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Fuel Mass Ratio Calculator

Work out fuel mass ratio instantly with clear inputs, formula shown and shareable results.

About Fuel Mass Ratio Calculator

Rearranging Tsiolkovsky gives the mass ratio as e^(dv/ve). Reaching orbit's 9400 m/s on a 340 s engine needs a ratio of 16.6, so a 25 tonne dry stage requires 390 tonnes of propellant - 94% of lift-off mass. That is why single-stage-to-orbit is so hard and why launchers stage.

Formulas

Mass ratio

m0 / mf = e^(dv / ve), with ve = Isp x g0

Propellant mass

propellant = dry mass x (mass ratio - 1)

Worked example

With the default values below, Fuel Mass Ratio Calculator returns Required Mass Ratio of 16.7637. Change any input above and every figure here is recalculated in your browser.

Inputs used

Delta-V requiredminimum 0 m/s
9,400 m/s
Specific impulseminimum 0 s
340 s
Dry mass including payloadminimum 0 kg
25,000 kg

Results

Required Mass Ratio
16.7637
Propellant Needed
394,092 kg
Total Vehicle Mass
419,092 kg
Propellant As A Share Of Total Mass
94.03%

Step by step

  1. 1Values used
  2. 2Mass ratio
  3. 3Propellant mass
  4. 4Required Mass Ratio= 16.7637
  5. 5Propellant Needed= 394,092 kg
  6. 6Total Vehicle Mass= 419,092 kg
  7. 7Propellant As A Share Of Total Mass= 94.03

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does staging help?

Because discarding empty tanks removes dead mass, so later stages get a favourable ratio without carrying spent structure.

How does a higher Isp reduce propellant?

Exponentially. Raising Isp from 340 to 450 s cuts the required ratio from 16.6 to about 8.3 for the same delta-v.

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Fuel Mass Ratio Calculator – Calculate Required Mass Ratio