⚙️ Belt Length Calculator
Calculate the length of belt needed to connect two pulleys of given diameters at a set center distance.
mm
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mm
What this calculates
When designing a belt-and-pulley system, you need to know the correct belt length so the belt fits snugly around both pulleys with the chosen center distance.
The formula
For an open (crossed-free) belt drive, the standard approximation is: L = 2C + (π/2)(D1 + D2) + (D2 – D1)² / (4C), where C is the center-to-center distance and D1, D2 are the pulley diameters. This calculator uses radii internally but the result is equivalent.
This gives a close engineering estimate; always verify against manufacturer belt-length charts for the exact belt type and size you plan to purchase.
Last reviewed August 2026