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Bolt Tensile Stress Area Calculator: Load to MPa and psi
Pick a thread or enter diameter and pitch. The tool gives the tensile stress area, then converts a test load on that bolt or threaded rod to stress, or a stress to load.
Thread
Load to stress
Stress to load
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Metric coarse stress areas
| Thread | As |
|---|
| M5 × 0.8 | 14.2 mm² |
| M6 × 1 | 20.1 mm² |
| M8 × 1.25 | 36.6 mm² |
| M10 × 1.5 | 58.0 mm² |
| M12 × 1.75 | 84.3 mm² |
| M14 × 2 | 115.4 mm² |
| M16 × 2 | 156.7 mm² |
| M20 × 2.5 | 244.8 mm² |
| M24 × 3 | 352.5 mm² |
| M30 × 3.5 | 560.6 mm² |
| M36 × 4 | 816.7 mm² |
Inch (UNC) stress areas
| Thread | As | As |
|---|
| #10-24 UNC | 0.0175 in² | 11.3 mm² |
| 1/4-20 UNC | 0.0318 in² | 20.5 mm² |
| 5/16-18 UNC | 0.0524 in² | 33.8 mm² |
| 3/8-16 UNC | 0.0775 in² | 50.0 mm² |
| 7/16-14 UNC | 0.1063 in² | 68.6 mm² |
| 1/2-13 UNC | 0.1419 in² | 91.5 mm² |
| 5/8-11 UNC | 0.2260 in² | 145.8 mm² |
| 3/4-10 UNC | 0.3345 in² | 215.8 mm² |
| 7/8-9 UNC | 0.4617 in² | 297.9 mm² |
| 1-8 UNC | 0.6057 in² | 390.8 mm² |
The formulas
Metric: As = π/4 × (d − 0.9382 × P)², with d the nominal diameter and P the pitch in mm. Inch: As = π/4 × (D − 0.9743 / n)², with D in inches and n threads per inch. Stress = load / As. Unit factors are exact: 1 lbf = 4.4482216152605 N, 1 in = 25.4 mm, so 1 MPa = 145.0377 psi. The tables are rounded to 0.1 mm² and 0.0001 in²; the calculator shows more digits.
The stress area is a nominal value for the threaded part. It does not include the bolt's strength class, the anchor's capacity in concrete or any safety factor, and the tool does not set a proof load or a limit; those come from your spec or the fastener standard it names. Compare a computed area with that standard's table if your spec gives one. To size the test load first, use the sample size and proof load planner; to convert units, the force unit converter; to record the test, the free pull-test record sheet.
Record the results in the full report workbook
The Fastener & Anchor Pull-Test Report Templates pack has a 40-row proof-test report with automatic PASS/FAIL, ultimate-load statistics, a calibration log, a unit converter, a printable procedure checklist and a standards index. $49 one-time, from Quality Tester Solutions LLC, the company behind Force-Test pull testers.