NormCalcEngineering tools
Bolted joints

Bolt Preload Calculator

Determine bolt preload from tightening torque, thread geometry, and separate friction conditions.

ISO898
01

Bolt data

02

Results

Set the inputs and start the calculation.

From torque to clamp load

What this calculator does

Tightening torque, thread size, bearing diameter, and friction coefficients estimate assembly preload.

The calculator inverts the same friction model as the torque calculator. It reveals how assumed friction shifts expected preload, but it does not replace measurement.

Typical tasks
  • Estimate preload from assembly torque
  • Study lubricant influence
  • Check plausible under- or over-preload

Related calculators

Torque from target forceDetermine nominal torque for a target preload.Bolt stressCheck estimated preload as bolt stress.
Design notes and follow-up standards

Check before release

01

Avoid false precision

Without tested friction data, actual preload is much less certain than the display suggests.

02

Choose measurement

For critical joints, consider direct or indirect preload measurement or monitored tightening.

03

Embedding loss

Preload immediately after assembly is not automatically the minimum clamp load retained in service.

Useful follow-up standards

01

ISO 16047

Determines actual torque/preload behaviour under defined test conditions.

02

VDI 2230 Part 1

Assesses tightening factor, embedding, and required minimum preload.

03

VDI 2230 Part 2

Extends single-bolt principles to multi-bolt joints.