Rocket Stage Mass Ratio Calculator
Mass ratio is the backbone of rocket performance calculations. Enter the propellant mass, structural dry mass, and any payload riding on the stage. The calculator reports the wet-to-dry mass ratio along with total wet mass, burnout mass, and propellant fraction so you can compare stage designs before running full delta-v math.
This calculator ignores gravity losses, engine Isp, and staging dynamics. Use it as a quick pre-check before performing full mission analysis.
Examples
- 180,000 kg propellant, 22,000 kg dry, 5,000 kg payload ⇒ Stage mass ratio (wet/dry): 5.76 • Wet mass: 207,000.00 kg • Burnout mass: 27,000.00 kg • Propellant fraction: 86.96%
- 90,000 kg propellant, 12,000 kg dry, no payload ⇒ Stage mass ratio (wet/dry): 8.50 • Wet mass: 102,000.00 kg • Burnout mass: 12,000.00 kg • Propellant fraction: 88.24%
FAQ
Does this assume a specific propellant?
No. Enter total propellant mass regardless of the propellant chemistry. The ratio only cares about mass, not energy content.
How do I use this for multi-stage stacks?
Run each stage separately, treating upper stages plus payload as the payload mass of the lower stage. Then feed the resulting ratios into your delta-v calculations.
Can I back into required propellant?
Yes. Rearranging the mass-ratio equation lets you solve for propellant mass if you know the target ratio and dry plus payload mass. Use algebra outside the tool, then verify by plugging the numbers back in.
Additional Information
- Mass ratio equals wet mass (propellant + dry + payload) divided by burnout mass (dry + payload).
- Propellant fraction is simply the share of wet mass made up by fuel and oxidizer, helpful for benchmarking tanks versus structure.
- If you change payload mass, both the mass ratio and burnout mass adjust, illustrating how rideshare payloads eat into performance.