Fastener Guide / Technical Reference

Torque Calculation Methods

Torque is an indirect way to reach clamp load. The common estimate is T = K x D x F: nut factor times diameter times desired clamp load, with clamp load often set at 75% of proof.

Last reviewed 2026-09-10 · Governing standard: Industry practice; VDI 2230 for engineered joints · reference FG-33242A · Report an error on this sheet

Before you use a torque value: these are starting estimates for general bolting. Do not use them for pretensioned or slip-critical structural joints (ASTM F3125 A325/A490 under RCSC) — those are installed by turn-of-nut, calibrated wrench, twist-off or DTI methods. Lubrication changes the answer: a dry value applied to a lubricated or plated bolt can yield or break it. The manufacturer’s or engineer’s value always governs.

Typical nut factor K (estimates; verify)

ConditionK
Plain steel, dry0.20
Zinc plated, dry0.20
Lubricated / oiled0.15 - 0.18
Anti-seize compound0.12 - 0.16
Hot-dip galvanized, lubricated nutper manufacturer / RCSC

These tables carry the same figures as the printed sheet below.

The printed sheet

Torque Calculation Methods

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Text version of this sheet

Estimating torque · T = K x D x F

What it is

FIELD IDENTIFICATION

Torque is an indirect way to reach clamp load. The common estimate is T = K x D x F: nut factor times

diameter times desired clamp load, with clamp load often set at 75% of proof.

MFG

T=KxDxF

Torque is an indirect way to reach clamp load

Typical nut factor K (estimates; verify)

Condition

K

Plain steel, dry

0.20

Zinc plated, dry

0.20

Lubricated / oiled

0.15 - 0.18

Anti-seize compound

0.12 - 0.16

Hot-dip galvanized, lubricated nut

per manufacturer / RCSC

Key points

Most of the torque goes into friction; a small change in K is a large change in clamp load.

Never override an OEM or engineer torque with a chart value.

Governing standards: Industry practice; VDI 2230 for engineered joints. Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard

always take precedence over this sheet.

torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability

arising from reliance on this reference.

Fastener Guide reference FG-33242A · thefastenerapp.com/fastener-guide/technical-reference/torque-calculation-methods · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.

Related sheets

← Nickel-Alloy FastenersInch Torque Guide — Grades 2, 5, 8 →

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