Screw & Pipe Thread Charts

Free dimensional reference tables for the thread standards used every day in mechanical design: pitch, diameters and tap drill sizes, straight from ISO and ASME basic dimensions.

Not every thread is metric, and not every pipe thread seals the same way. This page collects the six thread standards engineers look up most often — pick the one you need, or use it to confirm which family a thread belongs to before you order a fitting or cut a tap.

M1 – M68

ISO Metric Coarse Thread Chart

The default general-purpose metric fastener thread (ISO 724). Pitch, diameters and tap drill sizes.

Open chart → M6×0.75 – M64×4

ISO Metric Fine Thread Chart

Fine-pitch metric variants for higher stress area, precision adjustment and thin-walled parts.

Open chart → #2-56 – 4"-4

UNC Thread Chart

Unified National Coarse (ASME B1.1) — the standard US/imperial general-purpose fastener thread.

Open chart → #0-80 – 1½"-12

UNF Thread Chart

Unified National Fine (ASME B1.1) — higher strength and finer adjustment for the same diameter.

Open chart → G 1/16 – G 6

BSP Thread Chart

British Standard Pipe, parallel (BSPP/G, ISO 228-1) — the standard pipe thread outside North America.

Open chart → 1/16" – 6"

NPT Thread Chart

National Pipe Taper (ASME B1.20.1) — the standard tapered pipe thread in North America.

Open chart →

Which thread standard do I have?

It's marked with an "M" and a number, e.g. M8 or M8×1
ISO metric — if the pitch is omitted, the coarse pitch is implied. An explicitly stated pitch (like the "×1" in M8×1) can be either coarse or fine — check it against the coarse or fine chart.
It's marked with a fraction or a "#" and two numbers, e.g. 3/8-16 or #10-32
Unified inch thread — UNC (coarse) or UNF (fine), common on US-made equipment.
It's a pipe/fitting thread marked "G", e.g. G 1/2
BSP parallel (BSPP) — seals on a flat face or O-ring, not on the thread itself.
It's a pipe/fitting thread with no letter, just a fraction, e.g. 1/2" NPT
Very likely NPT — tapered, seals by thread interference with tape or sealant. Common on North American equipment; do not force it into a BSP port.

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