Home Oil Tank Sizes: 275, 330 and More
From the Alcus family · Alcus Fuel Oil & Sons, Amityville · Updated October 31, 2026
Most Long Island basements have a 275-gallon oil tank. Some homes have a 330, a 550 or two tanks. Here's what that means when you order.
Common home tank sizes
| Tank | Usable when full | Left at 1/4 | Typical fill at 1/4 |
|---|---|---|---|
| 275 gallon (most common) | ≈ 225–250 gal | ≈ 55–65 gal | ≈ 165–190 gal |
| 330 gallon | about 20% more at each mark | — | — |
Estimates. Tank shape and how level it sits change the numbers. A 275 is usually an oval tank about 5 ft long; a 330 is about 6 ft. If you're not sure, the size is often stamped on a label on the tank.
Why a 275 doesn't take 275 gallons
Tanks need room at the top for expansion and to keep oil from backing up out of the vent, and the very bottom holds sediment you don't want drawn into the burner. That's why "full" is about 225–250 usable gallons in a 275, and why you should never wait until it's empty. See how to read your oil tank gauge.
How much to order
- Order at 1/4. On a 275 that's usually 165–190 gallons, comfortably in the 150+ gallon price tier.
- Not sure? Choose "fill my tank" and pay only for what's delivered, or try the heating oil calculator. Today's cost for common fills: cost to fill a 275-gallon tank.
- Tight month? Our minimum is 25 gallons: small deliveries.
Signs your tank needs attention
- Wet spots, drips or "weeping" on the bottom of the tank
- Heavy rust, flaking or bulging
- Oil smell around the tank, or leaks at the filter and fittings
- Rusted or unstable legs
- A gauge that's cracked, stuck or leaking
Oil on the floor? Follow our oil leak steps now. For an aging tank, see oil tank replacement. Smell oil after a delivery? See oil smell after delivery. Outdoor tank? See outdoor oil tanks in winter.
Need oil or service on the South Shore?
Questions
How much oil does a 275-gallon tank hold?
Not 275. Tanks are never filled to the brim, so a full 275-gallon tank usually holds about 225–250 gallons of usable oil.
How much should I order for a 275 tank at 1/4?
At 1/4 there are roughly 55–65 gallons left, so a fill-up usually takes about 165–190 gallons.
How long does a full 275-gallon tank last?
It depends on the house and the weather. A typical home uses 2–3 gallons a day in mild weather and 6–8 in a cold snap, so a full tank may last about a month in deep winter and much longer in fall or spring.
How do I know if my oil tank needs replacing?
Warning signs include wet spots or weeping on the bottom of the tank, heavy rust or flaking, oil smell near the tank, leaks at fittings or the filter, and wobbly or rusted legs. If you see oil on the floor, treat it as an emergency.