Water Tank Capacity Calculator
Choose the tank shape and enter the internal dimensions. Use the water depth, not the outer height.
Your result will appear here after you press Calculate.
How this calculator works
Rectangular = length × width × water depth
Cylindrical (upright) = π × (diameter ÷ 2)² × water depth
Conical frustum = (π × h ÷ 3) × (R² + R·r + r²)
Litres = m³ × 1000; the fill percentage scales the result.
Assumptions and limits
- Use internal dimensions. Wall thickness is not deducted automatically.
- The frustum option assumes the bottom and top are circular and the tank widens or narrows in a straight line.
This tool gives an approximate estimate from the values you enter. It is not a substitute for professional engineering design, site inspection, official quotations or applicable building regulations. See the calculator disclaimer.