Thrust-to-Weight Ratio Calculator Formula

Understand the math behind the thrust-to-weight ratio calculator. Each variable explained with a worked example.

Use the Thrust-to-Weight Ratio Calculator

Formulas Used

Thrust-to-Weight Ratio

twr = thrust / (mass * gravity)

Net Vertical Acceleration

net_accel = thrust / mass - gravity

Variables

VariableDescriptionDefault
thrustThrust(N)7607000
massTotal Mass(kg)549054
gravitySurface Gravity(m/s2)9.80665

How It Works

Thrust-to-Weight Ratio

The TWR determines whether a vehicle can lift off and how quickly it accelerates.

Formula

TWR = F / (m * g)

  • *F* = engine thrust in newtons
  • *m* = total vehicle mass
  • *g* = local gravitational acceleration

    • TWR must exceed 1.0 for liftoff. Most launch vehicles aim for 1.2 to 1.8 at ignition.

    Worked Example

    Saturn V first stage: 7 607 000 N thrust, 549 054 kg.

    thrust = 7607000mass = 549054gravity = 9.80665
    1. 01TWR = F / (m * g)
    2. 02Weight = 549054 * 9.80665 = 5 384 000 N
    3. 03TWR = 7607000 / 5384000
    4. 04TWR = 1.413

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    Open Thrust-to-Weight Ratio Calculator