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PHYSICS / ROCKET PROPULSION

Rocket Equation Delta-v Calculator

Calculate ideal rocket delta-v from effective exhaust velocity and the initial-to-final mass ratio.

  • 01 Calculated in this tab
  • 02 Values stay in this browser tab
  • 03 Use boundary

Conversion input

Known value

Filter by unit name, symbol, or code. Your current selections remain available.

Equation inputs

Preparing the calculator...

METHOD / WORKED EXAMPLE

Audit the mass ratio before using delta-v

The equation links propellant-driven mass change to an ideal velocity increment; it does not predict a complete trajectory or mission margin.

WORKED DEFAULT

Check the calculation with the default inputs

With 3,000 m/s effective exhaust velocity, 50,000 kg initial mass, and 20,000 kg final mass, the mass ratio is 2.5 and ideal delta-v is about 2,748.87 m/s.

  1. Form the mass ratio50,000 / 20,000 = 2.5
  2. Take the natural logarithmln(2.5) = 0.916291
  3. Apply exhaust velocity3,000 x 0.916291 = 2,748.87 m/s

READ THE RESULT

Interpret the output in context

Treat the output as an ideal propulsion budget. Real mission delta-v must also cover gravity, drag, steering, reserve, and performance losses established by the vehicle and trajectory design.

ASSUMPTIONS AND LIMITS

Know where the model stops

  • Initial and final mass describe the same burn.
  • Final mass is positive and smaller than initial mass.
  • Effective exhaust velocity stays constant during the modeled burn.

This ideal result excludes gravity loss, aerodynamic drag, steering loss, staging transients, changing exhaust performance, and reserve requirements.

Use internally consistent units and retain extra precision when carrying the result into another calculation.

OpenStax: rocket propulsion

COMMON QUESTIONS

Rocket Equation Delta-v Calculator FAQs

Is this delta-v the speed the rocket will reach?

No. Delta-v is a modeled change in velocity capacity, not a guaranteed final speed. The actual trajectory depends on starting velocity, gravity, atmospheric drag, steering, burn direction, staging, and timing. Mission analysis normally compares an ideal propulsion budget with a separately calculated required delta-v plus reserves.

Should propellant mass be entered as final mass?

No. Initial mass includes the vehicle, payload, and propellant before the modeled burn. Final mass is what remains after that burn, including dry structure, payload, residuals, and any unburned reserve. Entering propellant mass alone changes the mass ratio and produces the wrong result. Confirm both values against one burn state.

Can I model a multistage rocket in one calculation?

Not accurately as one ratio when stages have different exhaust velocities or discarded hardware. Calculate each stage or burn with its own initial mass, final mass, and effective exhaust velocity, then add the ideal delta-v increments. Keep staging losses and mission reserves as separate engineering allowances.

Use boundary

Calculation path

Apply the Tsiolkovsky rocket equation to one burn represented by a constant effective exhaust velocity. The page evaluates the displayed equation from your supplied values and presents both symbolic and substituted KaTeX working so the arithmetic can be checked.

Calculation path

Delta v = u ln(m0 / mf)