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 systems

10 systems · 210 designations
ISO MetricMETRIC · ISO 26182 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

All METRIC
M1 × 0.25M1.2 × 0.25M1.4 × 0.3M1.6 × 0.35M1.8 × 0.35M2 × 0.4M2.2 × 0.45M2.5 × 0.45M3 × 0.5M3.5 × 0.6M4 × 0.7M4.5 × 0.75M5 × 0.8M5.5 × 0.9M6 × 1M7 × 1M8 × 1.25M9 × 1.25M10 × 1.5M11 × 1.5M12 × 1.75M14 × 2M16 × 2M18 × 2.5M20 × 2.5M22 × 2.5M24 × 3M27 × 3M30 × 3.5M33 × 3.5M36 × 4M39 × 4M42 × 4.5M45 × 4.5M48 × 5M52 × 5M56 × 5.5M60 × 5.5M64 × 6M1 × 0.2 fineM1.2 × 0.2 fineM1.4 × 0.2 fineM1.6 × 0.2 fineM1.8 × 0.2 fineM2 × 0.25 fineM2.5 × 0.35 fineM3 × 0.35 fineM3.5 × 0.35 fineM4 × 0.5 fineM4.5 × 0.5 fineM5 × 0.5 fineM6 × 0.75 fineM7 × 0.75 fineM8 × 1 fineM8 × 0.75 fineM9 × 1 fineM10 × 1.25 fineM10 × 1 fineM11 × 1 fineM12 × 1.5 fineM12 × 1.25 fineM14 × 1.5 fineM16 × 1.5 fineM18 × 2 fineM18 × 1.5 fineM20 × 2 fineM20 × 1.5 fineM22 × 2 fineM22 × 1.5 fineM24 × 2 fineM27 × 2 fineM30 × 2 fineM33 × 3 fineM36 × 3 fineM39 × 3 fineM42 × 3 fineM45 × 3 fineM48 × 3 fineM52 × 4 fineM56 × 4 fineM60 × 4 fineM64 × 4 fine

Unified National Coarse25 designations · ASME B1.1

All UNC
#1-64 UNC#2-56 UNC#3-48 UNC#4-40 UNC#5-40 UNC#6-32 UNC#8-32 UNC#10-24 UNC#12-24 UNC1/4-20 UNC5/16-18 UNC3/8-16 UNC7/16-14 UNC1/2-13 UNC9/16-12 UNC5/8-11 UNC3/4-10 UNC7/8-9 UNC1-8 UNC1-1/8-7 UNC1-1/4-7 UNC1-3/8-6 UNC1-1/2-6 UNC1-3/4-5 UNC2 UNC

Unified National Fine23 designations · ASME B1.1

All UNF
#0-80 UNF#1-72 UNF#2-64 UNF#3-56 UNF#4-48 UNF#5-44 UNF#6-40 UNF#8-36 UNF#10-32 UNF#12-28 UNF1/4-28 UNF5/16-24 UNF3/8-24 UNF7/16-20 UNF1/2-20 UNF9/16-18 UNF5/8-18 UNF3/4-16 UNF7/8-14 UNF1-12 UNF1-1/8-12 UNF1-1/4-12 UNF1-1/2-12 UNF

Unified National Extra Fine9 designations · ASME B1.1

All UNEF
1/4-32 UNEF5/16-32 UNEF3/8-32 UNEF7/16-28 UNEF1/2-28 UNEF9/16-24 UNEF5/8-24 UNEF3/4-20 UNEF7/8-20 UNEF

National Pipe Taper14 designations · ASME B1.20.1

All NPT
1/16-27 NPT taper1/8-27 NPT taper1/4-18 NPT taper3/8-18 NPT taper1/2-14 NPT taper3/4-14 NPT taper1-11.5 NPT taper1-1/4-11.5 NPT taper1-1/2-11.5 NPT taper2-11.5 NPT taper2-1/2-8 NPT taper3-8 NPT taper3-1/2-8 NPT taper4-8 NPT taper

National Pipe Straight11 designations · ASME B1.20.1

All NPS
1/8-27 NPS1/4-18 NPS3/8-18 NPS1/2-14 NPS3/4-14 NPS1-11.5 NPS1-1/4-11.5 NPS1-1/2-11.5 NPS2-11.5 NPS2-1/2-8 NPS3-8 NPS

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

All BSP
1/8-28 BSP1/4-19 BSP3/8-19 BSP1/2-14 BSP5/8-14 BSP3/4-14 BSP7/8-14 BSP1-11 BSP1-1/4-11 BSP1-1/2-11 BSP2-11 BSP

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

All BSPT
1/8-28 BSPT taper1/4-19 BSPT taper3/8-19 BSPT taper1/2-14 BSPT taper3/4-14 BSPT taper1-11 BSPT taper1-1/4-11 BSPT taper1-1/2-11 BSPT taper2-11 BSPT taper

Trapezoidal16 designations · ISO 2901

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

ACME10 designations · ASME B1.5

All ACME
1/4-16 ACME5/16-14 ACME3/8-12 ACME1/2-10 ACME5/8-8 ACME3/4-6 ACME1-5 ACME1-1/4-5 ACME1-1/2-4 ACME2-4 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.