Oil and propane tank calculator
Pick your tank and enter the dip reading to see the gallons left. For propane, switch to the Propane tab and enter the gauge percent. Dated readings further down estimate when the tank runs low.
How the numbers are worked out
- The volume at each depth comes from the shape of the tank's cross-section. An oval-ended tank is a rectangle with a half circle at each end, and the oil at a given depth fills part of that shape. Round tanks lying down use the same circle math. Upright round tanks and boxes fill evenly, so each inch holds the same amount.
- The chart runs to the very top of the tank. Tanks are not filled that far: InspectAPedia notes a 275 gallon tank may be marked "Maximum Fill 247 gallons", and that the fill alarm sounds about 6 in from the top. PickHVAC puts the usual maximum fill for a 275 at 220 to 248 gal.
- A 27 × 44 × 60 in tank works out to 267.9 gal by its shape, a little under the 275 on the label. My guess is that the outside size includes the steel and the rounded seams, and the label is a round number.
- PickHVAC advises pushing the stick straight down in the middle of the tank, because a slanted stick reads high. A tank that leans toward one end will read differently at each end.
- US gallons are 231 cubic inches. Liters are 1,000 cubic centimeters.
Where the preset sizes come from
- 275 and 330 gal oval-ended tanks: InspectAPedia's oil tank size table (44 × 60 × 27 in and 44 × 72 × 27 in).
- Round tanks lying down: the Modern Welding UL-142 brochure (48 × 72 in, about 560 gal; 64 × 72 in, 1,000 gal).
- Roth DWT 275: a retailer listing (28 × 43 × 65 in). The oil sits in a blow-molded inner tank, so the box shape is an approximation.
- Titan EcoSafe tanks: the Kingspan product selector (03/2026) for outside sizes and capacities.
How to use it
- Pick your tank from the list. Standing and lying-down 275 and 330 gallon tanks are separate entries, because the same steel holds a different amount at each inch. If yours is not listed, choose "Other size" and type the width, height and length.
- Dip the tank with a stick, wipe it and read the wet mark. Type that number as the dip reading.
- The tool gives gallons, percent full and room left. The chart under it lists every inch for the same tank.
- For a run-out date, add two or more dips with dates, plus any delivery between them. It divides the oil used by the days passed.
Worked example: a 275 gallon tank in January
The tank is the standing 275 (27 × 44 × 60 in). Its shape works out to 267.9 gal when full. A dip reading of 18 in is 105.9 gal, which is 39.5% full, so about 40%. Suppose the 10% line, 26.8 gal, is where you want a delivery to start. That leaves 79.1 gal of usable oil. At 5 gal a day, a round example figure for a cold winter day, that is 15 days.
Measuring your own rate is better. Say the tank read 30 in on January 2 (190.1 gal) and 20 in on January 16 (119.9 gal), with no delivery between. That is 70.1 gal in 14 days, 5.01 gal a day or 35.1 gal a week. The 119.9 gal in the tank now includes 93.1 gal above the 10% line, so the estimate is 18 more days, around February 3. A cold snap shortens that, so add a new dip every week or so and the date adjusts.
What it does not do
- It does not read a gauge for you. The chart follows the dip stick, not a float gauge.
- It does not know your furnace. The run-out date is the past rate carried forward.
- It does not save your readings on a server. They live in the link you copy.
- The preset sizes are outside dimensions from published tables. A tank with a dent, a slope or a thick wall holds a little less than the chart says, and the double-wall presets are scaled to the label.
Questions
How many gallons are in my oil tank at half full? On a standing 275 the half-full dip is 22 in, which is 134 gal. The quarter tank guide gives the 1/4, 1/2 and 3/4 marks for 275, 330 and 550 gallon tanks.
Why does a 275 gallon tank not hold 275 gallons? The shape works out to 267.9 gal, and delivery trucks stop short of the top. InspectAPedia notes a 275 gallon tank may be marked "Maximum Fill 247 gallons", and PickHVAC puts the usual maximum fill at 220 to 248 gal.
When should I order? Your supplier's lead time decides. The tool counts 10% as empty by default, which is my choice. Change that under the run-out settings.
How do I check the dip stick reading? PickHVAC advises pushing the stick straight down in the middle of the tank, because a slanted stick reads high. A tank that leans toward one end will read differently at each end.
Sources
Tank sizes come from InspectAPedia's oil tank size table and PickHVAC, with the other presets listed under "Where the preset sizes come from" above. The volume math is my own calculation from the tank shape. The 5 gal a day is an example figure; EIA's seasonal averages and the degree-day math are in heating oil use per day.
Guides
- 275 gallon oil tank chart: standing and lying down, every inch, and how to dip.
- 330 gallon oil tank chart: dip stick inches and gauge marks to gallons, standing or lying down.
- 500 gallon oil tank chart: inches to gallons for a 48 in round tank, and how it differs from a 550.
- 550 gallon oil tank chart: a 48 × 72 in tank lying down, with gauge marks and the usual 500 gallon fill.
- 1000 gallon oil tank chart: both common shapes, inch by inch, and the 900 gallon fill.
- How many gallons in a quarter tank of oil: 1/4, 1/2 and 3/4 gauge marks in gallons for 275, 330 and 550 tanks.
- How many gallons per inch in an oil tank: what one inch on the stick is worth at five depths for seven tanks.
- How long will heating oil last: the run-out math with a worked example.
- How long will 100 gallons of heating oil last: days by daily use or burner size.
- Heating oil usage per day: gallons a day at outdoor temperatures from 50 down to 10 °F.
- Heating oil usage per month: a yearly total split into months for four New England cities.
- 1200 litre oil tank chart: bunded plastic tanks in the UK and Ireland, by depth in cm.
- 2500 litre oil tank chart: the big bunded Titan ES2500 and round ESV1300 by depth in cm, with fills a year.
- How long does 1,000 litres of heating oil last: months of kerosene by heating hours, and your own rate from two dips.
- 500 gallon propane tank chart: gauge percent to gallons, and how long a tank lasts.
- 1000 gallon propane tank chart: gallons by gauge percent, days to 20% for a whole house and fills per year.
- 120 gallon propane tank chart: gallons by gauge percent, and how long 96 gal lasts with a water heater, range or fireplace.
- 250 gallon propane tank chart: gallons by gauge percent and deliveries a year.
- What size propane tank do I need: 120 to 1,000 gallon tanks side by side, with fills a year for hot water or a furnace.
- How much propane does a house use per month: gallons by month in four states, mostly November to March.
- How long does a 100 lb propane cylinder last: hours for 20 to 420 lb cylinders from your appliance's Btu rating.
- How long does a 20 lb propane tank last: hours for a grill, a patio heater and a Buddy heater at full and half output.
- Propane tank percentage chart: gauge percent to gallons for 120 to 1,000 gal tanks, side by side.
- How much propane does a furnace use per day: gallons per hour and per day from your furnace's rating and the weather.
- Cost to fill an oil or propane tank: dollars for a delivery by tank size and starting level, at your price.
- Heating fuel cost comparison: oil, propane, gas, electric, heat pump, pellets and wood per million Btu, at your prices.
- Heat pump vs oil heating cost: the electricity price where a heat pump matches oil, by COP and oil price.