🚀 Multi-Stage Rocket Delta-v & Mass Budget Planner
🚀 Multi-Stage Rocket Delta-v & Mass Budget Planner
Stack up to five stages, enter propellant, dry mass and Isp for each, and get stage-by-stage delta-v, liftoff mass, payload fraction and the margin against your mission target.
Delta-v contributed by each stage, against the target. Segments run in firing order from the left.
Stage-by-stage mass budget
| Stage | Propellant | Dry | Wet m₀ | Final m_f | Mass ratio | Δv | Cumulative |
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How the staging arithmetic works, and why the total is not the sum of the stages you first expect
Tsiolkovsky, stage by stage. Each stage's ideal delta-v is Δv = Isp·g₀·ln(m₀/m_f), where m₀ is the mass at that stage's ignition and m_f is what remains after its propellant is burned. For a stacked rocket, stage 1 carries the propellant and dry mass of every later stage plus the payload. After stage 1 separates, stage 2 carries only itself, the stages above it and the payload. That is why the first stage usually contributes the most delta-v even when its Isp is the lowest: it is pushing the whole stack.
What the dry mass must include. The dry mass of a stage is everything that is not its propellant but is still attached at burnout: tankage, engine, thrust structure, avionics, pressurisation, insulation, interstage and any residual propellant. The payload is entered separately and is not part of any stage's dry mass. A stage that does not separate, or a payload adapter that stays attached, must be accounted for where it really is.
Ideal versus delivered. The sum shown here is ideal delta-v. A real Earth launch loses roughly 1.5–2 km/s to gravity and drag before reaching low Earth orbit; steering losses and a finite burn add more. Deep-space manoeuvres have much smaller losses but still need margin for navigation and reserve propellant. A useful rule is to add the losses to the target before comparing, or to treat this as the vacuum budget after the ascent.
Payload fraction and staging. Payload fraction is payload divided by liftoff mass. It improves when dry mass is small relative to propellant, when Isp is high, and when the stage count is matched to the delta-v requirement. More stages usually buy delta-v but add dry mass, separation hardware and failure modes. Optimal staging for a fixed total delta-v spreads the work across stages so that the mass ratio of each is similar; this calculator lets you test that by hand.
Not modelled. Gravity and drag losses, finite burn times, engine throttling, propellant residuals, boil-off, stage separation dynamics, payload fairing jettison, and structural limits. Use a trajectory simulation for ascent and a dedicated mass-budget model for hardware.
Last reviewed: 2026-10-19. A conceptual mass-budget aid, not a flight-qualified performance calculation.