Conveyor Belt Tension Calculator

Lift height feeds into the gravity component of effective tension as materialPerMeter × g × liftHeight, and the calculator takes the absolute value of the total effective tension before computing tight-side tension. Entering a negative value (a decline) means the material's weight assists the belt's motion instead of resisting it, so the gravity term subtracts from the friction term — on a steep enough decline this can reduce effective tension toward zero or even flip which pulley needs to be the drive.

Tight-side tension is effective tension multiplied by the wrap factor, T1 = Te × e^(μθ)/(e^(μθ) − 1), derived from Euler's belt-friction equation. With μ fixed at 0.35 for a lagged pulley, that multiplier grows as wrap angle θ increases — a 210° single-pulley wrap gives a smaller factor than a 360–420° dual-pulley wrap, which is exactly why dual-drive arrangements let you transmit more tension without belt slip for the same effective tension.

The calculator computes both the tight-side tension (T1, from the drive traction requirement) and a separate minimum sag tension (from keeping belt sag under 2% of your idler spacing), then reports whichever is larger as the governing tension. On long runs with high idler spacing or light loads, sag tension can exceed T1 — meaning the belt needs to be tensioned tighter than the drive alone requires, purely to keep it from sagging excessively between supports.

μ = 0.35 is hard-coded in this calculator as a typical value for a lagged (rubber-covered) drive pulley in normal, dry conditions — it isn't one of the exposed inputs. A bare steel pulley or a wet/oily belt surface would have a meaningfully different real-world friction coefficient, so if your drive pulley isn't lagged or runs in wet conditions, treat the tight-side tension and safety factor here as optimistic and consult drive-specific traction data.

Counterweight mass is (2 × max(slack-side tension, sag tension)) / g, doubling whichever of the two governing tensions is larger before converting from force to mass. The factor of two accounts for the fact that a gravity takeup pulley is typically wrapped by both the outgoing and returning belt strands, so the counterweight must supply twice the required tension to the belt loop through the pulley.