How do you calculate bolt shear strength?

Multiply the nominal shear stress by the bolt's gross area and the number of shear planes: Rn = Fnv × πd²/4 × n. AISC 360 sets Fnv = 0.450 Fu when threads are in the shear plane and 0.563 Fu when they are excluded. For LRFD multiply by φ = 0.75; for ASD divide by Ω = 2.00.

What is the shear capacity of a 3/4 in A325 bolt?

In single shear with threads in the shear plane (A325-N), Rn = 54 ksi × 0.442 in² = 23.9 kips, so φRn = 17.9 kips (LRFD) and Rn/Ω = 11.9 kips (ASD). With threads excluded (A325-X), Fnv = 68 ksi gives φRn = 22.5 kips and Rn/Ω = 15.0 kips. Double shear doubles these values for the bolt itself.

What is the shear resistance of an M20 8.8 bolt to Eurocode 3?

EN 1993-1-8 gives Fv,Rd = αv × fub × A ÷ γM2. With the shear plane through the threads, αv = 0.6, fub = 800 MPa and As = 245 mm², so Fv,Rd = 0.6 × 800 × 245 ÷ 1.25 = 94.1 kN per shear plane. Through the plain shank, A = 314 mm² gives 120.6 kN. A 10.9 bolt through the threads uses αv = 0.5 and gives 98.0 kN.

What is the difference between single and double shear?

Single shear has one potential shear plane; double shear has two. This calculator doubles bolt-only nominal area for two planes, but bearing, tear-out, eccentricity, unequal load distribution and connected-part strength can prevent the whole joint from gaining exactly twice the usable capacity.

Is bolt shear strength 60% of tensile strength?

Roughly. Steel fails in shear at about 0.6 times its tensile strength, so a common estimate of ultimate shear is 0.6 × Fu × area, using the tensile stress area when threads cross the plane. AISC builds in further reductions for design: 0.563 Fu with threads excluded and 0.450 Fu with threads included, then φ = 0.75.

What tensile strength values are used for each grade?

ASTM: A307 60 ksi, A325 120 ksi, A490 150 ksi (AISC Fnv taken directly: 27, 54/68 and 68/84 ksi). SAE J429: Grade 2 74 ksi to 3/4 in and 60 ksi above, Grade 5 120 ksi to 1 in and 105 ksi above, Grade 7 133 ksi, Grade 8 150 ksi. ISO 898-1 minimums: 4.6 400, 4.8 420, 5.6 500, 5.8 520, 6.8 600, 8.8 800 MPa to M16 and 830 MPa above, 10.9 1040, 12.9 1220 MPa.

Does this give the IS 800 design strength of an M20 grade 4.6 bolt?

No. IS 800:2007 takes fu ÷ √3, divides it by the partial safety factor 1.25 and uses the net tensile stress area (245 mm² for M20) where threads cross a plane, so its double-shear design value with both planes through the threads is about 90.5 kN. This tool reports AISC and Eurocode values, so the numbers differ.

Does this complete a bolted-joint design?

No. It does not check bearing, tear-out, net-section rupture, block shear, slip, preload, combined tension and shear, fatigue, eccentric bolt groups, long-joint reductions, thread stripping, hole type or filler plates. A qualified engineer must check the full connection.

Bolt Shear Strength Calculator

Pick a bolt grade (A325, A490, A307, SAE or ISO), diameter, single or double shear and thread condition to get AISC LRFD and ASD design strength, Eurocode 3 shear resistance and an ultimate shear estimate in kN, lbf and kip.

Nominal bolt shear Rn = Fnv × Ab × shear planes, where Ab = πd²/4 and Fnv is 0.450 Fu with threads in the shear plane or 0.563 Fu with threads excluded (AISC 360).

Bolt Parameters

Bolt Standard

ASTM structural SAE (inch) ISO (metric)

Grade / Class

Nominal Bolt Diameter

Shear Type

Single shear Double shear

Threads at Shear Plane Included (N) — conservative default; plane crosses threads Excluded (X) — plane is proven to cross full shank only

Your Safety Factor (divides nominal Rn)

Shear Area

—

mm² total

Nominal Shear Rn

—

AISC LRFD Design Strength φRn

—

Capacity by Design Method

Method	kN	kip
Enter values and click Calculate.

Bolt shear only. The result does not establish connection capacity. Check the governing code and all connected-part, hole, bearing, tear-out, slip, fatigue, tension interaction and load-distribution limit states.

Calculation Breakdown

Enter values and click Calculate.

A325 and A490 Bolt Shear Capacity per Bolt (AISC LRFD, single shear)

φRn = 0.75 × Fnv × Ab in kips, Ab = πd²/4. N = threads included, X = threads excluded. Double shear = 2×. ASD Rn/Ω = φRn ÷ 1.5.

Diameter	Ab (in²)	A325-N	A325-X	A490-N	A490-X
1/2 in	0.196	8.0	10.0	10.0	12.4
5/8 in	0.307	12.4	15.6	15.6	19.3
3/4 in	0.442	17.9	22.5	22.5	27.8
7/8 in	0.601	24.4	30.7	30.7	37.9
1 in	0.785	31.8	40.1	40.1	49.5
1-1/8 in	0.994	40.3	50.7	50.7	62.6
1-1/4 in	1.227	49.7	62.6	62.6	77.3
1-3/8 in	1.485	60.1	75.7	75.7	93.5
1-1/2 in	1.767	71.6	90.1	90.1	111.3

Metric Bolt Shear Resistance Fv,Rd (Eurocode 3, per shear plane)

Fv,Rd = αv × fub × As ÷ γM2 in kN with the shear plane through the threads, γM2 = 1.25. αv = 0.6 for 4.6 and 8.8, 0.5 for 10.9.

Size	As (mm²)	4.6	8.8	10.9
M12	84.3	16.2	32.4	33.7
M16	157	30.1	60.3	62.8
M20	245	47.0	94.1	98.0
M24	353	67.8	135.6	141.2
M27	459	88.1	176.3	183.6
M30	561	107.7	215.4	224.4
M36	817	156.9	313.7	326.8

Bolt Grade Strength Reference

Grade	Min. tensile Fu	Fnv, threads in (N)	Fnv, threads out (X)
ASTM A307	60 ksi (414 MPa)	27 ksi	27 ksi
ASTM A325 / F3125 (Group A)	120 ksi (827 MPa)	54 ksi	68 ksi
ASTM A490 / F3125 (Group B)	150 ksi (1,034 MPa)	68 ksi	84 ksi
SAE Grade 2 (≤ 3/4 in)	74 ksi (510 MPa)	33.3 ksi	41.7 ksi
SAE Grade 5 (≤ 1 in)	120 ksi (827 MPa)	54.0 ksi	67.6 ksi
SAE Grade 8	150 ksi (1,034 MPa)	67.5 ksi	84.5 ksi
ISO 4.6	400 MPa	180 MPa	225 MPa
ISO 8.8 (≤ M16 / > M16)	800 / 830 MPa	360 / 374 MPa	450 / 467 MPa
ISO 10.9	1,040 MPa	468 MPa	586 MPa
ISO 12.9	1,220 MPa	549 MPa	687 MPa

ASTM values are AISC 360 Table J3.2 entries; SAE and ISO values apply the same 0.450 Fu / 0.563 Fu factors to SAE J429 and ISO 898-1 minimum tensile strengths.

Method, worked examples & sources

AISC 360 (J3.6): Rn = Fnv × Ab per shear plane, with Ab the gross (unthreaded) area. The thread effect is in Fnv. LRFD: φ = 0.75. ASD: Ω = 2.00. Example: 7/8 in A325-N in double shear: 54 × 0.601 × 2 = 64.9 kips nominal, φRn = 48.7 kips.

Eurocode 3 (EN 1993-1-8, Table 3.4): Fv,Rd = αv × fub × A ÷ γM2. Through the threads, A = tensile stress area As and αv = 0.6 (4.6, 5.6, 8.8) or 0.5 (4.8, 5.8, 6.8, 10.9). Through the shank, A = gross area and αv = 0.6. fub is the nominal class value (800 MPa for 8.8, 1000 MPa for 10.9); class 12.9 is outside EN 1993-1-8.

0.6 Fu rule of thumb: ultimate shear ≈ 0.6 × Fu × A, with As when threads cross the plane. It estimates failure load, not a design value.

AISC 360 specification and commentary · AISC bolting FAQs. Calculations run in your browser; entered dimensions are not uploaded.

Quick answer

Nominal bolt shear Rn = Fnv × Ab × shear planes, where Ab = πd²/4 and Fnv is 0.450 Fu with threads in the shear plane or 0.563 Fu with threads excluded (AISC 360). A325 bolts use Fnv = 54/68 ksi and A490 68/84 ksi. LRFD design strength is 0.75 Rn; ASD allowable is Rn/2.00.

Examples

Bolt and shear case	Nominal Rn	Design value
3/4 in A325-N, single	23.9 kip	φRn 17.9 kip · Rn/Ω 11.9 kip
3/4 in A490-X, single	37.1 kip	φRn 27.8 kip · Rn/Ω 18.6 kip
M20 8.8, single, threads in plane	117.3 kN (AISC, Fu 830 MPa)	EC3 Fv,Rd 94.1 kN
M20 10.9, single, threads in plane	147.0 kN (AISC)	EC3 Fv,Rd 98.0 kN
M20 4.6, double, threads in plane	113.1 kN	EC3 Fv,Rd 94.1 kN
5/8 in SAE Grade 8, single	92.1 kN (20,709 lbf)	φRn 69.1 kN

Pick the grade, diameter and shear case to get AISC, Eurocode and ultimate shear capacity in kN, lbf and kip.

Summary

How it works

Select the bolt standard (ASTM structural, SAE or ISO) and choose a grade or property class.
Enter the nominal bolt diameter and select the diameter unit (mm or inches).
Choose single or double shear and state whether threads cross the shear plane.
Click Calculate to see nominal shear Rn, AISC LRFD φRn and ASD Rn/Ω, Eurocode 3 Fv,Rd for metric classes, and a 0.6 Fu ultimate estimate.
Optionally enter your own safety factor to divide the nominal strength by it.

Use cases

Checking A325 or A490 bolt shear in a steel connection (LRFD or ASD).
Finding the Eurocode 3 shear resistance of an M16–M30 8.8 or 10.9 bolt.
Verifying fastener capacity in machine frames and brackets.
Comparing SAE vs. ISO bolt grades for a given load requirement.
Checking double-shear clevis joints in mechanical linkages.
Quick design checks before detailed connection design.

Frequently Asked Questions

Last updated: 2026-10-09 · Reviewed by Nham Vu