What size is my oil tank?
Almost every residential heating oil tank is one of seven standard sizes, and a tape measure identifies a visible one in under a minute. Without a tape, the data plate or an old delivery slip will tell you. A buried tank takes more work, and there is a route for that too.
To find what size heating oil tank you have, measure the oval end and the length. A 275 is 27 by 44 inches with a 60 inch length; a 330 shares that oval but runs 72 inches long. Buried steel tanks are 48 inches across, so the length separates a 550 from a 1000.
Measure it
Measure the width, height, and length of the tank and match the row below. Vertical means the oval end stands taller than it is wide; horizontal means it lies on its side.
| Tank | Dimensions (inches) | Chart |
|---|---|---|
| 275 vertical | 27 wide × 44 tall × 60 long | 275 vertical chart |
| 275 horizontal | 44 wide × 27 tall × 60 long | 275 horizontal chart |
| 330 vertical | 27 wide × 44 tall × 72 long | 330 vertical chart |
| 330 horizontal | 44 wide × 27 tall × 72 long | 330 horizontal chart |
| 550 buried | 48 diameter × 72 long | 550 underground chart |
| 1000 buried | 48 diameter × 130 long | 1000 underground chart |
| 500 buried (less common) | 48 diameter × 65 long | 500 underground chart |
The 275 and 330 share the same 27 × 44 oval end. The only visible difference is length: the 330 is 12 inches longer. If you can see the end but not the full length, measure along the top.
The table above covers the seven common sizes. For the small 120 to 240 gallon ovals, the Roth double-wall models, the fiberglass balls, and how deep a buried tank sits, see oil tank sizes and dimensions.
Read the data plate
Steel tanks carry a data plate on one end, stamped with the maker, the model, and the capacity. If yours is legible, believe it over any chart or estimate on this site. Most standard steel ovals are Granby; the Granby oil tank sizes and charts match a plate to a chart.
Check an old delivery slip
If the tank was empty or near empty when the truck came, the gallons on the ticket tell you the size. A delivery of 230 to 250 gallons says 275; around 280 to 300 gallons says 330. One old slip from a "we were almost out" winter answers the size question without a tape measure.
Buried tanks
A buried tank is out of reach, so you work from records and readings instead. Most are 550s or 1000s; true 500s and the fiberglass balls turn up less often. Four routes, in order of ease:
- Installation records. The installing oil company, prior owners, or your town's records often name the tank size outright.
- One delivery, two stick readings. Stick the tank before the truck comes, keep the ticket, stick it after. The buried tank size calculator turns those three numbers into the size, since the same two depths mean a different number of gallons in each tank.
- A full-tank stick reading. Right after a fill, stick the tank through the fill pipe. A depth near 48 inches says steel cylinder; about 62 or 76 inches says fiberglass ball.
- Fill-to-fill gallons. The gallons it takes to refill from a known low point separate a 550 from a 1000. Track one season of slips and you can tell them apart.
Common questions
What size heating oil tank do I have?
Measure the tank end and its length, then match the table above: 27 by 44 inches and 60 long is a 275, 27 by 44 and 72 long is a 330, and a 48 inch cylinder is a buried 500, 550 or 1000 depending on length. If the data plate on the tank end is legible, it settles the question and beats any chart.
My tank matches none of these sizes. What now?
Regional and legacy sizes exist, especially on older installations. Measure the width, height, and length (or diameter and length for a cylinder) and use the heating oil tank calculator, which turns your dimensions and a stick reading into gallons.
How do I tell a 275 from a 330 without a tape measure?
Use a delivery slip. Both tanks share the same oval end, so only length and capacity differ: a fill of 230 to 250 gallons into an empty tank says 275, while around 280 to 300 says 330. Failing that, the data plate on the tank end states the capacity.
How can I tell if my buried tank is a 550 or a 1000?
Both are 48-inch diameter cylinders, so stick readings look identical; the difference is length, and the length is buried. The cleanest answer is one delivery with a stick reading before and after, run through the buried tank size calculator. See the 550 chart and 1000 chart once you know.
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