Bolt Tensile Stress Area Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the bolt's nominal diameter and thread pitch (mm).
- Optionally add the proof strength to get the proof load.
- Read the tensile stress area and proof load.
How it works
The Bolt Tensile Stress Area Calculator finds the area a metric bolt uses to carry tension — smaller than the shank because the load passes through the threads.
Aₜ = (π/4)(d − 0.9382·p)² from ISO 898, where d is the nominal diameter and p the pitch. The proof load is Aₜ × the proof strength (e.g. 830 MPa for class 8.8).
Worked example
M10 × 1.5, class 8.8. Aₜ = (π/4)(10 − 0.9382×1.5)² ≈ 58.0 mm²; proof load = 58.0 × 830 ÷ 1000 ≈ 48.1 kN.
Frequently asked questions
Why not just use the shank area?
A bolt fails through its threads, where the effective area is smaller. The tensile stress area accounts for the thread profile, so tensile strength is based on it, not the plain shank.
Can I use these results for final design?
No. These calculators are for first-pass sizing, checking and learning. They assume ideal supports, static loads and elastic behaviour, and they don't apply load factors, member capacity, buckling or connection checks. Always verify against the relevant design code (e.g. AS 4100, AS 1170, Eurocode) and have a qualified engineer sign off structural work.
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Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.