Metric coarse M10 to M125 • Class 8.8, 10.9, 12.9 • ISO 898-1

Bolt Tightening Torque Calculator The torque you need for a 70% of proof load preload

Pick the bolt size, property class and lubrication. We give you the target preload and the tightening torque in N·m and ft·lb, worked out the same way as our published one-pager.

Calculate the torque → Available sizes

Torque Calculator

Bolt size (metric coarse) d = 24 mm, P = 3 mm, A_s = 353 mm²

Property class (ISO 898-1) Proof stress 830 MPa

Lubrication Sets the k-factor (nut factor).

k-factor (nut factor) Typing a value switches lubrication to custom. Usual range 0.10 to 0.30.

Preload, % of proof load 70% to 85%. Our tables use 70%.

Show torque in 1 N·m = 0.7376 ft·lb

205.1Preload F [kN]

753.1Tightening torque T [N·m]

555.5Tightening torque [ft·lb]

Proof load (100%): 293.0 kN
Bolt stress at preload: 581 MPa
Formula: T = 0.153 × 205.1 kN × 24 mm

Results update as you change the inputs. Preload and torque are rounded to 0.1, exactly as in our published tables.

PRELOAD, PROOF LOAD AND K-FACTOR

How It Works

The calculator uses the short-form torque equation that the industry, and our own one-pager, relies on:

T = k \cdot F \cdot d

T = tightening torque [N·m] (with F in kN and d in mm, the result is directly in N·m)
k = the k-factor or nut factor, which lumps together the friction in the threads and under the nut or bolt head
F = the target preload (clamp load) [kN]
d = the nominal thread diameter [mm]

Target preload

The target preload is a percentage of the bolt’s proof load. Proof load is the proof stress of the property class (ISO 898-1) multiplied by the nominal stress area A_s of the thread. We work to 70% of proof load (G_F = 0.7), which leaves a reasonable margin of safety. The calculator lets you choose between 70% and 85%:

F = G_{F} \cdot S_{p} \cdot A_{s}

Proof stress S_p used (ISO 898-1)
Property class	8.8 (≤ M16)	8.8 (> M16)	10.9	12.9
Proof stress [MPa]	580	600	830	970
Stress at 70% [MPa]	406	420	581	679

Lubrication and the k-factor

Up to 90% of the tightening torque is lost to friction, so the lubrication changes the torque you need far more than the bolt does. The same preload needs about 67% more torque on a dry bolt than on one lubricated with graphite grease.

k-factors used in our tables
Lubrication	k-factor	Friction assumed
Graphite Grease	0.153	μ_th = 0.10, μ_h = 0.12
WD40 oil	0.206	μ_th = 0.10, μ_w = 0.20
Dry	0.256	–

μ_th = thread friction coefficient; μ_h, μ_w = friction coefficient under the head or washer.

ALL SIZES AT 70% OF PROOF LOAD

Torque Table, M10 to M125

All sizes at 70% of proof load, for Graphite Grease (k 0.153), WD40 oil (k 0.206) and Dry (k 0.256). See also our torque and preload one-pager.

Preload at 70% of proof load and tightening torque [N·m], metric coarse thread
Bolt	Class 8.8				Class 10.9				Class 12.9
Bolt	Preload [kN]	k 0.153	k 0.206	k 0.256	Preload [kN]	k 0.153	k 0.206	k 0.256	Preload [kN]	k 0.153	k 0.206	k 0.256
M10	23.5	36.0	48.4	60.2	33.7	51.6	69.4	86.3	39.4	60.3	81.2	100.9
M12	34.2	62.8	84.5	105.1	49.0	90.0	121.1	150.5	57.3	105.2	141.6	176.0
M14	46.7	100.0	134.7	167.4	66.9	143.3	192.9	239.8	78.1	167.3	225.2	279.9
M16	63.7	155.9	210.0	260.9	91.2	223.3	300.6	373.6	106.6	261.0	351.4	436.6
M18	80.5	221.7	298.5	370.9	111.3	306.5	412.7	512.9	130.4	359.1	483.5	600.9
M20	102.9	314.9	423.9	526.8	142.1	434.8	585.5	727.6	166.3	508.9	685.2	851.5
M22	127.3	428.5	576.9	717.0	175.7	591.4	796.3	989.5	205.8	692.7	932.7	1 159.1
M24	148.3	544.6	733.2	911.2	205.1	753.1	1 014.0	1 260.1	239.6	879.8	1 184.6	1 472.1
M27	192.6	795.6	1 071.2	1 331.3	266.7	1 101.7	1 483.4	1 843.4	311.7	1 287.6	1 733.7	2 154.5
M30	235.8	1 082.3	1 457.2	1 810.9	326.2	1 497.3	2 015.9	2 505.2	380.8	1 747.9	2 353.3	2 924.5
M33	291.6	1 472.3	1 982.3	2 463.4	403.2	2 035.8	2 741.0	3 406.2	471.1	2 378.6	3 202.5	3 979.9
M36	343.0	1 889.2	2 543.7	3 161.1	474.6	2 614.1	3 519.6	4 373.9	554.8	3 055.8	4 114.4	5 113.0
M39	410.2	2 447.7	3 295.5	4 095.4	567.0	3 383.3	4 555.3	5 660.9	662.9	3 955.5	5 325.7	6 618.4
M42	470.4	3 022.8	4 069.9	5 057.7	650.7	4 181.4	5 629.9	6 996.3	760.5	4 887.0	6 579.8	8 176.9
M45	550.2	3 788.1	5 100.4	6 338.3	761.1	5 240.2	7 055.4	8 767.9	889.5	6 124.2	8 245.7	10 247.0
M48	617.4	4 534.2	6 104.9	7 586.6	854.1	6 272.5	8 445.3	10 495.2	998.1	7 330.0	9 869.2	12 264.7
M52	739.2	5 881.1	7 918.3	9 840.2	1 022.6	8 135.8	10 954.1	13 612.9	1 195.0	9 507.4	12 800.8	15 907.8
M56	852.6	7 305.1	9 835.6	12 222.9	1 179.4	10 105.1	13 605.6	16 907.9	1 378.4	11 810.1	15 901.2	19 760.7
M60	991.2	9 099.2	12 251.2	15 224.8	1 371.2	12 587.6	16 948.0	21 061.6	1 602.4	14 710.0	19 805.7	24 612.9
M64	1 125.6	11 021.9	14 839.9	18 441.8	1 557.1	15 247.1	20 528.8	25 511.5	1 819.7	17 818.5	23 990.9	29 814.0
M68	1 285.2	13 371.2	18 003.1	22 372.8	1 777.9	18 497.3	24 904.8	30 949.7	2 077.7	21 616.4	29 104.4	36 168.6
M72	1 440.6	15 869.6	21 367.0	26 553.1	1 992.8	21 952.7	29 557.2	36 731.3	2 329.0	25 656.3	34 543.7	42 928.1
M76	1 620.4	18 842.0	25 369.0	31 526.5	2 241.5	26 064.2	35 092.9	43 610.6	2 619.6	30 460.7	41 012.5	50 966.9
M80	1 810.6	22 161.7	29 838.7	37 081.1	2 504.7	30 657.5	41 277.5	51 296.3	2 927.2	35 828.9	48 240.3	59 949.1
M85	2 063.0	26 829.3	36 123.1	44 890.9	2 853.9	37 115.0	49 971.8	62 100.9	3 335.2	43 374.3	58 399.4	72 574.0
M90	2 332.3	32 115.8	43 240.8	53 736.2	3 226.3	44 426.2	59 815.6	74 334.0	3 770.5	51 919.8	69 905.1	86 872.3
M95	2 617.9	38 051.2	51 232.3	63 667.3	3 621.4	52 637.0	70 870.8	88 072.4	4 232.2	61 515.0	82 824.2	102 927.1
M100	2 919.8	44 672.9	60 147.9	74 746.9	4 039.1	61 798.2	83 205.5	103 401.0	4 720.4	72 222.1	97 240.2	120 842.2
M105	3 238.6	52 028.1	70 050.9	87 053.6	4 480.1	71 972.8	96 904.6	120 425.1	5 235.8	84 113.1	113 250.4	140 738.3
M110	3 573.8	60 147.1	80 982.3	100 638.2	4 943.7	83 202.5	112 024.2	139 214.6	5 777.6	97 237.0	130 920.4	162 697.2
M115	3 925.3	69 065.7	92 990.4	115 560.8	5 430.0	95 540.9	128 636.7	159 859.2	6 345.9	111 656.1	150 334.4	186 823.3
M120	4 293.2	78 823.2	106 127.9	131 887.1	5 939.0	109 040.0	146 812.1	182 446.1	6 940.7	127 431.3	171 574.1	213 218.3
M125	4 524.2	86 525.3	116 498.2	144 774.4	6 258.5	119 693.8	161 156.4	200 272.0	7 314.2	139 884.1	188 340.7	234 054.4

A GUIDE, NOT A GUARANTEE

Disclaimer

Please read before you tighten

This calculator and the table are a guide only. The short-form equation T = k·F·d is an estimate: the real k-factor depends on the surface finish, coating, plating, lubricant, thread tolerance, washer, tightening speed and tool, and it can easily vary by ±25% or more. The same torque can therefore give a very different preload.

Values assume ISO 898-1 bolts with metric coarse threads, matching nuts of the correct class, and a correctly designed joint. They do not allow for prevailing torque (lock nuts), damaged or reused threads, soft clamped parts, gaskets, or high temperatures. For critical joints, verify the preload by measurement (bolt elongation, ultrasonic or load-indicating methods), and follow the bolt or equipment manufacturer’s instructions where they differ.

Reliable Pressings accepts no liability for any loss or damage arising from the use of these values. If in doubt, ask us.

Keep that preload where you set it

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