How do I calculate timing belt length in teeth?

Belt length L = 2C + π(d1+d2)/2 + (d2−d1)²/(4C) where d = z×p/π (pitch diameter from teeth×pitch). Number of belt teeth = L/pitch, rounded to nearest standard belt size.

What is the difference between HTD and GT profiles?

HTD (High Torque Drive) uses a curvilinear tooth profile. GT (Gates Tooth, e.g., GT2, GT3, GT5) is an improved profile with a modified curvilinear shape, providing better load distribution, reduced backlash, and higher power capacity than HTD.

How do I select the right timing belt pitch?

Pitch selection depends on power and speed: GT2 (2mm) for light duty/3D printers, HTD-3M/GT3 for small drives up to ~5kW, HTD-5M/GT5 for medium 2-30 kW, HTD-8M for 10-100 kW, HTD-14M for 50-250+ kW.

What is the minimum number of teeth on a timing pulley?

Minimum pulley teeth depend on pitch: GT2/3M: 12 teeth, 5M: 14 teeth, 8M: 22 teeth, 14M: 28 teeth. Using fewer teeth increases belt bending stress and reduces belt life.

Can I adjust center distance for timing belts?

Timing belts are not elastic like V-belts, so center distance must match the belt length exactly. Use a tensioner idler or select pulleys and belt length that give the desired center distance. Belt manufacturers provide tables of standard belt lengths.

Free Engineering Tool #089

Timing Belt Calculator

Calculate timing belt length in pitches and number of teeth. Supports HTD 3/5/8/14 and GT2/GT3/GT5 profiles. Enter pulley teeth, center distance, and pitch.

HTD 3/5/8/14 GT2/GT3/GT5 Synchronous

Results

Belt Length (Number of Teeth)

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Belt Length (mm)

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Drive Ratio

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Pitch Diameters (d₁ / d₂)

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Actual Center Distance

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Pitch Diameter

Belt Length (Number of Teeth)

Timing Belt Pitch Selection

Pitch	Profile	Power Range	Min Pulley Teeth
2 mm	GT2	Light duty, 3D printers	12
3 mm	HTD-3M / GT3	Up to 5 kW	12
5 mm	HTD-5M / GT5	2 – 30 kW	14
8 mm	HTD-8M	10 – 100 kW	22
14 mm	HTD-14M	50 – 250+ kW	28

Example — HTD-5M Belt

Given: z₁=20, z₂=60, pitch=5 mm, C=200 mm

d₁ = 20×5/π = 31.83 mm, d₂ = 60×5/π = 95.49 mm

L_mm = 2×200 + π(31.83+95.49)/2 + (95.49-31.83)²/(4×200) = 606.3 mm

Belt teeth = 606.3/5 = 121.3 → 122 teeth (610 mm belt)

Timing Belt Calculator | HTD, GT2, GT3 | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Pitch Diameter

Belt Length (Number of Teeth)

Timing Belt Pitch Selection