Bolt Elongation Calculator

Inputs

Preload (F)

Clamp force / tensile load in the bolt.

Stressed length (L)

Effective elastic length under tension. Often grip length plus a portion of the engaged threads and head/nut compliance.

Nominal diameter (d)

Nominal bolt diameter.

Thread pitch (P)

Thread pitch, used for tensile stress area when the threaded section controls.

Area basis

Use tensile stress area for threaded stretch, or shank area for an unthreaded reduced model.

Young’s modulus (E)

Steel is about 200 GPa; titanium about 110 GPa; aluminum about 69 GPa.

GPa

Default result

Elastic elongation(δ)

0.1078mm

Pass

elastic range for most steel bolts

Also computed

Bolt stress(σ)431.1MPa

σ = F/A

Elastic strain(ε)0.002156

ε = σ/E

Area used(A)57.99mm²

tensile stress area

Method notes 3 notes

Elastic stretch δ = F·L/(A·E). The model assumes the bolt remains elastic and the load is axial.
The effective stressed length is not always just the grip: head, nut and engaged-thread compliance can add elastic length.
Use the bolt proof/yield strength to judge whether the stress is acceptable for the joint.