Cost to fill an oil or propane tank
A delivery costs the gallons that fit between your gauge reading and the fill line, times the price per gallon. The tables below do that sum for the common tank sizes at three starting levels. The prices are Maine's statewide averages for October 5, 2026 (oil $5.97, propane $3.46 a gallon). Type in your own quote and the dollars update.
Heating oil tanks
Oil tanks are named by label size, and a delivery stops at about 90% of it (my assumption; check the marking on your tank). Each cell is the gallons delivered and the cost at $5.97 a gallon.
| Tank | Fill line | From 10% (nearly empty) | From 25% (a quarter) | From 50% (half) |
|---|---|---|---|---|
| 275 gal | 247 gal | 219.5 gal $1,310 | 178.3 gal $1,064 | 109.5 gal $654 |
| 330 gal | 297 gal | 264 gal $1,576 | 214.5 gal $1,281 | 132 gal $788 |
| 550 gal | 495 gal | 440 gal $2,627 | 357.5 gal $2,134 | 220 gal $1,313 |
| 1,000 gal | 900 gal | 800 gal $4,776 | 650 gal $3,881 | 400 gal $2,388 |
Propane tanks
Propane tanks are filled to 80% of the water capacity, and the gauge shows percent of the same number. A 500 gallon tank therefore takes at most 400 gallons. Each cell is the gallons delivered and the cost at $3.46 a gallon.
| Tank | Fill line | Gauge 10% | Gauge 25% | Gauge 50% |
|---|---|---|---|---|
| 120 gal | 96 gal | 84 gal $291 | 66 gal $228 | 36 gal $125 |
| 250 gal | 200 gal | 175 gal $606 | 137.5 gal $476 | 75 gal $260 |
| 325 gal | 260 gal | 227.5 gal $787 | 178.8 gal $618 | 97.5 gal $337 |
| 500 gal | 400 gal | 350 gal $1,211 | 275 gal $952 | 150 gal $519 |
| 1,000 gal | 800 gal | 700 gal $2,422 | 550 gal $1,903 | 300 gal $1,038 |
Worked example
- A 275 gallon oil tank at a quarter full holds 275 × 25 ÷ 100 = 68.75 gal. A delivery stops at 247 gal, so it brings 178.25 gal. At $5.97 that is $1,064.
- A 500 gallon propane tank with the gauge at 25% holds 125 gal. The fill line is 500 × 80 ÷ 100 = 400 gal, so it takes 275 gal. At $3.46 that is $952.
Costs are rounded to the dollar. A dealer's bill can differ by the fee, a minimum order, a discount for volume, or the actual gallons metered.
Why a fill rarely matches the label
A 275 gallon oil tank is never filled to 275. It leaves air space at the top, and some are marked with a maximum near 247 gal; the 275 gallon oil tank chart has the details and the gallons at every inch of dip. Propane stops at 80% so the liquid has room to expand when it warms up, which the propane tank percentage chart explains. Multiplying the label size by the price overstates the bill. Starting from a higher level cuts it further, because you only pay for what the tank can still take.
Prices come from the Maine Department of Energy Resources heating fuel prices (oil is a cash price; propane is for households using 900 gallons or more a year). Yours will differ by region and dealer. This page is arithmetic on the numbers you enter and is no advice on when to buy.
Related pages
- Heating fuel cost comparison: oil, propane, gas, electricity and wood per million Btu.
- 500 gallon propane tank chart: gallons by gauge percent.
- How long will heating oil last: what the gallons mean in days.