Reference tables · K-factor derived · Bolt Calculator

Bolt Torque Spec Chart — Metric & SAE Torque Tables by Grade

Fastener torque charts built the same way the Bolt Torque Calculator computes: preload at 75% of yield, T = K·F·d, K = 0.20 dry and 0.14 lightly oiled. Metric classes 8.8 / 10.9 / 12.9 from M6 to M24, SAE Grades 5 and 8 from 1/4-20 to 1-8, plus B7 stud, B8 stainless and 12.9 socket-screw specialty rows.

Metric table SAE table B7 · B8 · SHCS

The Method

How These Torque Specs Are Calculated

Every value in every table on this page comes from one equation applied consistently — the same T = K·F·d model the homepage calculator runs, so a number you read here can be reproduced there to the last N·m. The chain has exactly three steps:

1Pick the preload. F = 0.75 × yield × As, where As is the tensile stress area of the thread (ISO 68-1 for metric, ASME B1.1 for unified) and the yield is the minimum from ISO 898-1 (640 MPa for class 8.8, 940 for 10.9, 1100 for 12.9) or SAE J429 (92 ksi for Grade 5, 130 ksi for Grade 8).
2Pick the nut factor. K = 0.20 for clean, dry, zinc-plated or lightly rusted mild steel; K = 0.14 for a lightly oiled or anti-seized thread. These two columns — dry and oiled — are the two tables you get, and the 30% gap between them is the single biggest lever on any fastener torque chart.
3Multiply through. T = K × F × d. An M10 class 8.8 example: F = 0.75 × 640 × 58.0 = 27,840 N; T = 0.20 × 27,840 × 0.010 m = 55.7 ≈ 56 N·m dry, or 39 N·m oiled. That is the entire calculation — no hidden safety factor, no size-specific fudge.

One consistent standard, on purpose

Published bolt torque charts disagree with each other by ±20% because they anchor preload to different things: some use 75% of proof load (lower), some use 70% of yield, some use metric formulas with converted constants. This page deliberately inherits the homepage model — 75% of yield, K = 0.20/0.14 — so the chart, the strength check, and your hand calculation all land on the same number. The production reality is that assembly friction scatters ±20–30% anyway, which is why a target plus a min/max range beats a single sacred value.

Torque wrench and metric fasteners laid out on a workshop bench

One formula, every rowPhoto: Unsplash

Reading the K columns

“Dry” means as-plated or clean bare steel with no added lubricant (K ≈ 0.20). “Oiled” means one drop of machine oil or a wiped film of anti-seize on the threads and under the head (K ≈ 0.14). Anything wetter — grease-packed, MoS₂ paste — drops K further and the oiled column becomes optimistic; check the K table on the homepage for those cases.

Metric Torque Chart

Metric Bolt Torque Chart (ISO 898-1)

Coarse-series metric screws from M6 to M24. Values are the tightening torque at 75% of the grade’s minimum yield — the standard bolt torque chart layout: one dry column (K = 0.20) and one lubricated column (K = 0.14), plus the stronger grades so you can see what the same diameter is worth in 10.9 and 12.9 steel.

Size	Pitch (mm)	Class 8.8 Dry (N·m)	Class 8.8 Oiled (N·m)	Class 10.9 Dry (N·m)	Class 12.9 Dry (N·m)
M6	1.0	12	8	17	20
M8	1.25	28	20	41	48
M10	1.5	56	39	82	96
M12	1.75	97	68	143	167
M14	2.0	155	108	227	266
M16	2.0	241	169	354	414
M20	2.5	470	329	691	809
M24	3.0	813	569	1195	1398

Fine-Pitch Rows: M10×1.25, M12×1.25, M12×1.5

Fine-pitch fasteners carry a larger stress area on the same nominal diameter, so they take more torque for the same grade — the opposite of what the thinner thread suggests. Note for readers searching the M10×1.5 torque spec: that pitch is the standard M10 coarse series, so the M10 row above already answers it; the fine variant is M10×1.25.

Size	Series	Class 8.8 Dry (N·m)	Class 8.8 Oiled (N·m)	Class 10.9 Dry (N·m)	Class 12.9 Dry (N·m)
M10×1.25	1.25 (fine)	0	0	0	0
M12×1.25	1.25 (fine)	18	12	26	30
M12×1.5	1.5 (fine)	17	12	25	29

As values: M10×1.25 = 64.4 mm², M12×1.25 = 92.1 mm², M12×1.5 = 88.1 mm² per ISO 68-1. Class 8.8 yield 640 MPa, 10.9 yield 940 MPa, 12.9 yield 1100 MPa per ISO 898-1.

SAE Torque Chart

SAE Grade 5 & Grade 8 Torque Chart (ft·lb)

Unified coarse threads 1/4-20 through 1-8, torqued to 75% of minimum yield — 92 ksi for Grade 5, 130 ksi for Grade 8 per SAE J429. If you came here for the torque rating of bolts in ft·lb, this is the table to bookmark; the same rows convert at exactly 1.3558 N·m per ft·lb if your wrench reads metric.

Size	TPI	Grade 5 Dry (ft·lb)	Grade 5 Oiled (ft·lb)	Grade 8 Dry (ft·lb)	Grade 8 Oiled (ft·lb)
1/4-20	20	9	6	13	9
5/16-18	18	19	13	27	19
3/8-16	16	33	23	47	33
7/16-14	14	53	37	76	53
1/2-13	13	82	57	115	81
5/8-11	11	162	114	230	161
3/4-10	10	288	202	407	285
1-8	8	697	488	985	689

⚠️ Why some published charts read lower

Many classic SAE charts anchor preload to 75% of proof load (85 ksi for Grade 5) instead of yield, and some use K = 0.18–0.19. Either choice pulls the numbers down 10–20% — a 1-8 Grade 5 value of 536 ft·lb is a proof-load chart, not an error. Lower is not wrong; it is a different margin. When a drawing cites a value, the drawing governs. This table is the 75%-of-yield convention to match the homepage calculator.

Specialty Rows

B7 Studs, B8 Stainless, 12.9 Socket Screws & Small Threads

The three rows a general bolt torque chart always leaves out: ASTM B7 studs (petrochem flanges), ASTM B8 stainless (with its galling haircut), and the small socket-head cap screws where the useful unit switches to in·lb.

ASTM B7 Stud Bolts — dry, K = 0.20, 75% of 105 ksi yield

Stud Size	Dry Torque (ft·lb)	Typical Use
1/2-13	93	Small bore flanges, piping
5/8-11	185	CL150–CL300 flanges
3/4-10	329	CL300–CL600 flanges, pump covers
7/8-9	531	CL600 valves, equipment bases
1-8	795	CL900, heavy equipment
1-1/8-7	1023	CL900–CL1500
1-1/4-7	1590	CL1500+ large bore

ASTM B8 Stainless — dry, −10% from Grade 5

Size	B8 Dry Torque (ft·lb)	Condition
1/4-20	8	Class 2, strain-hardened — anti-seize strongly advised
5/16-18	17	Class 2, strain-hardened — anti-seize strongly advised
3/8-16	30	Class 2, strain-hardened — anti-seize strongly advised
1/2-13	74	Class 2, strain-hardened — anti-seize strongly advised
5/8-11	146	Class 2, strain-hardened — anti-seize strongly advised
3/4-10	259	Class 2, strain-hardened — anti-seize strongly advised

12.9 / A574 Socket Head Cap Screws — K = 0.20

Size	Dry Torque	Unit	Hex Key
4-40	2	in·lb	3/32″
6-32	4	in·lb	7/64″
8-32	6	in·lb	9/64″
10-24	7	ft·lb	5/32″
10-32	8	ft·lb	5/32″
1/4-28	18	ft·lb	3/16″
5/16-24	36	ft·lb	3/16″
3/8-24	66	ft·lb	5/16″
1/2-13	142	ft·lb	3/8″
5/8-11	283	ft·lb	1/2″
3/4-16	596	ft·lb	5/8″

#10 Small-Thread Rows — 10-24 vs 10-32

Thread	Grade 5 equiv. (in·lb)	Grade 8 equiv. (in·lb)
10-24 UNC	46	65
10-32 UNF	52	74

Machine-screw grades vary more than bolt grades — a “Grade 5 equivalent” #10 is an assumption, and many #10 screws are case-hardened or soft brass. Treat these as ceilings for steel machine screws, not targets for hardware-store screws of unknown pedigree.

The Two Columns

Dry vs. Oiled Torque: Why Every Chart Has Two Columns

Torque is a poor proxy for preload — roughly 85–90% of the work your wrench does is burned overcoming friction in the threads and under the head, and only the remaining 10–15% actually stretches the bolt. That is why the same M12 class 8.8 bolt needs 97 N·m dry but only 68 N·m oiled to reach the identical 39 kN of preload. The friction share changes, the clamp does not.

The dangerous direction is applying a dry value to a lubricated bolt. Run the 97 N·m dry spec on an oiled M12 and the real preload lands near 55 kN — about 140% of the 75%-of-yield target, deep into permanent stretch territory on a 12.9-grade bolt. The failure is not immediate; the bolt loses fatigue life and the joint loses clamp the first time it cycles. This is the single most common way a correct-looking chart ruins an assembly.

Match the column to the assembly condition — the condition at install, not at design. A spec that says “oiled” means someone oils every bolt, every time.
Coatings count as friction condition. Fresh zinc plating behaves near K = 0.20; waxed or phosphated parts closer to 0.16–0.18; black oxide with grit up to 0.25+.
Never mix charts. A 536 ft·lb proof-load chart value next to this page’s 697 ft·lb yield-load value describes the same bolt with different margins. Pick one convention per project.

Corner Cases

Four Torque-Spec Pitfalls That Snap Bolts

❌ Chart Override

OEM manual values always beat the chart

A generic fastener torque chart is a K-factor estimate for a hypothetical joint. Your engine manual, gearbox datasheet, or flange procedure is a measured spec for a real one. Where the two disagree by 10–20% — they will — the manual wins, full stop. Use this page for un-spec'd general hardware.

⚠️ Galling

Stainless dry-seizes at chart values

A2/A4 stainless threads gall under dry torque: friction spikes, the wrench climbs, preload doesn't. Use the B8 column (−10%), always lubricate, and slow the final turns to under 30 rpm. If a stainless nut suddenly needs more torque halfway down, stop — it is seizing, not tightening.

⚠️ Soft Base Thread

Aluminum hosts need a 0.5–0.6 derate

When the female thread is cut into aluminum or the clamp path includes soft alloy, the limiting stress is the host thread, not the bolt. Take the chart value × 0.5–0.6 (or use steel thread inserts to recover the full value). The bolt survives; the stripped hole is still a failed joint.

❌ Reuse Blindly

Second-run bolts don't follow the table

A reused bolt carries plating wear, thread debris, and work-hardened flanks. Measured K on second-run hardware scatters up to ±35% versus a fresh bolt. For critical joints, spec new fasteners; for reused ones, verify by angle or mark the rotation rather than trusting the wrench click alone.

Cross-System

Metric vs. SAE: Reading One Chart With the Other Wrench

A fastener torque chart is only valid for its own thread system. An M10 is not a 3/8-inch bolt — the M10 has a 10.0 mm major diameter against the 3/8″’s 9.525 mm, and the two carry different stress areas (58.0 vs 57.9 mm² — close — but different pitches and head sizes). The safe cross-reference is torque scale, not torque value: M10 class 8.8 (56 N·m dry) sits where a 3/8 Grade 5 (33 ft·lb ≈ 45 N·m) plus one size of margin would sit. Never torque a metric-marked bolt to an SAE chart number without recomputing from its own As and yield.

The same discipline applies inside a screw torque table: a #10-32 is not a #10-24 even though both are “#10” — the finer pitch raises the stress area from 17.5 to 19.9 thousandths of an in², and the specialty table above prices that difference at about 13% more torque. When the chart has no row for your exact thread, interpolate from the stress area, never from the nominal size.

FAQ

Bolt Torque Spec FAQ

The size-specific questions this chart gets asked most, answered with the same K-factor model that generated the tables.

What is the torque spec for an M10 bolt?

For a standard M10×1.5 class 8.8 bolt, dry, the spec works out to about 56 N·m (41 ft·lb). A class 10.9 takes roughly 82 N·m and a class 12.9 about 96 N·m. With light oil on the threads, drop those by 30% — around 39 N·m for the 8.8. All of these assume a K factor of 0.20 dry and 0.14 oiled and a preload target of 75% of yield.

What is the torque for a 1/4-20 bolt?

A 1/4-20 SAE Grade 5 tightened dry needs about 9 ft·lb; Grade 8 about 13 ft·lb. Lubricated, expect roughly 6 ft·lb and 9 ft·lb respectively. Hardware-store Grade 2 (unmarked) bolts should never see more than about 5 ft·lb — the head can shear well below the Grade 5 value.

How much torque can an M8 bolt take?

An M8×1.25 class 8.8 takes about 28 N·m dry (20 N·m oiled); class 10.9 about 41 N·m dry; class 12.9 about 48 N·m dry. These are calculated specs for fresh, clean fasteners — reused bolts with damaged zinc or grit in the threads can run 20–30% higher friction, which robs preload even though the wrench clicks.

Do I torque stainless steel bolts the same as carbon steel?

No — and this is the most common chart-reading mistake. A2/A4 stainless work-hardens and galls: the thread flanks weld microscopically as they slide, so the wrench torque climbs while the actual preload barely moves. Use the B8 column (≈90% of the Grade 5 value) and always run stainless with anti-seize or a suitable lubricant, reading the oiled column. For an exact number, the bolt torque calculator on the homepage lets you set a stainless-appropriate K factor directly.

What is the B7 stud torque for a 3/4-10 stud?

An ASTM B7 stud at 3/4-10 with a min yield of 105 ksi computes to roughly 329 ft·lb dry at 75% of yield with K = 0.20. In flange work studs are almost always lubricated with approved thread compound, so the working value is closer to 230 ft·lb — and most refinery procedures specify torque by stud size and lubricant brand, which overrides any generic table.

What is the maximum torque spec for a B8 bolt?

For ASTM B8 Class 2 (strain-hardened) studs and bolts, stay near 90% of the Grade 5 column: about 8 ft·lb for 1/4-20, 30 ft·lb for 3/8-16, 74 ft·lb for 1/2-13, dry. That 10% haircut is not a strength limit — Class 2 strength is close to Grade 5 — it is headroom for galling and the preload scatter stainless is famous for. Annealed B8 (Class 1, the ~30 ksi yield stuff) needs a specialist table entirely; do not guess from this chart.

How do you calculate HSFG bolt torque?

HSFG (high-strength friction grip) bolts are tightened not to a yield fraction but to a slip-critical preload — typically 0.7 × Fu × As per IS 1367 / IS 3757 practice for an 8.8 or 10.9 HSFG bolt. For an M20 HSFG bolt that is about 0.7 × 800 × 245 ≈ 137 kN of preload; with K = 0.14–0.18 the tightening torque lands near 385–495 N·m. Because HSFG performance depends entirely on the preload actually achieved, calibrated tools and washer-faced verification are part of the spec, not optional extras.

Is a torque rating in ft·lb the same as N·m converted?

Yes — 1 ft·lb is exactly 1.3558 N·m, so a 9 ft·lb spec is 12.2 N·m and the M10 56 N·m spec is 41.3 ft·lb. The columns in the tables above are generated independently in each unit system rather than converted, so rounding differences of 1–2 units between the two tables are normal and harmless.

Why does my equipment manual differ from this chart by 10–20%?

Because a published chart is a K-factor estimate and a manual is a measured spec. Manufacturers dyno-test real joints — real coatings, real washers, real embedment — and often target 60–70% of yield instead of 75%. A ±15% deviation between a generic chart and an OEM manual is normal and the manual always wins. This page's tables are engineering defaults for joints without a governing spec.

What torque does an M10×1.5 fine thread take — is it different from coarse?

M10×1.5 is the standard coarse pitch for M10 — the ordinary M10 row (56 N·m dry, class 8.8) applies. The fine variant is M10×1.25, and it takes slightly more torque: about 62 N·m dry for class 8.8, because the larger stress area (64.4 vs 58.0 mm²) raises the preload the same K factor produces. M12 has the same pattern: coarse 1.75 gives 97 N·m, while the 1.5 and 1.25 fine pitches give roughly 102 and 106 N·m.

Turn a Chart Number Into Your Spec

This bolt torque chart fixes K at 0.20 and 0.14 — the honest middle of each condition — but your joint may not be average: stainless with anti-seize, a heavily greased M20, or a plated 5/8-11 assembled with an impact wrench all shift K. Rather than interpolating a table, open the free bolt torque calculator on the homepage, enter your exact diameter, grade and lubrication, and read the torque plus the min/max assembly range your tool accuracy actually produces. The other bolt calculators cover the rest of the joint — shear, length, weight and bolt circles — so the whole specification stays in one consistent system.

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