Fitting reference
Measure the thread, count the threads, check parallel against tapered, look at the seat. 110 sizes across 10 standards - JIC, ORFS, SAE O-ring boss, SAE 45, NPT, BSPP, BSPT, metric DIN 2353, JIS and Komatsu - with every dimension checked against two independent published sources.
Most looked up
By family
The expensive mistakes
A wrong fitting that will not thread on is an inconvenience. A wrong fitting that threads on and holds pressure on the bench is a callback. These pages separate the two.
Why trust the numbers
Every one of the 110 sizes was cross-checked against at least two independent publishers, and three of the sources are the standards themselves, read directly: ASME B1.20.1 Table 1, ISO 228-1 Table 1 and ISO 7-1 Table 1. A figure only one publisher carries is not here.
Three charts give three different diameters for a BSPT male, because a tapered thread measures differently depending on where the caliper sits. All three are printed on the size page along with the reason. Two catalogues disagree about NPTF pressure at 1/4 and 3/8, so neither of those sizes carries a number at all.
61 of the 110 sizes carry a published working pressure, and every one prints the exact conditions it applies under - material, design factor, straight or adjustable stud. The other 49 carry none, because no two independent sources rate them under conditions they both state. There is no generic typical figure anywhere on this site.
13 figures that exist somewhere in print could only be corroborated once, so they are absent from the database and listed instead. Read the full register, the disagreements and the gaps.
Guides
Every size page, every comparison, every guide, the identify flow and every published pressure rating with the conditions it applies under are free, and always will be. Nothing safety-relevant is ever behind a paywall. There is no account and no sign-in, and nothing you measure or list leaves your browser.
FittingKey is a reference aid for identification and ordering, not a substitute for the manufacturer specification. It is independent, and is not affiliated with, endorsed by or connected to SAE International, ISO, ASME, DIN, JIS or any fitting manufacturer.