Oil Tank Sizes: Dimensions and Charts for 275 to 1,000 Gallon Tanks

Oil tank sizes at a glance

The dimensions are the tank sizes each chart is built on; for the two ovals the charts use a slightly longer effective length, explained in their sections. A nominal size is a label, and tanks sold under the same label vary by maker, so measure yours before trusting any chart, including these. The round-tank charts treat the ends as flat, the same assumption our Tank Strapping Chart Generator makes; if your tank has dished or domed heads, its manufacturer's chart is the one to trust.

How to read the charts and your gauge

Every chart starts at the inside bottom of the tank. Find your oil depth in inches, read across, and you have gallons.

For its preset tanks, our heating oil usage calculator reads a float gauge's 1/4, 1/2 and 3/4 marks as fractions of the tank's height, and the gauge tables below do the same; if your gauge or stick gives inches, use the chart directly.

The rounded bottom and top of a tank hold less oil per inch than its middle, so the bottom quarter of the height holds well under a quarter of the oil. On a standing 275, a gauge at 1/4 means 11 inches of oil and about 58.2 gallons, not the 68.75 you get by dividing 275 by four.

Maine DEP's tank checklist asks whether the gauge is cracked, stuck or frozen, or shows oil or staining around it. If yours does, call your oil company, and measure the depth to use with the chart in the meantime.

275 gallon oil tank

Ace Tank's capacity chart gives the 275 as a 27 by 44 inch oval, 60 inches long, reaching 274 gallons at 44 inches. The Mike Raymond & Sons conversion chart lists it two ways: standing, with 44 inches of depth, or lying on its side with 27.

The charts use an effective interior length of 61.3 inches rather than 60, the length at which the oval geometry reaches about 273.7 gallons, close to Ace's 274. Near the middle of a standing 275, each inch holds about 7.2 gallons.

330 gallon oil tank

The 330 keeps the 275's 27 by 44 inch oval end and stretches it to 72 inches. Ace's chart puts it at 329 gallons at 44 inches, and Mike Raymond & Sons lists it standing or lying.

Here the effective length is 73.6 inches, which brings the calculation to 328.7 gallons. Every inch of length is worth about 4.5 gallons on this tank, so a few inches of difference between makers adds up.

500 gallon oil tank

The 500 is a round tank. Our chart uses 48 by 64 inches, the 500 gallon size in our tank calculators, which works out to 501.3 gallons. The Mike Raymond & Sons chart lists its 500 gallon round tank at 48 by 65 inches, and that chart ends at 509 gallons, so check your tank's length before relying on either.

550 gallon oil tank

The Mike Raymond & Sons chart lists the 550 as a 48 by 72 inch round tank. A calibration chart Seal-Rite publishes for its own 550 gallon horizontal tank, a sealer tank rather than an oil tank, gives the same 48.0 by 72.0 inches and 564.0 gallons.

That 564 is the flat-end geometry, which our chart reproduces at 564.0 gallons, while the Mike Raymond & Sons chart ends at 550 on its 48 inch row. Find out which convention your oil company's chart follows before comparing a delivery ticket against it.

1,000 gallon oil tank

Our chart uses 48 by 128 inches, the 1,000 gallon size in our tank calculators, which comes to 1,002.7 gallons. Mike Raymond & Sons lists its 1,000 gallon round tank at 48 by 130 inches, yet its chart ends at exactly 1,000, so two tanks sold as 1,000 gallons can differ by a few inches of length.

Near mid-depth each inch of oil is worth about 26.6 gallons on this tank, so a small error in a stick reading moves the total more than it does on the smaller sizes.

Full vs usable capacity

Every capacity figure on this page is a brim number, with oil right up to the top of the shell. No tank is filled or emptied that way.

At the top, a delivery ends when the vent alarm goes quiet. The Maryland Department of the Environment describes the alarm as a small device, usually a tube, typically installed between the tank and the vent pipe, that whistles while displaced air rushes past and falls silent once the oil reaches the end of the tube. Any space above that point stays empty. Maine DEP's checklist adds that a blocked vent can cause a silent overfill whistle: check for ice, snow or insect nests, or ask your delivery driver if you are not sure. MDE also suggests asking your dealer whether an alarm is installed at all.

At the bottom, oil shares the tank with whatever water and sludge have settled out. Maine DEP ranks corrosion from water and sludge build-up first among the top three causes of the home heating oil tank spills it responds to, and notes that a bottom outlet minimizes trapped water. Plan reorders around the oil above that layer, not the brim number.

Signs a tank needs replacing

Maine DEP presents its checklist items as signs a tank may be in danger of leaking, and says that if any apply, you should call a licensed oil heat technician or your fuel supplier to schedule a checkup. What to watch for also depends on where the tank sits.

• Rust, weeps, wet spots, excessive dents or patches on the tank surface (Maine DEP).
• Drips or other signs of leakage around the filter, valves or fittings (Maine DEP).
• Leak signs for any tank, from Connecticut DEEP's list: water in the tank, an unexplained increase in fuel use, a heating oil odor, and oil or withered or dead grass and plants near the tank, fill or vent pipes.
• Age: Maine DEP flags steel tanks more than 25 years old and says to start planning a replacement once a tank passes 20. Connecticut DEEP puts outside aboveground tanks at about 25 years, depending on conditions, unprotected steel underground tanks at about 15, and fiberglass, cathodically protected or steel-clad composite tanks at beyond their 30 year warranties.

Replacing or removing an oil tank

A failing tank that will be swapped for a new one is a replacement job; an old tank leaving service for good is a removal job. Our oil tank replacement guide covers sizing and installation, and the oil tank removal guide covers taking the old tank out. To compare prices, find contractors in your state or request free quotes.

Federal underground storage tank rules exclude a tank storing heating oil for consumptive use on the premises where it is stored, under the UST definition in 40 CFR 280.12. Check your state and town requirements before you remove or abandon a buried tank.

For a tank this page does not cover, the Tank Strapping Chart Generator builds a chart from your own measurements, and the tank volume calculator handles other shapes.