Tank Volume Calculator
Capacity in gallons and liters for any tank shape (dimensions in inches)
Tank Capacity
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This tank volume calculator finds the capacity of cylindrical, rectangular, and oval tanks. Enter all dimensions in inches. For a cylinder, use diameter and length; for a box or oval tank, fill in all three dimensions. Results show US gallons, liters, and cubic feet.
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Frequently Asked Questions
How do I calculate tank volume?
For a cylindrical tank, volume = π × radius² × length. For a rectangular tank, volume = length × width × height. Divide cubic inches by 231 to get US gallons, or multiply by 0.0163871 to get liters.
How many gallons is a cubic foot?
One cubic foot equals about 7.48 US gallons. One cubic inch equals 1/231 of a gallon, since a US gallon is defined as exactly 231 cubic inches.
What is the difference between US and Imperial gallons?
A US gallon is 231 cubic inches (3.785 liters). An Imperial (UK) gallon is larger — about 277 cubic inches (4.546 liters). This calculator shows US gallons in the main result and Imperial in the breakdown.
How do I find the volume of a horizontal cylinder tank?
For a completely full horizontal cylinder, use the same formula as a vertical one: π × radius² × length. Partial-fill volume of a horizontal tank requires a more complex "circular segment" formula based on the fill depth.
Does tank wall thickness matter?
For capacity, use the internal dimensions. If you only have external measurements, subtract twice the wall thickness from each dimension to get the true holding capacity.