About this tool
The Rocket Delta-V Calculator is a free, in-browser spaceflight tool built on the Tsiolkovsky rocket equation, Δv = ve·ln(m₀/m_f), where m₀ is the wet (fully fuelled) mass, m_f is the dry (burnt-out) mass, and ve is the effective exhaust velocity. The exhaust velocity comes from the engine's specific impulse via ve = Isp·g₀, with the standard gravity g₀ = 9.80665 m/s². Delta-v is the fundamental currency of orbital mechanics — every manoeuvre has a delta-v cost.
All calculations run locally in your browser and nothing is uploaded, so your mission numbers stay on your device. Enter the specific impulse and any two of wet mass, dry mass, and delta-v, and the tool solves for the third. It also reports the mass ratio m₀/m_f, the propellant fraction, and the propellant mass, so you can see how much of the vehicle must be fuel.
The wet and dry masses can be in any consistent unit (kilograms, tonnes, pounds) because only their ratio enters the logarithm. As a worked example, an engine with Isp = 300 s and a mass ratio of 3 delivers ve = 2942 m/s and Δv ≈ 3,232 m/s. The exponential nature of the equation is why high delta-v missions demand either very high exhaust velocity or a punishingly large propellant fraction.