Belt Length Calculator (2 pulley system)

How to compute values for a belt to wrap around a pully system.? For accurate belt length calculation, use the following tool with simple and advance level calculation option. In this post I will also explain you its usage guide to make you learn how to use this tool easily, providing to calculation examples, and its mathematical formula.

Belt Length Calculator

Enter three values to calculate the belt length.

Enter the diameter of the larger pulley.

Enter the diameter of the smaller pulley.

Enter the length between the pulleys.

The belt length will be calculated here.

Enter the diameters and lengths between the pulleys to calculate the total belt length.

The total belt length will be calculated here.

More Calculators

The Belt Length is the length of the belt that goes around two pulley in a system. In mechanical systems such as conveyors and engines, the belt needs to be properly fitted and functioned.

User Guide

Step	Action
Enter Diameter (Large Pulley)	Input diameter of the larger pulley (e.g., 10 cm).
Enter Diameter (Small Pulley)	Input diameter of the smaller pulley (e.g., 5 cm).
Enter Distance	Input the distance between pulleys (e.g., 20 cm).
Click Calculate	Get the belt length result.

Input Examples

Parameter	Basic Example Value	Advanced Example Value
Diameter of Larger Pulley	10 cm	12 cm
Diameter of Smaller Pulley	5 cm	6 cm
Distance Between Pulleys	20 cm	25 cm
Calculated Belt Length	63.86 cm	76.56 cm

Belt Length Formula

The belt length is calculated with:

 $\text{BL} = \frac{(DL + DS) \times \pi}{2} + (2 \times L) + \frac{(DL - DS)^2}{4 \times L}$

Variable	Description
BL	Belt Length
DL	Diameter of Larger Pulley
DS	Diameter of Smaller Pulley
L	Distance Between the Pulleys

Calculation Solved Examples

1. Basic Calculation Example

Step	Calculation
Large Pulley (DL)	10 cm
Small Pulley (DS)	5 cm
Distance (L)	20 cm
Part 1 Calculation	$\frac{(10 + 5) \times \pi}{2} = 23.55$ cm
Part 2 Calculation	$2 \times 20 = 40$ cm
Part 3 Calculation	$\frac{(10 – 5)^2}{4 \times 20} = 0.3125$ cm
Total Calculation	$23.55 + 40 + 0.3125 = 63.86$ cm

Answer: The belt length is 63.86 cm.

2. Advanced Calculation Example

Step	Calculation
Large Pulley (DL)	12 cm
Small Pulley (DS)	6 cm
Distance (L)	25 cm
Part 1 Calculation	$\frac{(12 + 6) \times \pi}{2} = 28.27$ cm
Part 2 Calculation	$2 \times 25 = 50$ cm
Part 3 Calculation	$\frac{(12 – 6)^2}{4 \times 25} = 0.36$ cm
Total Calculation	$28.27 + 50 + 0.36 = 76.56$ cm

Answer: The belt length is 76.56 cm.

Belt Length Calculator (2 pulley system)