Tension Calculator
Works out the pull in a rope for common setups.
Tension in each rope
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Acceleration — m/s²
Weight of the load —
Reading this —
The formula
one rope: T = m(g + a) two ropes: T = mg ÷ (2 cos θ) Atwood: a = (m₁ − m₂)g ÷ (m₁ + m₂), T = 2m₁m₂g ÷ (m₁ + m₂)
Tension is what balances the load, plus whatever is needed to accelerate it.
What to watch out for
This is a physics result, not a rating. Lifting gear needs its own safety factors and certification.
Frequently Asked Questions
Why does tension rise as ropes spread apart?
Only the vertical part of the pull holds the load up. A 10 kg load on two ropes has 49 N in each when vertical and 98.1 N in each at 60° from vertical.
What is the tension with 10 kg and 6 kg over a pulley?
73.55 N, with an acceleration of 2.45 m/s².