Heating Oil Usage Calculator
Turn your oil tank's float gauge into days: how many gallons a day your house burns this month by size and weather, when to order before you hit a quarter tank, when the tank runs dry, and what the month costs. Built on supplier burn rates per square foot and the real 240-gallon fill of a 275 tank.
A float gauge reads fractions of a tank that isn't even full when it says full. This turns it into days: what the house is burning this month, when to call before you hit a quarter tank, and what the month costs.
Your tank
Stamped on the tank's plate; 275 is the common indoor tank. A "full" tank holds about 12% less than its size — 240 gallons in a 275 — to leave room for air and sediment.
What the float gauge reads
The glass tube on top of the tank. It reads fractions of the tank, and it's coarse — go with the closest mark.
Your house and the weather
The part of the house the oil burner heats. A typical home is 1,500–2,500 sq ft.
What's the weather doing this month?
Does the burner also heat your hot water?
Many oil homes run hot water off the boiler or an oil-fired tank. That's a steady half to one gallon a day whatever the weather.
What you pay per gallon
From your last delivery ticket. The national residential average was about $5.54 at the end of last season, well above the year before; contract and prebuy prices differ.
Order a refill in about
12 days
120 gallons (half of 240 usable) at 4.9 a day; quarter tank around Oct 13.
Why a quarter tank, and why 275 means 240
Suppliers ask you to order at a quarter tank because a winter delivery takes two to five business days and a cold week can burn through the last quarter faster than the truck arrives; below an eighth, sediment from the bottom of an older tank gets into the fuel line. And the tank is never really full: a 275 holds about 240 gallons, because every tank keeps room for air and for the debris that settles, so "half" on the gauge is about 120 gallons, not 137.
What moves the number
The burner is nearly all of it, and the weather sets the burner: a cold snap burns close to half again what a typical winter month does, a mild month barely half. Hot water off the boiler is a steady half to one gallon a day regardless. If your gauge drops faster than this, the usual reasons are an old burner or an oversized nozzle, a thermostat held high, or heating rooms nobody uses; if it drops much faster, have the supplier check the tank and lines for a leak.
Burn is a supplier's per-square-foot rate at your weather card's temperature, plus a published allowance for oil-fired hot water. A full 275 holds about 240 gallons; the reorder mark is a quarter tank. Actual use depends on the burner, insulation and thermostat. Price defaults to the last EIA national average. 2026 figures.
💡About this calculator▼
Heating oil hides two facts from you. The tank is never as full as the gauge says, because a 275-gallon tank is filled to about 240 to leave room for air and the sediment that settles at the bottom. And the burn rate swings more with the weather than with anything you do: the same house that sips two gallons on a mild day drinks six or seven in a cold snap.
This turns the gauge into dates. Enter the tank, the fraction the float shows, your heated square footage, and the kind of month it is, and the calculator uses supplier burn rates per square foot by outdoor temperature to say how many gallons a day you're using, when the tank reaches a quarter, and when it would run dry.
Order at a quarter tank. That is the rule every supplier gives, because winter deliveries take two to five business days and every truck is booked in the same cold snap that drains every tank. Below an eighth, older tanks start feeding sediment into the fuel line. So the headline here is not days until empty; it is days until you should already have called.
Start with what's actually in the tank. A float gauge reads fractions of the tank, but a full tank isn't the rated size: suppliers explain that every tank keeps room for air and settled debris, so a 275 holds about 240 gallons and reads half at about 120. The calculator applies that 240-of-275 fill to the tank size you pick and multiplies by the gauge fraction.
Then how fast it's leaving. A heating oil supplier publishes burn per 1,000 square feet by outdoor temperature: about 0.87 gallons a day at 50°F, 1.40 at 40°F, 2.07 at 30°F, 2.67 at 20°F, and 3.27 at 10°F. The calculator scales that by your square footage and picks the temperature from the weather card, interpolating between table rows: a mild month around 45°F, a typical winter month around 30°F, a cold snap around 15°F. Other suppliers' figures for a typical home bracket the same range, from a couple of gallons a day in mild weather to seven or more in hard cold.
Add hot water if the burner makes it. Many oil homes heat water off the boiler or an oil-fired tank, and suppliers put that at half to one gallon a day whatever the weather. The calculator adds three-quarters of a gallon when you say yes.
Turn gallons into dates. Gallons in the tank divided by gallons a day is days until empty. The quarter-tank reorder mark is a quarter of the usable fill, so days until you should order is the gallons above that mark divided by the daily rate, and that is the headline. Daily rate times 30 times your price is the month.
📐How it's calculated▼
Gallons in the tank = tank size × (240 ÷ 275) × gauge fraction. A 275 reading half holds 275 × 0.873 × 0.5 = 120 gallons; full is 240.
Burn per day = (square feet ÷ 1,000) × the table rate at your weather. For a 2,000-square-foot house in a typical winter month around 30°F: 2 × 2.07 = 4.1 gallons a day for heat. In a cold snap around 15°F the rate interpolates to 2.97, so 5.9 a day; in a mild month around 45°F it is 1.135, so 2.3.
Hot water off the burner adds 0.75 gallons a day, so the typical-month total is 4.9 gallons a day.
Dates. 120 gallons ÷ 4.9 = about 24 days until empty. The quarter-tank mark is 60 gallons, so the 60 gallons above it last 12 days: that is when to order. At $5.54 a gallon the month costs 4.9 × 30 × 5.54 = $814.
Checking the suppliers' own statements. One says a quarter tank on a 2,000-square-foot house lasts about a week at 20°F: 60 gallons ÷ the cold-snap total of 6.7 a day is 9 days, the same order of magnitude. Another says a typical home burns 3 to 6 gallons a day in winter, and the calculator's 4.1 to 5.9 for a 2,000-square-foot house sits inside that.
📎Sources:U.S. Energy Information Administration — Heating Oil and Propane Update (residential heating oil prices),Hart Home Comfort — How Much Heating Oil Will I Use A Day? (burn per 1,000 sq ft by temperature),Bottini Fuel — How Much Oil Can My Heating Oil Tank Hold? (a full 275 holds about 240),Heatable — When Should I Order More Heating Oil? (the quarter-tank rule)
🔍Finding your inputs▼
Tank size: On the tank's plate. Indoor tanks are almost always 275 gallons; 330 and 500 are the larger indoor and outdoor sizes. The calculator applies the real fill, about 12 percent less than the rated size, so you don't have to.
What the float gauge reads: The glass tube on top of the tank. It's coarse, so pick the nearest mark. If the float sticks, which they do, tap the tube; a gauge that hasn't moved in weeks is a stuck float, not a full tank.
Heated square footage: The area the burner heats. Leave out an unheated basement or garage.
What's the weather doing this month: Pick by the month's average temperature. Around 45°F is a mild shoulder month, around 30°F a typical winter month in the oil-heating states, and around 15°F a cold snap or a northern January.
Does the burner also heat your hot water: Yes if you have a tankless coil in the boiler or an oil-fired water heater. That's a steady half to one gallon a day year-round, and it's why oil homes still take deliveries in summer.
What you pay per gallon: From your last delivery ticket. The national residential average was about $5.54 at the end of the 2025–26 season, well above the year before, and prices differ by supplier, contract, and prebuy, so use your own.
⚠️Special situations▼
My gauge has read the same for two weeks. Am I using no oil?
Almost certainly the float is stuck, which is common on older gauges. Tap the glass; if the float drops, that's your real reading. A stuck gauge is how people run out with a tank that "looked half full," so if it sticks more than once, have the supplier replace the gauge or use a dipstick: the tank charts suppliers publish convert inches of oil to gallons for each tank size. In the meantime, use the calculator's days-until-empty from your last known reading and order on the calendar rather than the gauge.
I ran out of oil. Can I just get a delivery and restart the burner?
Usually not without a technician. When the tank runs dry the burner pulls air into the fuel line, and it won't light again until the line is bled and the pump primed; on older tanks the last gallons also carry sediment that clogs the filter and nozzle. Most suppliers will prime the burner as part of an emergency delivery, for a fee, and it may take a day in a cold snap. That, not the gas itself, is why the quarter-tank rule exists.
My burn is well above what the calculator shows
Work through it in order. The weather card first, since a month with a real cold snap belongs on the cold card even in November. Then the burner: a nozzle one size too big, an old inefficient unit, or a boiler that keeps a tankless coil hot all day burns more than the averages assume. Then the thermostat and the area heated, since a house held at 72 with a heated basement is not the ordinary house the supplier figures describe. If none of that explains it and the tank drops faster than the math over a couple of weeks, have the tank and lines checked for a leak; a smell of oil near the tank makes that call urgent.
Should I buy a bigger tank so I order less often?
A 500-gallon tank holds about 436 gallons usable, so a cold-snap house burning seven gallons a day gets two months instead of one from a fill, and you can buy more when prices are low. The trade-offs are the tank's cost, the space, and, for outdoor tanks, gelling in extreme cold unless the oil is treated. Before sizing up, ask the supplier about automatic delivery: they track degree days and fill before you get low, which solves the ordering problem without a new tank.
❓Common questions▼
How long will a 275-gallon oil tank last in winter?
A full 275 holds about 240 gallons. A 2,000-square-foot home with an oil burner and oil-heated hot water uses about 4.9 gallons a day in a typical winter month, so the tank lasts about 49 days from full, and you would order at the quarter mark after about 37 days. In a cold snap the same house burns closer to seven gallons a day and the tank lasts about five weeks; in a mild month, three gallons a day and well over two months. Suppliers put a typical home at three to six gallons a day in winter.
How much heating oil does a house use per day?
It depends on the size of the house and the outdoor temperature more than anything else. Supplier figures put burn at about 0.87 gallons a day per 1,000 square feet at 50°F, rising to about 2.1 at 30°F and 2.7 at 20°F, so a 2,000-square-foot house runs from under two gallons a day in a mild month to five or more in hard cold. Hot water off the burner adds a steady half to one gallon a day. Other suppliers quote a typical home at three to six gallons a day in winter, which lands in the same range.
Why does a full 275-gallon tank only hold 240 gallons?
Because every oil tank keeps room at the top for air and expansion and, over the years, a layer of sediment at the bottom that the pickup tube sits above. Suppliers fill a 275 to about 240 gallons, and the gauge reads fractions of the tank, so half on the float is about 120 gallons rather than 137. The calculator applies that fill to every tank size, so the gallons it works from are the ones you can actually burn.
When should I order heating oil?
At a quarter tank. Suppliers use that mark because a winter delivery takes two to five business days and a cold week can burn through the last quarter faster than the truck arrives; for a 2,000-square-foot house, a quarter tank is about a week of oil at 20°F. Below an eighth, older tanks start pulling sediment into the fuel line, and an empty tank means the burner has to be bled and primed before it will light again. The calculator's headline is the days until you reach a quarter so you can put the order on the calendar.
How much does heating oil cost per month?
Multiply your daily gallons by 30 and by your price per gallon. At the national average of about $5.54 a gallon, a 2,000-square-foot house with oil heat and oil hot water in a typical winter month burns about 4.9 gallons a day, roughly $814 a month; a cold snap pushes that past $1,100 and a mild month brings it under $500. That average was unusually high at the end of the 2025–26 season, and contract and prebuy prices differ, so enter the number from your last delivery ticket.
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