Belt Tension Calculator

Inputs

Power transmitted (P)

Power carried by the belt at the drive pulley.

Belt speed (v)

Belt (surface) speed — π · D · n for the drive pulley.

m/s

Wrap angle (θ)

Angle of belt contact on the smaller pulley.

Friction coefficient (μ)

Belt–pulley friction; ~0.3 rubber on steel, higher for V-grooves (use effective μ).

Default result

Effective tension(Te)

500N

Pass

112.4 lbf

Net tension that transmits the power.

Net tension that transmits the power: Te = P / v.

Also computed

Tight-side tension(T₁)819.2N

184.2 lbf

Te · e^μθ / (e^μθ − 1).

Slack-side tension(T₂)319.2N

71.76 lbf

Slack side stays in tension — good grip margin.

Te / (e^μθ − 1) — must stay positive or the belt slips.

Method notes 4 notes

The power is carried by the effective (net) tension Te = P / v — the difference between the tight and slack sides.
The capstan (Euler) equation limits the strand ratio before slip: T₁ / T₂ = e^(μθ) = 2.566 for these inputs (θ in radians).
Slack-side tension T₂ must stay positive — if it reaches zero the belt slips. More wrap angle, more friction, or a higher belt speed all raise the margin.
V-belts grip far better than flat belts: the groove wedges the belt, so use an effective μ (μ / sin(½·groove angle)), which is several times the flat-belt value.