Free calculator, no sign-up
Belt length calculator: centre distance and span tension
Pitch length of a two-pulley belt from the centre distance, or the reverse, plus wrap angle, belt speed and span tension from its frequency. Free.
- Instant result
- Formula and standards shown
- On desktop and phone
Result
1,476.24mmPitch length
- Wrap angle
- 168.52°
- Ratio
- 2.000
- Output speed
- 725 rpm
- Belt speed
- 7.59 m/s
Free during the beta, no credit card
Belt length and tension written on the work order
Here, the calculator is free and the result is gone when you close the page. In Reglova, it is attached to the work order on the right machine: you find it again at the next breakdown, and on audit day.
The CMMS software comparison, our gaps included- Attached to the work order with its inputs: the server recalculates it, it stays verifiable.
- On the technician's phone, even without a network.
- In the machine's history, for the next breakdown.
- The result becomes a checklist step of the work order.
- The asset's nameplate data pre-fills the calculation.
When to calculate a belt length
01
Pick the replacement belt when the reference has worn off.
02
Find the installation centre distance before tensioning.
03
Check tension with a belt frequency meter rather than by thumb.
Good to know
Below 120° of wrap on the small pulley, the belt may slip. The mass per metre used for the tension comes from the belt manufacturer.
Belt length formula, wrap angle and span tension
For a two-pulley drive, the calculator gives the belt pitch length when the centre distance is known, or the centre distance when you start from a catalogue length. It also calculates the wrap angle on the small pulley, the ratio, the output speed and the belt speed, then the span tension from its vibration frequency.
Formula · Reference documents
L = 2C + π(D + d)/2 + (D − d)²/(4C) ; C = [b + √(b² − 8(D − d)²)]/8, b = 2L − π(D + d) ; β = 180° − 2·arcsin((D − d)/(2C)) ; T = 4·m·ℓ²·f²
ISO 4184, ISO 22 ; tension from the span frequency (Gates, Optibelt)
Inputs and accepted ranges
| Input | Unit | Accepted range | Example |
|---|---|---|---|
| Small pulley, pitch diameter d | mm | 10 to 3,000 | 100 mm |
| Large pulley, pitch diameter D | mm | 10 to 5,000 | 200 mm |
| Known value | 2 options | Centre distance | |
| Centre distanceif Known value: Centre distance | mm | 10 to 20,000 | 500 mm |
| Pitch lengthif Known value: Length | mm | 30 to 60,000 | |
| Small pulley speed | rpm | 1 to 100,000 | 1,450 rpm |
| Mass per metre | kg/m | 0.001 to 10 | Optional |
| Free span length | m | 0.01 to 20 | Optional |
| Span frequency | Hz | 1 to 1,000 | Optional |
Calculated results
- Pitch lengthmm
- Centre distancemm
- Wrap angle°
- Ratio
- Output speedrpm
- Belt speedm/s
- Span tensionN
What the calculator flags
- Wrap angle below 120°: risk of slipping.
- Over 30 m/s: beyond a classic V-belt.
Belt changes planned before the belt snaps
- Breakdowns reported by QR code
- Work orders on the phone, even without a network
- Mandatory inspections reminded by email
- Audit file as a PDF, in one click
Free during the beta, no credit card