Building & DIY

Tank Volume Calculator (Four Shapes)

Find the capacity of a tank in four common shapes: rectangular, vertical cylinder, horizontal cylinder, and oval. Enter the dimensions and you get US gallons, UK gallons, liters, and more.

How to use
  1. Pick the tank shape.
  2. Enter the dimensions in feet, inches, metres, or centimetres.
  3. Switch shapes to compare capacities.
Quick fill
Capacity

enter the tank dimensions

Litres
UK gallons
Cubic feet
Cubic metres
Estimates only, allow for waste and confirm against local building codes and supplier specs.
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How it's calculated

cylinder V = π × (D÷2)² × H; gallons = litres ÷ 3.785

V = volume, D = diameter, H = height or length, π ≈ 3.14159. Rectangular V = L×W×H; oval V = π×(W÷2)×(H÷2)×L. 1000 L per m³; ÷3.785 converts litres to US gallons.

Common questions

What is an oval tank?

It is a horizontal cylinder with an elliptical cross-section, common for fuel and water storage. Enter its width, height, and length.

Does it give both US and UK gallons?

Yes. The US gallon is about 20 percent smaller than the UK imperial gallon, so the calculator shows both.