Bolt Pattern Calculator — in, lbs
How to use this calculator
Choose a bolt pattern layout (circular or rectangular), enter bolt diameter, grade, and connection type. The calculator computes individual bolt capacity and total pattern capacity in shear and tension per AISC 360. Results update instantly with an SVG plan view.
Grades — A325 (Fnt=90 ksi, Fnv=54 ksi) and A490 (Fnt=113 ksi, Fnv=68 ksi).
Connection type — Bearing, slip-critical (Class A μ=0.35), or tension.
Saved Calculations
| Time | Pattern | Bolts | Grade | Shear kips | Tension kips | Cost |
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How to Calculate Bolt Pattern Capacity
This calculator determines the shear and tension capacity of bolt groups per AISC 360-22 (Specification for Structural Steel Buildings). Enter the bolt size, grade, connection type, and pattern layout. The calculator uses nominal bolt area and AISC design strengths with φ=0.75 for bearing and tension, φ=1.0 for slip-critical connections (Du=1.13, hf=1.0, Tb per Table J3.1).
Formulas
Bolt area: Ab = π/4 × d². Bearing shear: φRn = 0.75 × Fnv × Ab × ns. Tension: φRn = 0.75 × Fnt × Ab. Slip-critical: φRn = 1.0 × μ × Du × hf × Tb × ns. A325 Fnv(N)=54 ksi, Fnv(X)=68 ksi, Fnt=90 ksi. A490 Fnv(N)=68 ksi, Fnv(X)=84 ksi, Fnt=113 ksi.
FAQ
What is the difference between N-type and X-type? N-type assumes threads are in the shear plane (lower capacity). X-type assumes threads are excluded from the shear plane.
What is slip-critical? Slip-critical connections resist load through friction between faying surfaces. They are required when slip would cause serviceability issues or when bolts are in oversized/slotted holes.
