Building & DIY

Bolt Torque Calculator (Metric, ISO 898-1)

Gives the recommended tightening torque for a metric bolt from its diameter and strength grade. You can set the K factor for dry or lubricated threads, which changes the result a lot.

How to use
  1. Pick the bolt diameter and ISO 898-1 grade (such as 8.8 or 10.9).
  2. Choose the lubrication condition to set the K factor.
Estimates only, allow for waste and confirm against local building codes and supplier specs.
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Common questions

Why does lubrication change the torque?

Oil lowers friction, so a lubricated bolt reaches the same clamp load at lower torque. The K factor drops from about 0.20 dry to 0.15 or less lubricated.

What torque for an M10 grade 8.8 bolt?

Roughly 45 to 50 N·m dry, but it depends on the K factor and target clamp load, so check the calculated value.

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