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Bolt Torque Chart

Recommended assembly torque for SAE Grade 2/5/8, ISO 8.8/10.9/12.9, and stainless A2-70 fasteners — dry and lubricated.

True Precision Machining
Section view of a bolted joint: a socket-head cap screw clamping two plates, with applied torque T at the head, clamp force F through the joint, and friction losses under the head and in the threads. The formula T equals K times D times F is shown with friction factor K of 0.20 dry and 0.15 oiled, and a bar showing that roughly 90 percent of applied torque is lost to friction, leaving only about 10 percent as bolt stretch and clamp force. T (TORQUE) CLAMP FORCE F CLAMP FORCE F ~90% LOST TO FRICTION D (NOM Ø) BOLTED JOINT — SECTION Torque is a proxy — what the joint actually needs is clamp force F. T = K · D · F TORQUE (IN-LB) = FRICTION FACTOR × NOMINAL Ø (IN) × PRELOAD (LBF) K = FRICTION FACTOR: DRY 0.20 · OILED 0.15 ~90% LOST TO FRICTION (TYPICAL) UNDER-HEAD ~50% THREADS ~40% CLAMP (STRETCH) ~10% WHERE THE TORQUE GOES Friction eats ~90% of the torque — which is why lubrication changes the number.
Size Aₜ in² Recommended assembly torque — ft-lb @ 75% yield preload
SAE Grade 2 inch only 57 ksi yield SAE Grade 5 metric: ISO 8.8 92 ksi yield SAE Grade 8 metric: ISO 10.9 130 / 136 ksi yield ISO 12.9 160 ksi yield A2-70 SS 65 ksi yield
Dry Oiled Dry Oiled Dry Oiled Dry Oiled Dry Oiled
Inch — Unified coarse (UNC)
1/4-20 0.0318 5.7 4.2 9.1 6.9 13 9.7 16 12 6.5 4.8
5/16-18 0.0524 12 8.8 19 14 27 20 33 25 13 10.0
3/8-16 0.0775 21 16 33 25 47 35 58 44 24 18
7/16-14 0.1063 33 25 53 40 76 57 93 70 38 28
1/2-13 0.1419 51 38 82 61 115 86 142 106 58 43
9/16-12 0.1820 73 55 118 88 166 125 205 154 83 62
5/8-11 0.2260 101 75 162 122 230 172 283 212 115 86
3/4-10 0.3340 178 134 288 216 407 305 501 376 204 153
7/8-9 0.4620 182 136 465 349 657 493 809 606 328 246
1-8 0.6060 273 205 697 523 985 739 1,212 909 492 369
Metric — ISO coarse
M5 0.0220 — — 5.0 3.7 7.4 5.5 8.7 6.5 3.5 2.6
M6 0.0312 — — 8.5 6.4 13 9.4 15 11 6.0 4.5
M8 0.0568 — — 21 15 30 23 36 27 15 11
M10 0.0900 — — 41 31 60 45 71 53 29 22
M12 0.1310 — — 71 53 105 79 124 93 50 38
M16 0.2430 — — 176 132 260 195 306 230 124 93
M20 0.3800 — — 344 258 509 381 598 449 243 182

Key: all values in ft-lb at 75% of yield preload. Dry = uncoated steel-on-steel, K = 0.20. Oiled = light oil / wax, K = 0.15. Aₜ = thread tensile stress area (in²).

T = K × D × F, where F = 0.75 × yield × tensile area. SAE Grade 5 (92 ksi) ≈ ISO 8.8 (92 ksi); SAE Grade 8 (130 ksi) ≈ ISO 10.9 (136 ksi) — metric rows in those columns are computed at the ISO value. Grade 2 is inch-only (— on metric rows). A2-70 = 304 stainless. Per SAE J429, Grade 2 yield drops to 36 ksi over 3/4″ dia — the 7/8-9 and 1-8 rows use 36 ksi.

Reduce torque 30–50% in tapped holes of soft material (aluminum, plastics) to protect the threads. For lubrication factors not shown (zinc K = 0.18, anti-seize K = 0.12, PTFE K = 0.09) and any size, grade, or preload combination, use the interactive bolt torque calculator.

Free engineering reference from True Precision Machining
trueprecisionmachining.com · 805-964-4545 · Buellton, CA · AS9100 / ISO 9001 / ITAR
Torque at 75% of yield preload, T = K·D·F — verify against OEM specs for critical joints. · September 2026