Bolt Torque Calculator
Tightening torque from a target clamp load, or clamp load from a torque.
What is Bolt Torque?
A bolt works by being stretched: the tension left in it after tightening (its clamp load) presses the joint together, and the torque you apply is only the crude way of producing that tension. The short-form relation T = K · d · F bundles the thread friction, the under-head friction and the helix angle into one empirical factor K, which is why the same nominal bolt can need very different torque with and without a drop of oil.
How it works
Torque is K × diameter × clamp load, with the diameter in metres and the force in newtons. Solving the same relation the other way gives the tension a torque actually produces. The page offers the common nut factors — 0.20 dry plain steel, 0.18 zinc-plated dry, 0.16 lightly oiled, 0.14 lubricated — and lets K be typed in for anything else, and it shows the answer in both N·m and lb·ft because torque wrenches come both ways.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.