Standard bolt sizes and thread specifications

Standard Bolt Sizes

Metric M-series and imperial UNC/UNF bolt dimensions, thread geometry calculations, tensile stress areas, and property class strength values for bolted joint design.

Standard Bolt Sizes – Metric & Imperial Thread Data

Complete metric M-series and imperial UNC/UNF bolt specifications: thread pitch, major/minor/pitch diameters, tensile stress area, and property class strength values.

Bolt Specification Standards

Bolted joints are the most common mechanical fastener in engineering. Correct specification requires knowing the nominal diameter, thread pitch, stress area for load calculation, and the strength grade (property class for metric, grade for imperial). Metric bolts follow ISO 261/262 with M-series diameters from M1.6 to M100. Imperial bolts follow ASME B1.1 (UNC coarse) and B1.3 (UNF fine) standards.

Calculators Available:
  • 🔩 Metric Bolt Sizes (M-Series) – ISO standard dimensions: nominal diameter, pitch, major/minor diameter, tensile stress area.
  • 🔧 UNC/UNF Thread Sizes – Imperial coarse and fine thread geometry from 0-80 to 1½-6 UNC.
  • 💪 Bolt Strength Grades – Property class (4.6, 8.8, 10.9, 12.9) yield and ultimate strength values; grade 2/5/8 imperial equivalents.
  • 📐 Thread Geometry Calculator – Compute pitch diameter, minor diameter, helix angle, and thread engagement length for any specification.
Metric Bolt Calculator (ISO 261)

Select an ISO metric bolt (M1.6–M100) to compute pitch diameter d₂, minor diameter d₁, and tensile stress area Aₛ using ISO thread geometry formulas.