API 653 Calculators
Live calculators for the API 653 formulas inspectors reach for most — every constant and formula traceable to its clause. Built by TankForge.
For estimating and checking. The inspector of record is responsible for every number that goes into a report. Verify against the current edition of API 653 — this page was checked against API 653, 5th Edition, Addendum 2 (May 2020). Not a substitute for the standard or for engineering judgment.
Shell minimum thickness (t-min) calculator
One-foot-method t-min per shell course — and its inverse, maximum fill height from a measured thickness.
Free · API 653 §4.4.5.1Bottom repair-threshold calculator
Repair every bottom reading at or below X so the next internal interval reaches N years — closed form and per-plate table.
Built by TankForge — API 653 inspection software
The Annex C checklist, tank drawings, UT readings and the finished report, on one iPad, from the tank deck — even with no signal.
Free printable guides to other tank parts are coming — shell, bottom & foundation, nozzles.
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