Heating oil tank calculator

Turning an oil tank level into gallons

The number on a dipstick is a depth, not a quantity. Leave the depth box blank and the calculator returns the tank's full capacity; type the wet-line inches in and you get the gallons sitting in the tank at that level, alongside what full would be.

• Level is measured from the bottom of the tank up, so always let the stick touch bottom before you read it.
• Gallons per inch is not constant. An oval or round tank holds far more per inch through its middle than near the top and bottom curves, so level and percentage full are not the same number.
• A float gauge reads level too, but through a linkage that can stick. If the gauge and a stick reading disagree, believe the stick. See reading an oil tank gauge.
• For a standard tank you do not need to measure anything: the printed tank charts already list every level in inches against gallons.

Measuring tips

• Measure outside dimensions to the nearest half inch. Wall thickness matters less than honest measuring.
• For oval tanks, width is the narrow face dimension and height is the tall one. A standard 275V measures 27″ wide, 44″ tall, 60″ long.
• For buried tanks you usually cannot measure the shell. Use the standard underground charts instead, or your installation records.
• For a buried fiberglass ball, pick the ball option and enter the diameter: about 50 inches for the 285, 62 for the 550, 76 for the 1000. Full charts on the fiberglass ball page.
• The result assumes a clean, uniform shell with flat ends. Factory steel ovals have dished heads that hold about 2 percent more, which our standard charts include; dents, baffles, and sludge subtract a little.

Standard tank capacities and gallons per inch

If your tank is one of the standard sizes there is nothing to measure: the figures below are the same ones the charts are built from. For the full inch by inch conversion, open the chart for your tank.