Metric Bolt Torque Chart — Class 8.8, 10.9 & 12.9 (M4–M30)

Dry-torque reference values for metric bolts M4 through M30 in property class 8.8, 10.9, and 12.9, in both ft-lb and Nm. Use these as a general-assembly baseline — for vehicle fasteners (lug nuts, caliper bolts, head bolts) always use the OEM spec for your exact make and model.

How much torque for an M8, M10, or M12 bolt?

A clean, dry Class 8.8 bolt takes roughly 18 ft-lb at M8, 36 ft-lb at M10, and 63 ft-lb at M12. Class 10.9 runs about 40% higher (≈25 / 51 / 89 ft-lb) and 12.9 higher still. All values assume dry, unlubricated steel threads — reduce 15–25% for oiled, anti-seized, or zinc-plated fasteners.

What do 8.8, 10.9, and 12.9 mean?

They are metric property classes stamped on the bolt head. The first number is roughly the tensile strength (×100 MPa) and the second the yield-to-tensile ratio. Class 8.8 ≈ SAE Grade 5, 10.9 ≈ Grade 8, and 12.9 exceeds Grade 8 — a higher class holds more clamp load at the same size, so it takes more torque.

Dry vs lubricated torque

Every value here is dry torque. Lubrication lowers thread friction, so the same wrench reading produces more clamp load — enough to over-stretch or snap a fastener. If the spec calls for oil, anti-seize, or thread-locker, cut the dry value by about 15–25%.

When should I NOT use a generic torque chart?

Torque-to-yield (TTY) bolts, flange bolts, aluminum threads, and any OEM-specified fastener have their own numbers. Cylinder-head, main-cap, and connecting-rod bolts on modern engines are almost always TTY. For anything on a specific vehicle, look up the model rather than guessing from a generic chart.

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