Water Tank Capacity & Fill-Time Calculator

Use this calculator to estimate a rectangular or cylindrical water tank's total capacity, current water volume, remaining litres and fill time. Choose the tank shape and enter measurements in the units requested by the tool.

Measure before entering values

For a rectangular tank, measure its inside length, width and height. For a cylindrical tank, check whether the tool asks for diameter or radius and measure the internal height. Enter the current water depth separately. Wall thickness and unusable space can make the practical capacity lower than the outside dimensions suggest.

Estimate fill time

Use a measured inlet flow rate when possible. Flow can change with supply pressure, pipe restriction, pump condition and voltage, so the displayed fill time is an estimate. If the tank is already partly full, use the remaining volume rather than total capacity.

Check the result

Confirm that all units are correct before acting on the output. Do not use this screen alone to size structural supports, overflow pipes or a pump. For installation decisions, verify site measurements and safety requirements with a qualified professional.

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.

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Use this calculator to estimate a rectangular or cylindrical water tank's total capacity, current water volume, remaining litres and fill time. Choose the tank shape and enter measurements in the units requested by the tool.

Measure before entering values

For a rectangular tank, measure its inside length, width and height. For a cylindrical tank, check whether the tool asks for diameter or radius and measure the internal height. Enter the current water depth separately. Wall thickness and unusable space can make the practical capacity lower than the outside dimensions suggest.

Estimate fill time

Use a measured inlet flow rate when possible. Flow can change with supply pressure, pipe restriction, pump condition and voltage, so the displayed fill time is an estimate. If the tank is already partly full, use the remaining volume rather than total capacity.

Check the result

Confirm that all units are correct before acting on the output. Do not use this screen alone to size structural supports, overflow pipes or a pump. For installation decisions, verify site measurements and safety requirements with a qualified professional.