Bolt Proof Load Calculator
Proof load and recommended preload for metric property classes.
Class 8.8 ≈ 580 MPa proof stress: an M12 proofs at 49 kN. Tighten INTO the proof zone deliberately — a fully preloaded bolt barely feels fatigue, a loose one dies of it.
Formula
Bolt Proof Load Calculator is a free bolt proof load for design engineers, metallurgists and QA inspectors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Bolt Proof Load Calculator
Proof load and recommended preload for metric property classes. The calculation implements F_proof = S_p·A_s; preload ≈ 75% proof (reused) / 90% (permanent) (ISO 898-1; VDI 2230 preload guidance). Class 8.8 ≈ 580 MPa proof stress: an M12 proofs at 49 kN. Tighten INTO the proof zone deliberately — a fully preloaded bolt barely feels fatigue, a loose one dies of it.
How to use Bolt Proof Load Calculator
- 1Enter Stress area A_s in mm² (M8: 36.6 · M10: 58 · M12: 84.3 · M16: 157 · M20: 245).
- 2Enter Property class (4.6 / 5.8 / 8.8 / 10.9 / 12.9).
- 3Read Proof load, Recommended preload (75%) instantly — no submit button needed.
- 4Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Bolt Proof Load Calculator?
- ✓Implements the standard formula — F_proof = S_p·A_s; preload ≈ 75% proof (reused) / 90% (permanent)
- ✓Reference cited on-page: ISO 898-1; VDI 2230 preload guidance
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Bolt Proof Load Calculator use?+
It computes F_proof = S_p·A_s; preload ≈ 75% proof (reused) / 90% (permanent), per ISO 898-1; VDI 2230 preload guidance. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Class 8.8 ≈ 580 MPa proof stress: an M12 proofs at 49 kN. Tighten INTO the proof zone deliberately — a fully preloaded bolt barely feels fatigue, a loose one dies of it.
Where do the material property defaults come from?+
Defaults are standard handbook values (ASM, manufacturer datasheets, the cited standard). Always substitute certified values from your material's test certificate for critical work.
Is the Bolt Proof Load Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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