What is the name of the equation that relates rocket velocity to changing mass?

The Tsiolkovsky rocket equation relates a rocket’s change in velocity to its changing mass. It is commonly written as Δv = ve ln(m0/mf), where exhaust velocity, initial mass and final mass determine the ideal velocity change.

Konstantin Tsiolkovsky published the underlying idea in 1903. The equation explains why rockets carry propellant: as fuel and oxidizer are expelled, the vehicle becomes lighter, allowing the same engine performance to produce more acceleration. It also shows why carrying additional propellant becomes progressively less effective.

The equation is an idealized result. It assumes constant exhaust velocity and ignores atmospheric drag, gravity losses, steering losses and engine operation details. Engineers use it during mission design to estimate staging and propellant requirements. It is also called the ideal rocket equation, and it applies to rockets in space regardless of whether their propellant is chemical or another type.