Timing Belt Size Chart

Identify the Pitch First

The pitch is the distance between adjacent tooth centers — the single number that decides everything. Measure it with a caliper between two teeth, or read it from the belt marking.

Pitch	Profile	Typical Widths	Common Uses
2 mm	GT2 / 2GT	6, 9, 10, 15 mm	3D printers, CNC, laser cutters
3 mm	3GT / GT3	6, 9, 10, 15 mm	Heavier gantries, medium CNC
5 mm	HTD 5M	6, 9, 15, 20, 25, 30 mm	Actuators, small conveyors
8 mm	HTD 8M	9, 15, 20, 30, 50, 85 mm	Packaging, power transmission
14 mm	HTD 14M	20, 30, 40, 50, 85 mm	Heavy industrial drives
5 mm	T5 (trapezoidal)	10, 15, 20, 25 mm	Legacy metric drives
10 mm	T10 / AT10	16, 25, 32, 50 mm	Legacy metric drives
2.032 mm	MXL (imperial)	3.2, 4.8, 6.4 mm	Instruments, legacy
5.08 mm	XL (imperial)	6.4, 9.5, 12.7 mm	Legacy light drives
9.525 mm	L (imperial)	12.7, 19.1, 25.4 mm	Legacy medium drives
12.7 mm	H (imperial)	25.4, 38.1, 50.8 mm	Legacy heavy drives

Measure pitch between tooth centers, not tooth edges. A caliper reading between the same points on two adjacent teeth gives the pitch.

Endless Belt Lengths (Standard Ranges)

Endless belt length = number of teeth × pitch. Common stock ranges:

Profile	Typical Length Range	Teeth Range
GT2 (2 mm)	100 - 500 mm (open-ended usually)	50 - 250 teeth
HTD 5M	375 - 1,500 mm	75 - 300 teeth
HTD 8M	480 - 4,400 mm	60 - 550 teeth
HTD 14M	966 - 4,760 mm	69 - 340 teeth

Reading a Belt Part Number

Most manufacturers mark belts with the size:

HTD 8M 1000-20 → HTD profile, 8 mm pitch, 1000 mm length, 20 mm wide
GT2 6mm → GT2 profile, 6 mm wide (open-ended, length separate)
T10 1500-25 → trapezoidal T10, 1500 mm length, 25 mm wide
XL 037 → imperial XL profile, 0.375 inch width

If the marking is worn, measure: pitch (caliper), width (ruler), length (tape around the outside, or count teeth × pitch).

Belt Length Calculation

For a two-pulley drive:

Belt length = 2C + π(D1 + D2)/2 + (D2 - D1)²/(4C)

Where C = center distance, D1/D2 = pulley pitch diameters.

Then round up to the nearest whole number of teeth (length must be teeth × pitch). For open-ended belts, measure the run with margin for the tensioner.

Width vs Load (Quick Guide)

At the same pitch, torque capacity scales roughly with width:

Profile	Light Load	Medium Load	Heavy Load
GT2	6 mm	9-10 mm	15 mm
HTD 5M	9 mm	15-20 mm	25-30 mm
HTD 8M	15 mm	20-30 mm	50 mm
HTD 14M	20-30 mm	40-50 mm	85 mm

Still Unsure?

Send us a photo of the old belt with a ruler, or the part number — we will identify the pitch, width, and length and quote the replacement.

How to Choose a Timing Belt
Timing Belts 101
Timing Pulleys [How to Choose a Timing Belt] [Timing Belts 101] [Timing Belt FAQ] [Request a Quote]