M13 Bolt Size and Thread Specifications

The standard coarse pitch for M13 is 1.75 mm. Fine pitch is often 1.5 mm where specified.

1/2-13 (approx.) is a practical imperial reference for M13; always verify against your application.

What is an M13 bolt?

An M13 bolt has 13 mm nominal diameter with typical coarse pitch 1.75 mm. It is a specialty size—verify taps, dies, and mating hardware.

M13 is uncommon compared with M12 or M14. Treat manufacturer drawings as authoritative for pitch and strength. Spanish reference: perno M13.

Specification	Value
Nominal diameter	13 mm
Standard pitch (coarse)	1.75 mm
Fine pitch	1.5 mm
Tap drill size	11.2 mm
Closest imperial equivalent	1/2-13 (approx.)

Bolt size	Hex head size
M13	20 mm

Equipment that explicitly lists M13 in service documentation.

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

The common coarse pitch for M13 is 1.75 mm. Fine pitch is often 1.5 mm where specified.

For M13 x 1.75 coarse thread, use approximately a 11.2 mm tap drill. Use our Tap Drill Calculator for other pitches.

1/2-13 (approx.) is a practical reference for comparing M13 to inch hardware; verify fit for your application.