Bolt Length Calculator for HR Bolts and HR Countersunk Bolts (EN 14399-3/7)

Andrews Fasteners Bolt Length Calculator for BS EN 14399 High-strength structural bolting assemblies for preloading (HR)

HR Bolt to EN 14399-3:2015 / HR Countersunk bolt EN 14399-7:2018

This calculator is for guidance only and is used for calculating the minimum recommended bolt length based on maximum allowed thickness of the assembly components and the steelwork.

This information is provided in good faith and is for your guidance only. Andrews Fasteners Limited can not accept any liability for actions taken by third parties based on this information.

Bolt Length Calculator

Steelwork thickness mm
Bolt length (calculated):
Bolt length (ref.):
Version: JS/1.02.210721.14399.2015

Whilst the information is provided in good faith, Andrews Fasteners Ltd are not under any responsibility or liability in respect of errors or information that was found to be incorrect or for any reliance the user may place on it.

Nut used in calculation refer to EN 14399-3 / EN 14399-7 (HR Nut)

Washer refer to EN 14399-5 (4) (washer under the nut) or EN 14399-6 (4) ( chamfered washer under bolt head) - Hardness 300-370 HV

NFW (2) refers to Nut Face Washer EN 14399-9 (Hard washer) - Hardness 38-45 HRC

BFW (2) refers to Bolt Face Washer EN 14399-9 (Hard washer) - Hardness 38-45 HRC

DTI (1) refers to Direct Tension Indicators Washer EN 14399-9 - Hardness max. 380 HV - maximum height including protrusions (3).

Steelwork refers to the thickness of the steelwork that needs to be tightened including minimum 1 thread above the face of the unloaded nut on the assembly. If additional plates are required - i.e. to cover oversized holes - include thickness into total thickness of the steelwork.

Don’t know which components to use on HR assembly?

For calculation of thread lengths refer to:

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