degree days. That number is the K-factor, and it is often printed on delivery tickets.
If you don't have your own K-factor, the default of 10.8 comes from the U.S. Energy Information Administration's 2025–26 Winter Fuels Outlook. EIA expected an average oil-heated household to use 399 gallons from November through March, against 4,296 heating degree days for the Northeast, where more than 80% of oil-heated homes are: 4,296 ÷ 399 ≈ 10.8. Because EIA's figure covers everything the oil is used for, including an oil-fired water heater, leave other oil use at zero when you use the default. A drafty or large house may be 6 or 7; a tight, smaller one 14 or more.
How long 100 gallons lasts
Using the average-home K-factor of 10.8 and no reserve:
| Average outdoor temp | Gallons per day | 50 gal | 100 gal | 150 gal | 200 gal |
|---|---|---|---|---|---|
| 50°F (mild fall) | 1.4 | 36 days | 72 days | 108 days | 144 days |
| 40°F | 2.3 | 22 days | 43 days | 65 days | 86 days |
| 30°F (typical January in the Northeast) | 3.3 | 15 days | 31 days | 46 days | 62 days |
| 20°F | 4.2 | 12 days | 24 days | 36 days | 48 days |
| 10°F (cold snap) | 5.1 | 10 days | 20 days | 29 days | 39 days |
The average home's numbers are a starting point. Your house could easily burn half or double these amounts.
Why keep a reserve?
Running out of oil costs more than the oil. Many burners need to be primed and restarted by a technician after the tank runs dry, and the last few inches of the tank are where water and sludge settle, which can clog the filter and nozzle. Deliveries also slow down during cold snaps and storms, which is exactly when you burn the most. That's why the calculator's main answer is the day you reach your reserve rather than the day you hit empty. A quarter tank is the usual rule of thumb; if your supplier needs a week's notice in January, set the reserve to at least a week of midwinter burn.
Tips for stretching the oil you have
Each degree you lower the thermostat cuts your burn a little, because it reduces the temperature gap the house loses heat across. A yearly burner cleaning and tune-up keeps efficiency up, and a clogged nozzle or dirty heat exchanger can waste a noticeable share of each gallon. Sealing obvious drafts around doors and the sill plate helps too. If your usage seems high for the weather, run your numbers through the usage calculator. If you're weighing a change of fuel, compare costs with the heat pump vs oil calculator.
Frequently asked questions
How long will 100 gallons of heating oil last?
For a typical oil-heated home, about 4 weeks in midwinter weather (average temperature near 25°F) and about 10 weeks in mild fall weather (around 50°F). At a steady 3 gallons a day, 100 gallons lasts 33 days. Your own burn rate is what matters, so use the calculator with your delivery history.
How long does a full 275 gallon tank last?
A full delivery into a 275 is usually 220 to 240 gallons. Keeping 50 gallons in reserve, that is roughly 6 to 9 weeks in January for an average home burning 3 to 4 gallons a day, and several months in spring or fall.
How long will a quarter tank of oil last?
A quarter of a 275 vertical tank is about 60 to 70 gallons. At 3 gallons a day that is roughly 3 weeks to empty, but a quarter tank is already the point where most suppliers suggest ordering, because delivery can take several days in a cold snap.
What is a K-factor on my oil delivery slip?
It is your home's degree days per gallon: how many heating degree days it takes you to burn one gallon. A higher number means a more efficient or smaller home. Automatic-delivery companies use it to schedule fills. If your slip shows one, enter it in the weather method.
How many gallons of heating oil does a house use per day?
It depends mostly on the outside temperature. EIA's numbers for an average oil-heated household work out to about 2 gallons a day in November and about 3 gallons a day in January. See the heating oil usage calculator to compare your own figure.
Sources
- U.S. Energy Information Administration, Winter Fuels Outlook 2025–26: 399 gallons November–March per heating-oil household, monthly consumption, Northeast heating degree days, definition of degree days (base 65°F).
Last reviewed October 25, 2026. Estimates only; see the disclaimer.