Tank Volume Calculator
Find the capacity and filled volume of vertical, horizontal and rectangular tanks in litres and gallons.
About the Tank Volume Calculator
Choose the tank shape and enter its internal dimensions and the liquid depth. The calculator gives the liquid volume, the full capacity in litres and US gallons, and how full the tank is.
A vertical cylinder holds π r² × height. A horizontal cylinder's filled volume isn't proportional to depth, because the tank is narrower near the top and bottom. 1 m³ = 1,000 litres = 264.17 US gallons.
The formula
Horizontal fill = L × [r² cos⁻¹((r − h) ÷ r) − (r − h)√(2rh − h²)]
Worked example
A horizontal tank 150 cm across and 3 m long, liquid 50 cm deep
- Capacity: π × 0.75² × 3 = 5.30 m³ = 5,301 L
- Liquid: 1,547 L
- Only 29.2% full, although the depth is a third of the diameter
Questions people ask
Why isn't half the depth half the volume?
It is at exactly half for a horizontal cylinder, but not at other depths because the width changes.
Measured outside or inside?
Use internal dimensions.
How do I measure depth?
A dipstick through the top opening; read the wet mark against a tape.