Estimate pressure tank size for a well pump or water pressure system. Calculate recommended tank capacity, drawdown gallons, pump run time, pump flow rate, cut-in pressure, cut-out pressure, precharge pressure, and usable water storage.
Recommended tank size:
The calculator estimates required drawdown from pump flow rate and desired run time, then estimates total tank size from the pressure range and precharge setting.
Drawdown needed:
The calculator multiplies pump GPM by desired run time to estimate how many gallons should be available before the pump restarts.
Pump run time:
If you enter a known tank size, the calculator estimates usable drawdown and expected pump run time.
Usable water:
The calculator estimates usable storage between cut-in and cut-out pressure.
A pressure tank size calculator helps estimate how much tank capacity is needed to reduce short cycling and give the pump a reasonable run time.
It can help compare pump flow rate, drawdown gallons, total tank size, pressure switch settings, precharge pressure, daily cycles, and usable water storage.
Your result shows an estimated pressure tank size and drawdown requirement. This is a planning estimate only. Actual drawdown depends on the tank model, bladder design, precharge, cut-in pressure, cut-out pressure, pump curve, and manufacturer data.
Estimate the drawdown needed from pump flow rate and desired run time, then choose a pressure tank that provides at least that much drawdown at your pressure switch setting.
Drawdown is the amount of usable water stored between the pump cut-out pressure and cut-in pressure.
For many bladder tanks, precharge is commonly set about 2 PSI below the pressure switch cut-in setting, but always check the tank manufacturer’s instructions.
No. This calculator gives a planning estimate. Final tank sizing should use the manufacturer’s drawdown chart and account for pump flow, pressure switch settings, demand, and system design.