Structural Bolt Torque Chart, ASTM F3125 A325 and A490 with RCSC Minimum Pretension

Published 23 September 2026. Last checked 29 September 2026. Part of the bolt torque chart set. For any other size, friction or preload, use the bolt torque calculator.

For structural bolts the number that matters is the pretension. The RCSC Specification for Structural Joints does not accept a torque from a table as a way to reach it. For pretensioned and slip-critical joints the 2025 edition requires turn-of-nut, twist-off tension-control bolts, direct tension indicators or the combined method (an initial torque from a calibrated installation wrench, then a specified rotation). The calibrated wrench method of earlier editions was withdrawn in 2025. The torque columns here are estimates for planning, wrench selection and checking that a calibrated value is plausible. They are not an installation method.

The pretension column is RCSC (2025) Table 5.2, unchanged from the 2020 edition. It is 0.70 × the minimum tensile strength × As rounded to the kip, where As is the tensile stress area. The minimum tensile strength under ASTM F3125 is 120 ksi for Grade A325 and 150 ksi for Grade A490.

Each torque column gives the torque that would produce that pretension. The columns use K 0.20 (plain, as received), K 0.15 (lubricated, as many A490 and weathering bolts are supplied) and the VDI 2230 thread-geometry method. That method takes μ 0.12 with a heavy hex head and a standard hole of d + 1/16 in. The "% of proof load" column shows how hard RCSC pretension works the bolt: close to 100 % for A325.

What the columns assume

Column	Basis
Thread	UNC 2A, as ASTM F3125 heavy hex structural bolts are supplied.
As	0.7854 (d − 0.9743/n)², in² (ASME B1.1).
Min tensile	ASTM F3125: 120 ksi A325, 150 ksi A490.
RCSC min pretension	RCSC Specification for Structural Joints (2025), Table 5.2, kip.
% of proof load	Pretension divided by the F3125 proof load (85 ksi A325, 120 ksi A490, × As).
Torque K 0.20 and K 0.15	T = K F d at the RCSC pretension.
Torque VDI 2230, μ 0.12	Heavy hex head bearing face about 0.95 × (1.5 d + 1/8 in) across flats (ASME B18.2.6), hole d + 1/16 in.
Calculate	Opens the calculator with the pretension entered as a direct preload.

Pretension and torque estimate, ASTM F3125 A325 and A490

ASTM F3125 structural bolt pretension and torque estimate
Thread	Grade	Torque K 0.20	Torque K 0.15	Torque VDI 2230, μ 0.12	RCSC min pretension (kip)	As (in²)	Min tensile (ksi)	% of proof load	Calculator
1/2-13 UNC	A325	100 lbf·ft	75.0 lbf·ft	85.4 lbf·ft	12	0.1419	120	99	Calculate
1/2-13 UNC	A490	125 lbf·ft	93.8 lbf·ft	107 lbf·ft	15	0.1419	150	88	Calculate
5/8-11 UNC	A325	198 lbf·ft	148 lbf·ft	166 lbf·ft	19	0.2260	120	99	Calculate
5/8-11 UNC	A490	250 lbf·ft	188 lbf·ft	210 lbf·ft	24	0.2260	150	88	Calculate
3/4-10 UNC	A325	350 lbf·ft	262 lbf·ft	289 lbf·ft	28	0.3345	120	98	Calculate
3/4-10 UNC	A490	438 lbf·ft	328 lbf·ft	361 lbf·ft	35	0.3345	150	87	Calculate
7/8-9 UNC	A325	569 lbf·ft	427 lbf·ft	464 lbf·ft	39	0.4617	120	99	Calculate
7/8-9 UNC	A490	715 lbf·ft	536 lbf·ft	583 lbf·ft	49	0.4617	150	88	Calculate
1-8 UNC	A325	850 lbf·ft	638 lbf·ft	689 lbf·ft	51	0.6057	120	99	Calculate
1-8 UNC	A490	1,067 lbf·ft	800 lbf·ft	865 lbf·ft	64	0.6057	150	88	Calculate
1-1/8-7 UNC	A325	1,200 lbf·ft	900 lbf·ft	971 lbf·ft	64	0.7633	120	99	Calculate
1-1/8-7 UNC	A490	1,500 lbf·ft	1,125 lbf·ft	1,213 lbf·ft	80	0.7633	150	87	Calculate
1-1/4-7 UNC	A325	1,688 lbf·ft	1,266 lbf·ft	1,348 lbf·ft	81	0.9691	120	98	Calculate
1-1/4-7 UNC	A490	2,125 lbf·ft	1,594 lbf·ft	1,698 lbf·ft	102	0.9691	150	88	Calculate
1-3/8-6 UNC	A325	2,223 lbf·ft	1,667 lbf·ft	1,781 lbf·ft	97	1.1549	120	99	Calculate
1-3/8-6 UNC	A490	2,773 lbf·ft	2,080 lbf·ft	2,221 lbf·ft	121	1.1549	150	87	Calculate
1-1/2-6 UNC	A325	2,950 lbf·ft	2,212 lbf·ft	2,341 lbf·ft	118	1.4053	120	99	Calculate
1-1/2-6 UNC	A490	3,700 lbf·ft	2,775 lbf·ft	2,937 lbf·ft	148	1.4053	150	88	Calculate

Source: RCSC Specification for Structural Joints Using High-Strength Bolts (5 June 2025), Table 5.2 and Section 8; ASTM F3125/F3125M-26 (strength); ASME B1.1-2019 (stress area). RCSC 2025: installation to the minimum pretension uses turn-of-nut, twist-off tension-control bolt, direct tension indicator or combined method pretensioning. A torque from this table is not an installation setting. See what changed in RCSC 2025.

Notes

Snug-tight joints need no pretension and no torque value. This chart is for pretensioned and slip-critical joints.
Galvanised A325 bolts with lubricated nuts are often nearer K 0.12 to 0.15. A490 may not be hot-dip galvanised.
The calculator shows how far the pretension would scatter with ±20 % friction variation for the same torque.
For general inch bolts see the SAE J429 chart. For metric bolts see the ISO 898-1 chart.