How this calculator works
Weight is a force equal to mass times local gravity. Dividing total thrust by that force gives a dimensionless ratio. For a vertical vehicle with aligned thrust and no drag, a ratio greater than one permits upward acceleration. Comparison mode uses the same local gravity for both vehicles. Supply thrust and mass for the conditions you want to compare; fuel loading, altitude and throttle change published values.
Formula
TWR = F/(mg). F = TWR mg; m = F/(TWR g); g = F/(TWR m). Ideal vertical acceleration = F/m-g.
Worked example
At g = 10 m/s2, a 10 kg vehicle weighs 100 N. Thrust of 100 N gives TWR = 1. A required ratio of 2 with thrust 300 N corresponds to mass 15 kg.
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Frequently asked questions
Is mass in kilograms the same as weight?
No. Kilograms measure mass; weight here is in newtons.
Does a ratio above one guarantee flight?
No. Stability, thrust direction, drag, structural limits and control also matter.
Can I compare an engine and a complete aircraft?
You can compute both ratios, but they describe different mass boundaries and should be labelled accordingly.