Water Tank Calculator — Calculate Tank Capacity in Litres

Tank Shape

Diameter (m) Enter a valid dimension.

Height (m) Enter a valid height.

Tank Capacity

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How to Use This Tool

Select your tank shape — cylindrical or rectangular.
Enter the required dimensions in metres.
Click Calculate Capacity to get the volume in litres.

Water Tank Volume Formulas

Cylindrical Tank

Volume (litres) = π × (Diameter ÷ 2)² × Height × 1,000

Rectangular Tank

Volume (litres) = Length × Width × Height × 1,000

Both formulas calculate volume in cubic metres first, then convert to litres by multiplying by 1,000 (since 1 m³ = 1,000 litres).

Practical Uses

Sizing a new water storage tank for household or building requirements
Estimating existing tank capacity when planning water usage or backup supply
Construction and plumbing planning for water storage systems

A Practical Tip

Always measure internal dimensions (not external, which would include wall thickness) for an accurate usable capacity figure, and consider leaving a small buffer below the maximum fill line to avoid overflow.

Frequently Asked Questions

Should I measure internal or external tank dimensions?

Use internal dimensions for an accurate usable capacity — external dimensions would overstate capacity by including the tank wall thickness.

Why multiply by 1,000 to get litres?

Volume calculated in cubic metres needs to be converted to litres, and since 1 cubic metre equals exactly 1,000 litres, multiplying by 1,000 gives the capacity in the more commonly used litre unit.

This calculator is provided for general informational and estimation purposes only. Results should not be treated as professional financial, tax, legal, medical, or engineering advice. Always verify critical calculations with a qualified professional or official source before making decisions.