M20 Bolt Size and Thread Specifications

Q: What is the standard pitch for an M20 bolt?

The standard coarse pitch for M20 is 2.5 mm. Fine pitch is often 1.5 mm or 2.0 mm mm where specified.

Q: What imperial fastener is closest to M20?

3/4-10 is a practical imperial reference for M20; always verify against your application.

What is an M20 bolt?

An M20 bolt has 20 mm nominal diameter with 2.5 mm coarse pitch in common ISO listings. Large structural bolts may use different pitches per project standards.

M20 is standard in steel construction and large machines for anchor-style and high-strength joints. Match structural specifications for grade and torque. Spanish reference: perno M20.

Specifications

Specification	Value
Nominal diameter	20 mm
Standard pitch (coarse)	2.5 mm
Fine pitch	1.5 mm or 2.0 mm
Tap drill size	17.5 mm
Closest imperial equivalent	3/4-10

Hex head size

Bolt size	Hex head size
M20	30 mm

Common uses

Steel structures, machinery bases, medium anchor bolts, and heavy assemblies.

Related tools

Metric to Imperial Screw Converter — compare M20 to common inch threads.
Tap Drill Calculator — tap drill size for M20 and other metric threads.
Thread Identifier Tool — match measured diameter and pitch to a standard.

Related charts

Universal Screw & Bolt Size Chart — metric, imperial, pitch, and tap drill in one view.
Tap Drill Chart — metric tap drill sizes.

FAQ

What is the standard pitch for an M20 bolt?

The common coarse pitch for M20 is 2.5 mm. Fine pitch options include 1.5 mm or 2.0 mm where specified.

What drill size should be used for tapping M20 threads?

For M20 x 2.5 coarse thread, use approximately a 17.5 mm tap drill. Use our Tap Drill Calculator for other pitches.

What imperial fastener is closest to M20?

3/4-10 is a practical reference for comparing M20 to inch hardware; verify fit for your application.

Related guide

Metric vs Imperial Fasteners