Bolt Tensile & Shear Capacity Calculator

What this tool does

Returns the allowable tension and shear for a structural bolt by grade and diameter, and multiplies out to a bolt group. Covers ASTM A307, ASTM F3125 Grade A325 and A490, ASTM A449, the F3125 metric structural grades A325M and A490M, SAE J429 grades and the ISO metric property classes. Select a grade to tabulate every standard diameter; the load check uses the selected grade and a size dropdown.

Results are ASD bolt-strength allowables for a bearing-type connection with one shear plane, threads included, based on the gross nominal shank area. Bolt strength only; connection limit states and installation requirements are not covered.

Formula

Two methods, depending on the fastener class. The ASTM grades divide a nominal stress by Ω = 2.00 — off Table J3.2 for A307, A325, A490 and the metric A325M and A490M, and off the threaded-part rule for A449. SAE J429 and ISO are material specs with no published allowables, so those grades use a Quick Ref method: ultimate strength (nominal yield for ISO) over a 2.5 factor of safety. These are STL calculated reference values, not SAE, ISO or AISC design allowables, and not a connection basis.

Assumptions

The fastener classes below do not share a basis: read the one that matches your fastener. An ASTM structural grade and an SAE J429 or ISO property class are not equivalent — the first carries AISC design values, the second an STL Quick Ref reference calculation — and the two are never interchangeable in a connection check.

• ASTM Structural Bolts — A307, A325, A490AISC Table J3.2 nominal stresses with Ω = 2.00; threads included in shear plane.
  • A307: Fnt = 45 ksi / Fnv = 27 ksi
  • A325: Fnt = 90 ksi / Fnv = 54 ksi
  • A490: Fnt = 113 ksi / Fnv = 68 ksi
• ASTM A449AISC 360 Section A3.4 threaded-part provisions with Ω = 2.00; threads included in shear plane.
  • ≤ 1 in.: Fu = 120 ksi → Fnt = 90 / Fnv = 54 ksi
  • 1-1/8–1-1/2 in.: Fu = 105 ksi → Fnt = 78.8 / Fnv = 47.3 ksi
  • > 1-1/2 in.: Fu = 90 ksi → Fnt = 67.5 / Fnv = 40.5 ksi
• SAE J429STL Quick Ref method; not an AISC structural connection design basis. Ultimate strength divided by 2.5.
  • Grade 1: Fu = 60 ksi
  • Grade 2: Fu = 74 ksi ≤ 3/4 in.; 60 ksi > 3/4 in.
  • Grade 5: Fu = 120 ksi ≤ 1 in.; 105 ksi > 1 in.
  • Grade 8: Fu = 150 ksi
  • Machine fasteners; use ASTM structural grades for structural connections.
• Metric Structural Bolts — A325M, A490MAISC Table J3.2 approach with Ω = 2.00; threads included in shear plane.
  • A325M: Fnt = 620 MPa / Fnv = 372 MPa
  • A490M: Fnt = 780 MPa / Fnv = 469 MPa
  • Applicable range: M12–M36.
• ISO Metric Property Classes — 4.6, 8.8, 10.9STL Quick Ref method; not an AISC or ISO 898-1 structural connection design basis. Uses gross nominal area, Ab = πd²/4, with a 2.5 factor of safety.
  • 4.6: Nominal Yield Strength = 240 MPa
  • 8.8: Nominal Yield Strength = 640 MPa
  • 10.9: Nominal Yield Strength = 900 MPa
  • These are nominal yield strengths used in the STL reference calculation and are not ISO 898-1 design allowables.
• Design Method: ASD; allowable = nominal/ultimate capacity divided by the applicable safety factor.
• Shear: Single shear plane with threads included. Group capacity = number of bolts × single-bolt capacity.
• Tension + Shear: Checked independently. Combined loading requires a separate AISC J3.7 interaction check; not included.
• Connection Type: Bearing-type connections only.
• Slip-critical connections: Not covered by this tool. Additional design and installation requirements apply.
• Installation: Snug-tight installation is permitted only where allowed by AISC/RCSC; pretensioning may be required depending on the application (e.g. A490 in tension, load reversal, fatigue).
• Scope: Bolt strength only; estimates/reference values and not a substitute for complete connection design.

Worked example

Bolt hole sizing

Standard structural hole sizes per Steel Construction Manual Table J3.3.

• 1/4" to 7/8", Standard hole = d + 1/16 in. Example: 3/4 in bolt → 13/16 in hole.
• 1" and larger, Standard hole = d + 1/8 in. Example: 1 in bolt → 1-1/8 in hole.
• Oversized & slotted, Permitted only where allowed by AISC/RCSC. Increased hole clearance can affect slip, bearing, tearout, net section and edge-distance requirements. Additional detailing and installation requirements may apply.

Bolt length selection

Length ≈ Grip + Washers + Nut + Stick-through; Length = Unthreaded length + Threaded length.

• Grip (g), total thickness of connected material.
• Washer thickness (wt), thickness of each washer in the stack.
• Nut thickness (nt), thickness of the nut.
• Stick-through (st), bolt end past the nut after tightening.
• Length (L), overall bolt length.
• Unthreaded length (Lun), shank length, threads excluded.
• Threaded length (Lt), length of the threaded portion.
• Bolt diameter (d), nominal shank diameter.
• Hole diameter (dh), diameter of the hole the bolt passes through.

Field notes

• Spacing & edge distance. Spacing: 2-2/3 d minimum (J3.3); 3 d typical for detailing. Verify minimum edge distance using AISC Table J3.4.
• Application may govern over bolt capacity. Bolt capacity does not govern the connection. Check the surrounding material and connection geometry for bearing, tearout, block shear and net section.
• Double shear. Double shear increases shear strength, not tension. Count the shear planes, not the plies.
• Threads in shear plane. Values shown are based on threads included in the shear plane (N). Threads excluded (X) may provide increased shear strength where permitted by the connection detail; use the applicable AISC value.
• A490 coating. A490 is not hot-dip galvanized. Qualified alternative coatings exist; verify against ASTM F3125 / RCSC.
• A449 applications. A449 is not permitted in slip-critical joints and is not a substitute for F3125 A325/A490. Verify applicability where larger-diameter bolts are required. F1554 governs anchor rods.

References

Primary references: ANSI/AISC 360-22; AISC Steel Construction Manual, 16th Ed.; RCSC Specification for Structural Joints Using High-Strength Bolts (2020); ASTM F3125/F3125M; ASTM A449; SAE J429; ISO 898-1.