Belt Tension Calculator

Inputs

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Power carried by the belt at the drive pulley.
kW
Belt (surface) speed — π · D · n for the drive pulley.
m/s
Angle of belt contact on the smaller pulley.
°
Belt–pulley friction; ~0.3 rubber on steel, higher for V-grooves (use effective μ).

Results

Default result
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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.

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