Lug Nut Torque & Clamp Load Calculator
What a torque figure actually clamps — where about ninety per cent of it goes into friction, and the same 110 Nm spans two and a half times the clamp load.
The nut factor is an empirical bundle rather than a measured constant — it covers thread friction, the friction under the seat, the finish and how many times the joint has been done up. The usual figures are 0.2 dry and 0.15 lubricated, and a real joint can sit either side of those. Always use the torque your manufacturer specifies. Nothing is uploaded.
About ninety per cent of the torque never reaches the joint
Torque is a proxy. What holds a wheel on is clamp load — the tension stretched into the stud — and torque only reaches it through friction it has to overcome first. Turning a thread one revolution advances it by its pitch, so the share that becomes tension is P/(2π) against the K·D the whole torque is spread over. On an M12×1.5 at a dry nut factor of 0.2 that is 9.95% — leaving 90.05% going into friction and never reaching the joint at all.
| Stud | Becomes tension | Lost to friction |
|---|---|---|
| M12×1.5 dry | 9.95% | 90.05% |
| M12×1.5 lubricated | 13.26% | 86.74% |
| M14×1.5 dry | 8.53% | 91.47% |
| M12×1.25 dry | 8.29% | 91.71% |
A finer pitch passes less on, and a fatter stud less still — but every one of them is mostly friction. Which is why the state of the thread matters far more than the number on the wrench.
So the same 110 Nm spans two and a half times the clamp load
Clamp load is T/(K·D), so the nut factor is the whole game. At an identical 110 Nm a rusty thread gives 30.6 kN and anti-seize gives 76.4 kN — the same wrench setting, and 2.5 times the load. Oil alone adds 33% over dry, and anti-seize adds 67%. That is the whole reason a specification says clean and dry, and the whole reason anti-seize on wheel studs will over-stretch them at the book figure.
| Thread condition | K | Clamp at 110 Nm | Against dry |
|---|---|---|---|
| Rusty or galled | 0.3 | 30.6 kN | 0.667× |
| Plain steel, clean and dry | 0.2 | 45.8 kN | 1.000× |
| Zinc plated | 0.18 | 50.9 kN | 1.111× |
| Lightly oiled | 0.15 | 61.1 kN | 1.333× |
| Anti-seize | 0.12 | 76.4 kN | 1.667× |
For scale, 110 Nm — about 81 lb-ft — puts roughly 46 kN into a dry M12 stud, which is over 4.7 tonnes of force. Per stud.
| Torque | In lb-ft | Clamp, dry | Clamp, lubricated |
|---|---|---|---|
| 80 Nm | 59.0 | 33.3 kN | 44.4 kN |
| 100 Nm | 73.8 | 41.7 kN | 55.6 kN |
| 110 Nm | 81.1 | 45.8 kN | 61.1 kN |
| 120 Nm | 88.5 | 50.0 kN | 66.7 kN |
| 140 Nm | 103.3 | 58.3 kN | 77.8 kN |
| 160 Nm | 118.0 | 66.7 kN | 88.9 kN |
How to use
- Enter the torque your manufacturer specifies.
- Enter the stud diameter and thread pitch.
- Enter a nut factor for the thread condition.
- Read the clamp load, and what lubricant would do to it.
Frequently asked questions
How much of the torque becomes clamp load?
Under a tenth. On an M12x1.5 stud at a dry nut factor of 0.2, 9.95% of the torque becomes tension and 90.05% is spent overcoming friction before it ever reaches the joint.
Why does that not add up to the numbers on the wrench?
Because torque is a proxy. Turning a thread one revolution advances it by its pitch, so the share doing useful work is the pitch over two pi against the K times D the whole torque is spread over.
What does anti-seize do to a wheel stud?
It raises the clamp load by about two thirds at the same torque, because it drops the nut factor from roughly 0.2 to 0.12. At the book figure that will over-stretch the stud, which is why specs say clean and dry.
How much does a bit of oil matter?
A third more clamp load for the same wrench setting. That is not a rounding error — it is the difference between a correctly tightened joint and a yielded one, from something as small as a wet thread.
What about a rusty thread?
It goes the other way, giving about a third LESS clamp than intended. So the same 110 Nm spans 30.6 kN on a rusty stud to 76.4 kN with anti-seize: two and a half times the load, from one number on the wrench.
How much force is holding my wheel on?
About 45 kN per stud at 110 Nm dry on an M12 — over four and a half tonnes of clamping force, per stud. The wheel is held by friction between the faces rather than by the studs in shear.
What is the nut factor exactly?
An empirical bundle rather than a measured constant. It covers thread friction, the friction under the seat, the finish, and how many times the joint has been done up. The usual figures are 0.2 dry and 0.15 lubricated.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.