Bolt Pattern Calculator — mm, kN
How to use this calculator
Choose a bolt pattern layout (circular or rectangular), select bolt size (M12–M30), grade, and connection type. The calculator computes individual bolt capacity and total pattern capacity in shear and tension per EN 1993-1-8. Results update instantly with an SVG plan view.
Grades — 8.8 (fub=800 MPa) and 10.9 (fub=1000 MPa).
Connection type — Bearing (Category A/D), slip-critical (Category B/C, μ=0.4), or tension (Category D/E).
Saved Calculations
| Time | Pattern | Bolts | Grade | Shear kN | Tension kN | Cost |
|---|
How to Calculate Bolt Pattern Capacity (Eurocode)
This calculator determines shear and tension resistance of bolt groups per EN 1993-1-8. Select the bolt size (M12–M30), property class (8.8 or 10.9), connection category, and pattern layout. The calculator uses tensile stress area As and partial safety factor γM2=1.25 for resistance calculations.
Formulas
Shear (through threads): Fv,Rd = 0.6 × fub × As / γM2. Shear (through shank): Fv,Rd = 0.6 × fub × A / γM2. Tension: Ft,Rd = 0.9 × fub × As / γM2. Slip-critical: Fs,Rd = ks × n × μ × Fp,C / γM3, where Fp,C = 0.7 × fub × As.
FAQ
What tensile stress area is used? The calculator uses standard tensile stress areas per ISO 898-1: M12=84.3, M16=157, M20=245, M22=303, M24=353, M27=459, M30=561 mm².
What is the difference between categories? Category A: bearing in shear. Category B: slip-critical at serviceability. Category C: slip-critical at ULS. Category D: tension (non-preloaded). Category E: tension (preloaded).
