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Bolt torque, grades and vehicle specs, sourced

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Lubricated torque calculator (dry to oiled, anti-seize, moly)

Enter the specified torque, the thread condition it was written for, and the condition you are actually using. The calculator scales the torque by the ratio of nut factors so the clamp load stays the same: 100 ft-lb dry becomes 80 ft-lb with copper anti-seize (K 0.16).

By the Torque Reference editors 11 sources cited Last reviewed Method
Contents6 sections

80 ft-lb for the same clamp load100 × 0.16 ÷ 0.20 = 80: a 20% reduction from the dry value.

Only scale a torque when you know what condition the original value assumed. A manufacturer’s spec already includes its own assumption; follow it as written.

Key takeaways

  • Same clamp load means same K × T, so T_new = T_spec × K_new ÷ K_spec. Torque scales with the nut factor, not by a fixed percentage.
  • From plain dry (K 0.20): oil is 25% less, copper anti-seize 20% less, moly paste 45% less.
  • A dry torque applied to moly-coated threads drives the clamp load to about 136% of proof load: past proof, into yield territory.
  • Do not scale a manufacturer's spec that says to keep threads dry, such as wheel studs ⁠1 or NGK spark plugs ⁠2.

Quick facts

FormulaT_new = T_spec × K_new ÷ K_spec
Plain dryK 0.20 ⁠3
OiledK 0.15 ⁠3
Copper anti-seizeK 0.16 ⁠4
Moly pasteK 0.11 ⁠5

How it works

Torque and clamp load are tied by T = K × D × F ⁠3. The diameter does not change when you oil a bolt, so to keep the same clamp load F the product K × T has to stay constant. That gives one line:

T_new = T_spec × K_new ÷ K_spec

The two dropdowns use the site’s five nut factors: 0.20 plain dry, 0.18 zinc-plated dry and 0.15 lubricated from the notes to Fastenal’s torque tables ⁠3, 0.16 copper or metal-free anti-seize from the LOCTITE C5-A data sheet ⁠4, and 0.11 moly paste from the LOCTITE moly paste data sheet ⁠5. The unit you type in is the unit you get back. The result shows one decimal under 20, whole numbers above.

The calculator never stacks a percentage on top of a K value. If you start from a spec already written for oiled threads and pick “lubricated” in both boxes, the answer is the spec itself.

Worked example

A bracket bolt is specified at 100 ft-lb, plain dry, and you have moly paste on the threads.

100 ft-lb dry spec, three thread conditions
You are using K Torque for the same clamp load Change
Plain dry 0.20 100 ft-lb –
Lubricated (oil or grease) 0.15 75 ft-lb 25% less
Copper anti-seize 0.16 80 ft-lb 20% less
Moly paste 0.11 55 ft-lb 45% less

Scroll the table sideways to see every column.

For moly: 100 × 0.11 ÷ 0.20 = 55 ft-lb.

It works the other way too. The bolt torque calculator gives 70 ft-lb for an oiled M12 class 10.9 bolt. If that bolt goes in dry instead, 70 × 0.20 ÷ 0.15 = 93 ft-lb, the dry value from the same calculator.

Reading the result

The result is the torque that should give the clamp load the original spec was aiming for. It is only as good as the condition the original spec assumed. If you don’t know whether a spec was written dry or lubricated, the calculator cannot tell you, and guessing wrong is the error you were trying to avoid.

The anti-seize and moly values come from Henkel tests on specific hardware: a 1/2 in. Grade 8 bolt with a Grade 5 nut ⁠4 ⁠5. Henkel measured K 0.27 for the same hardware solvent cleaned and unlubricated ⁠4, which is drier than the 0.20 “plain dry” used here. On phosphate-coated Grade 5 hardware the copper anti-seize stick measured 0.16 against a 0.19 dry baseline ⁠6. So the reduction from dry to anti-seize ranges from about 16% to about 41% depending on what “dry” was. The site uses 0.20 as its dry baseline so that all its ratios are consistent with its charts.

Common mistakes

  • Applying a dry torque to lubricated threads. With moly paste, the same 100 ft-lb produces 0.20 ÷ 0.11 = 1.82 times the intended clamp load. A bolt meant to sit at 75% of proof ends up near 136% of proof. Fastenal’s own example shows an over-lubricated 1/2-13 Grade 5 bolt at K 0.10 reaching 18,100 lb at its normal torque, more than the bolt’s tensile strength ⁠3.
  • Using a flat “reduce by X%” rule. Rules of thumb like “take 25% off for anti-seize” ignore which compound and which baseline. Use the K of what you actually applied.
  • Scaling a maker’s spec that forbids lubricant. Ram’s owner’s manual says “Do not oil wheel studs” next to its lug nut torque ⁠1. NGK says not to use anti-seize or lubricant on its spark plugs ⁠2. In those cases the answer is to keep the threads clean and dry, not to recalculate.
  • Treating thread locker as a lubricant. LOCTITE 242 is rated to change K by no more than ±10% ⁠7, so it is closer to dry than to oiled, and Henkel publishes no lubricity figure for 243, 262 or 271 ⁠8 ⁠9 ⁠10. See thread locker and torque.
  • Lubricating only one surface. NASA notes that the torque-preload relationship changes noticeably between lubricating only under the head and lubricating under the head and the nut ⁠11. Apply lubricant the same way every time.

For the background on nut factors and where each one comes from, read dry vs lubricated torque.

Sources

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  11. 11

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