FlagshipTiming Belt Length Calculator
Belt length and centre distance
Work out the belt for your two pulleys
Pick the belt profile, enter both tooth counts and the centre distance. The belt length, nearest belts and wrap update as you type.
T
T
mm
Shaft centre to shaft centre
mm
The length printed on the belt, e.g. 752 for an 8M-752 belt
Units
Belt pitch length
750.6 mm 29.55 in · 93.8 teeth
- Speed ratio
- 2.00 : 1
- Pitch diameters
- 50.93 / 101.86 mm
- Wrap on small pulley
- 168.5°
- Teeth in mesh (small)
- 9
| Belt teeth | Pitch length | Centre distance |
|---|---|---|
| 93 T | 744.0 mm | 250.7 mm |
| 94 T | 752.0 mm | 254.7 mm |
Results are theoretical pitch lengths for an open, two-pulley drive. Check stock belt lengths with your belt supplier and allow centre adjustment for tensioning.
How it works
The formulas behind the calculator
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Pitch diameter
PD = teeth × pitch ÷ πThe belt runs on the pitch circle, so lengths are worked out from pitch diameters, not outside diameters.
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Belt length from centre distance
L = 2C + π(D + d) ÷ 2 + (D − d)² ÷ 4CC is the centre distance, D and d the large and small pitch diameters.
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Centre distance from belt length
C = (b + √(b² − 8(D − d)²)) ÷ 8, where b = 2L − π(D + d)Used for the nearest belts, and when you already have the belt.
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Wrap and teeth in mesh
θ = 180° − 2 × asin((D − d) ÷ 2C)Teeth in mesh = small pulley teeth × θ ÷ 360. Keep it at 6 or more.
Profiles
Belt profiles and pitches in the calculator
We machine timing pulleys for each of these profiles, in aluminium, steel, cast iron and plastics.
| Family | Profiles and pitch | Typical use |
|---|---|---|
| HTD | HTD 3M (3 mm), HTD 5M (5 mm), HTD 8M (8 mm), HTD 14M (14 mm), HTD 20M (20 mm) | High torque drives: machine tools, pumps, compressors, conveyors |
| STD (S-profile) | S3M (3 mm), S5M (5 mm), S8M (8 mm), S14M (14 mm) | Quiet, high torque drives; same pitches as HTD |
| GT | GT 2M (2 mm), GT 3M (3 mm), GT 5M (5 mm), GT 8M (8 mm), GT 14M (14 mm) | Precise positioning and low backlash: CNC, printing, packaging |
| Metric T | T2.5 (2.5 mm), T5 (5 mm), T10 (10 mm), T20 (20 mm) | Linear motion, packaging and printing machines |
| AT | AT3 (3 mm), AT5 (5 mm), AT10 (10 mm), AT20 (20 mm) | High-load linear drives and automation |
| Imperial | MXL (2.032 mm), XL (5.08 mm), L (9.525 mm), H (12.7 mm), XH (22.225 mm), XXH (31.75 mm) | General machinery, conveyors and older imported machines |
For your drive
Pulleys and bushes for the drive
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Flagship
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FAQ
Belt length questions
Work out each pulley's pitch diameter (teeth × pitch ÷ π), then belt length = 2C + π(D + d) ÷ 2 + (D − d)² ÷ 4C, where C is the centre distance. Divide the length by the pitch to get the number of belt teeth.
A timing belt has a whole number of teeth, so the exact length is rarely a stock belt. The calculator gives the belts just shorter and just longer, and the centre distance each one needs.
Aim for at least 6 teeth in mesh. With fewer, the belt can jump teeth under load, so use a bigger small pulley or longer centres.
Yes. Send the profile, tooth counts, bore and face width, or the numbers from this calculator, and we quote pulleys machined to suit.