Thread Database

Pitch, major and minor diameters, TPI and tap drill size for 210 thread designations across 10 thread systems. Every figure is either derived from the standard’s basic profile or taken from its tables — each page says which.

Thread systems10 systems · 210 sizes · metric and inch (imperial)

ISO MetricMETRIC · ISO 261 & ISO 26282 sizesflank 60°Unified National CoarseUNC · ASME B1.125 sizesflank 60°Unified National FineUNF · ASME B1.123 sizesflank 60°Unified National Extra FineUNEF · ASME B1.19 sizesflank 60°National Pipe TaperNPT · ASME B1.20.114 sizesflank 60°National Pipe StraightNPS · ASME B1.20.111 sizesflank 60°British Standard Pipe (parallel)BSP · ISO 228-111 sizesflank 55°British Standard Pipe (taper)BSPT · ISO 7-19 sizesflank 55°TrapezoidalTR · ISO 290116 sizesflank 30°ACMEACME · ASME B1.510 sizesflank 29°

ISO Metric82 designations · ISO 261 & ISO 262

M1 × 0.25 M1 × 0.2 fine M1.2 × 0.25 M1.2 × 0.2 fine M1.4 × 0.3 M1.4 × 0.2 fine M1.6 × 0.35 M1.6 × 0.2 fine M1.8 × 0.35 M1.8 × 0.2 fine M2 × 0.4 M2 × 0.25 fine M2.2 × 0.45 M2.5 × 0.45 M2.5 × 0.35 fine M3 × 0.5 M3 × 0.35 fine M3.5 × 0.6 M3.5 × 0.35 fine M4 × 0.7 M4 × 0.5 fine M4.5 × 0.75 M4.5 × 0.5 fine M5 × 0.8 M5 × 0.5 fine M5.5 × 0.9 M6 × 1 M6 × 0.75 fine M7 × 1 M7 × 0.75 fine M8 × 1.25 M8 × 1 fine M8 × 0.75 fine M9 × 1.25 M9 × 1 fine M10 × 1.5 M10 × 1.25 fine M10 × 1 fine M11 × 1.5 M11 × 1 fine M12 × 1.75 M12 × 1.5 fine M12 × 1.25 fine M14 × 2 M14 × 1.5 fine M16 × 2 M16 × 1.5 fine M18 × 2.5 M18 × 2 fine M18 × 1.5 fine M20 × 2.5 M20 × 2 fine M20 × 1.5 fine M22 × 2.5 M22 × 2 fine M22 × 1.5 fine M24 × 3 M24 × 2 fine M27 × 3 M27 × 2 fine M30 × 3.5 M30 × 2 fine M33 × 3.5 M33 × 3 fine M36 × 4 M36 × 3 fine M39 × 4 M39 × 3 fine M42 × 4.5 M42 × 3 fine M45 × 4.5 M45 × 3 fine M48 × 5 M48 × 3 fine M52 × 5 M52 × 4 fine M56 × 5.5 M56 × 4 fine M60 × 5.5 M60 × 4 fine M64 × 6 M64 × 4 fine

Unified National Coarse (UNC)25 designations · ASME B1.1

Unified National Fine (UNF)23 designations · ASME B1.1

Unified National Extra Fine (UNEF)9 designations · ASME B1.1

1/4-32 UNEF 5/16-32 UNEF 3/8-32 UNEF 7/16-28 UNEF 1/2-28 UNEF 9/16-24 UNEF 5/8-24 UNEF 3/4-20 UNEF 7/8-20 UNEF

National Pipe Taper (NPT)14 designations · ASME B1.20.1

1/16-27 NPT taper 1/8-27 NPT taper 1/4-18 NPT taper 3/8-18 NPT taper 1/2-14 NPT taper 3/4-14 NPT taper 1-11.5 NPT taper 1-1/4-11.5 NPT taper 1-1/2-11.5 NPT taper 2-11.5 NPT taper 2-1/2-8 NPT taper 3-8 NPT taper 3-1/2-8 NPT taper 4-8 NPT taper

National Pipe Straight (NPS)11 designations · ASME B1.20.1

1/8-27 NPS 1/4-18 NPS 3/8-18 NPS 1/2-14 NPS 3/4-14 NPS 1-11.5 NPS 1-1/4-11.5 NPS 1-1/2-11.5 NPS 2-11.5 NPS 2-1/2-8 NPS 3-8 NPS

British Standard Pipe (parallel) (BSP)11 designations · ISO 228-1

1/8-28 BSP 1/4-19 BSP 3/8-19 BSP 1/2-14 BSP 5/8-14 BSP 3/4-14 BSP 7/8-14 BSP 1-11 BSP 1-1/4-11 BSP 1-1/2-11 BSP 2-11 BSP

British Standard Pipe (taper) (BSPT)9 designations · ISO 7-1

1/8-28 BSPT taper 1/4-19 BSPT taper 3/8-19 BSPT taper 1/2-14 BSPT taper 3/4-14 BSPT taper 1-11 BSPT taper 1-1/4-11 BSPT taper 1-1/2-11 BSPT taper 2-11 BSPT taper

Trapezoidal (TR)16 designations · ISO 2901

Tr8 × 1.5 Tr10 × 2 Tr10 × 1.5 Tr12 × 3 Tr12 × 2 Tr14 × 3 Tr16 × 4 Tr16 × 2 Tr18 × 4 Tr20 × 4 Tr24 × 5 Tr24 × 3 Tr28 × 5 Tr30 × 6 Tr36 × 6 Tr40 × 7

ACME10 designations · ASME B1.5

1/4-16 ACME 5/16-14 ACME 3/8-12 ACME 1/2-10 ACME 5/8-8 ACME 3/4-6 ACME 1-5 ACME 1-1/4-5 ACME 1-1/2-4 ACME 2-4 ACME

Where these numbers come from

Thread dimensions are not measured, they are defined. For metric, unified and Whitworth forms the numbers on each page are computed from the standard’s basic profile — the fundamental triangle and the truncations at crest and root — so anyone can recompute them from the pitch. Pipe threads are the exception: a pipe size is a nominal bore rather than a diameter (1/8 NPT measures 0.405 in across the thread), so those values are tabulated from the standard instead. Each page states which of the two applies.