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Well Pressure Tank Sizing Calculator

Get a recommended pressure tank size based on your pump's flow rate and a minimum pump cycle time.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-27 · v1.1.0

Market
Imperial · sales tax

Recommended tank size

30.3 gal

Check your inputs

Actual drawdown fraction varies by tank precharge pressure and your specific pressure switch cut-in/cut-out settings — check your tank manufacturer's drawdown chart for a precise figure.

Required drawdown
10 gal

Running these inputs gives 30.3 gal as the recommended tank size. Required drawdown carries the most weight in this calculation, at 10 gal. Expect some drift against the real job; the calculation is solid but conditions on site are not. Currently reading for United States — pick a different market above and the figures re-cast accordingly.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • Required drawdown = pump flow rate × minimum recommended cycle time (minutes); recommended tank size = required drawdown ÷ typical drawdown fraction (~33% for a standard captive-air tank)

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why does short-cycling matter?
A pump that starts and stops too frequently (short-cycling) wears out its motor and pressure switch contacts much faster than one that runs for a reasonable, steady duration each cycle — an undersized pressure tank is a common cause of short-cycling.
What is 'drawdown' exactly?
Drawdown is the volume of water a pressure tank can deliver between the pump's cut-in and cut-out pressure settings — it's always less than the tank's total volume, since some volume remains as a compressed air cushion even at cut-out pressure.
Does a bigger tank always mean better performance?
A larger tank generally means longer pump run times and less frequent cycling, which is good for pump longevity — but it also costs more and takes up more space, so this estimates a reasonable minimum, not a maximum.