Fastener Torque Calculator

Fastener Torque Calculator

How much torque actually achieves your desired bolt clamping force? This calculator applies the standard short-form torque-tension relationship.

Torque = K × Clamp Force × Nominal Diameter

Example

10mm bolt, 15,000 N desired clamp force, K = 0.2 (typical dry steel fastener):

Torque = 0.2 x 15,000 x 0.01 = 30.0 N┬Àm

What the K Factor Represents

The K factor (also called the "nut factor") accounts for friction at both the thread interface and the bearing surface under the bolt head or nut - dry, unlubricated steel fasteners typically use K around 0.2, while lubricated or coated fasteners can have meaningfully different, sometimes significantly lower, K values.

Why Lubrication Condition Matters So Much

Torque specifications always assume a specific lubrication condition, which is exactly why applying a torque spec meant for dry threads to a lubricated bolt can result in significant overtightening - the same applied torque produces much higher actual clamp force under reduced friction, potentially exceeding the bolt's safe elastic limit and risking bolt failure or joint damage.