Capacity • Current level • Fill time

Know how much water your tank holds—and how long it will take to fill.

For homeowners, plumbers, installers and facility teams. Enter internal measurements for a transparent geometric estimate.

Step 1

Enter tank details

Tank shape

Rectangular Vertical cylinder

Internal length

Internal width

Internal height

Current water level Optional

Select its unit independently from tank height.

Inlet flow rate Optional

Flow unit

Step 2

Enter your tank measurements to calculate capacity.

Flow rate is optional.

Don’t know your flow rate?

Time how long your inlet takes to fill a bucket. Keep the tap or pump setting unchanged.

Measured flow—

How the calculation works

Rectangular: length × width × water height.

Cylindrical: π × radius² × water height.

Fill time: remaining litres ÷ litres per minute.

All measurements are converted to metres internally; 1 m³ = 1,000 L.

Limits and safety

Measure inside the tank; external dimensions overstate capacity.
Irregular shapes, rounded corners, fittings, dead storage and freeboard reduce usable capacity.
Flow can change with pressure and pump head; measure under normal conditions.
Water is treated as approximately 1 kg/L. This tool does not verify structural support.

Formula sources

Tank-volume formulas follow published public-health guidance. Unit conversions use exact international definitions where available.

Sources reviewed 26 August 2026.