550 Gallon Underground Oil Tank chart
Geometric capacity 551.8 gallons. Usually filled to ~500 gal. A 48 in diameter variant also exists — confirm your diameter before using this chart.
| Depth | Gallons | Liters | % Full |
|---|---|---|---|
| 1″ | 3 | 13 | 1% |
| 2″ | 10 | 36 | 2% |
| 3″ | 18 | 66 | 3% |
| 4″ | 27 | 101 | 5% |
| 5″ | 37 | 140 | 7% |
| 6″ | 48 | 183 | 9% |
| 7″ | 60 | 229 | 11% |
| 8″ | 73 | 277 | 13% |
| 9″ | 87 | 328 | 16% |
| 10″ | 101 | 381 | 18% |
| 11″ | 115 | 436 | 21% |
| 12″ | 130 | 492 | 24% |
| 13″ | 145 | 550 | 26% |
| 14″ | 161 | 609 | 29% |
| 15″ | 177 | 670 | 32% |
| 16″ | 193 | 731 | 35% |
| 17″ | 209 | 793 | 38% |
| 18″ | 226 | 855 | 41% |
| 19″ | 242 | 918 | 44% |
| 20″ | 259 | 981 | 47% |
| 21″ | 276 | 1,044 | 50% |
| 22″ | 293 | 1,108 | 53% |
| 23″ | 309 | 1,171 | 56% |
| 24″ | 326 | 1,234 | 59% |
| 25″ | 342 | 1,296 | 62% |
| 26″ | 359 | 1,358 | 65% |
| 27″ | 375 | 1,419 | 68% |
| 28″ | 391 | 1,479 | 71% |
| 29″ | 406 | 1,538 | 74% |
| 30″ | 422 | 1,596 | 76% |
| 31″ | 437 | 1,653 | 79% |
| 32″ | 451 | 1,708 | 82% |
| 33″ | 465 | 1,761 | 84% |
| 34″ | 478 | 1,811 | 87% |
| 35″ | 491 | 1,860 | 89% |
| 36″ | 503 | 1,906 | 91% |
| 37″ | 515 | 1,948 | 93% |
| 38″ | 525 | 1,988 | 95% |
| 39″ | 534 | 2,022 | 97% |
| 40″ | 542 | 2,052 | 98% |
| 41″ | 548 | 2,076 | 99% |
| 42″ | 552 | 2,089 | 100% |
How to stick this tank
Underground tanks are sticked through the fill pipe. Lower the stick until it rests on the tank bottom, then read the wet line — but remember the fill pipe riser adds length above the tank: your liquid depth is measured from the stick bottom to the wet line only, and it can never exceed the tank diameter. Two pro habits: smear water-finding paste on the bottom few inches of the stick once a season (it changes color if groundwater is intruding), and stick before and after a metered delivery once — if the chart agrees with the metered gallons, you've confirmed the tank size.
About this chart
Source geometry: 42 x 92 in variant per supplier gauge charts. Geometry yields 551 gal.. Values are computed with exact partial-fill formulas (see methodology) — a circular/obround segment for the shell.
FAQ
How many gallons are in my 550 gallon underground oil tank at half depth?
About 276 gallons. Use the stick reader above for any depth.
Where do I measure from?
From the inside bottom of the tank, straight up to the wet line on your stick. Keep the stick vertical.
Why does my manufacturer chart differ by a gallon or two?
Manufacturer charts account for that tank's exact head shape and fittings; this chart is exact for the stated geometry. Differences are typically 1–3%. Usually filled to ~500 gal. A 48 in diameter variant also exists — confirm your diameter before using this chart.