Fastener Guide / Torque / Calculator
Bolt Torque Calculator
Pick the bolt and how it will be installed. The answer shows every assumption — stress area, proof load, clamp load and K — so a counter person can check it.
Share this exact setup: the page address updates as you change the inputs.
Do not use these values for pretensioned or slip-critical structural joints (ASTM F3125 A325 / A490 under RCSC). Those are installed by turn-of-nut, calibrated wrench, twist-off or DTI methods.
Lubrication changes the answer. Applying a dry value to a lubricated, plated or anti-seized bolt can yield or break it. The manufacturer’s or engineer’s value always governs.
K factor
| Condition | Typical K | Note |
|---|---|---|
| Plain steel, dry, as received | 0.20 | This chart’s dry column |
| Zinc plated, dry | 0.17 – 0.22 | Varies with plating and topcoat; many sealers add lubricity |
| Light machine oil | 0.15 – 0.18 | This chart’s lubricated column uses 0.15 |
| Moly paste or anti-seize | 0.10 – 0.13 | Big drop — a dry value here can yield the bolt |
| Stainless on stainless, dry | 0.25 – 0.35 | Galling risk: use anti-seize and tighten slowly |
Typical ranges only. Actual K depends on finish, lubricant, washer, speed and even the batch — test critical joints.
