Rocket Delta-v Calculator (Tsiolkovsky Equation)
Fill in the values and the answer updates as you type.
How the Rocket Delta-v Calculator (Tsiolkovsky Equation) works
The Tsiolkovsky rocket equation says delta-v = Isp × g0 × ln(wet mass ÷ dry mass), where g0 is 9.80665 m/s². Specific impulse measures engine efficiency: about 300 to 460 seconds for chemical rockets. Reaching low Earth orbit needs roughly 9.4 km/s once gravity and drag losses are included. Because of the logarithm, doubling the fuel does not double the delta-v. Example: with Engine specific impulse 350 s, Wet mass (with propellant) 100000 kg, and Dry mass (empty) 20000 kg, the result is Delta-v (m/s) = 5,524; Delta-v (km/s) = 5.52; Mass ratio (wet ÷ dry) = 5.
Inputs and results
The Rocket Delta-v Calculator (Tsiolkovsky Equation) takes 3 inputs and gives 4 results.
What you enter
- Engine specific impulse (s) — starts at 350.
- Wet mass (with propellant) (kg) — starts at 100000.
- Dry mass (empty) (kg) — starts at 20000.
What you get
- Delta-v (m/s)
- Delta-v (km/s)
- Mass ratio (wet ÷ dry)
- Propellant share of launch mass (%)
Example: Rocket Delta-v Calculator (Tsiolkovsky Equation) with the starting values
With engine specific impulse 350 s, wet mass (with propellant) 100000 kg and dry mass (empty) 20000 kg, the calculator returns:
| Delta-v (m/s) | 5,524 |
|---|---|
| Delta-v (km/s) | 5.52 |
| Mass ratio (wet ÷ dry) | 5 |
| Propellant share of launch mass (%) | 80 |
Change any value above and the results update straight away.
Rocket Delta-v Calculator (Tsiolkovsky Equation) FAQ
How do I use the Rocket Delta-v Calculator (Tsiolkovsky Equation)?
Enter engine specific impulse, wet mass (with propellant) and dry mass (empty) in the fields, then read delta-v (m/s), delta-v (km/s), mass ratio (wet ÷ dry) and propellant share of launch mass (%) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Rocket Delta-v Calculator (Tsiolkovsky Equation) calculate?
Velocity change a rocket can produce from its mass and engine efficiency. It returns delta-v (m/s), delta-v (km/s), mass ratio (wet ÷ dry) and propellant share of launch mass (%) from the 3 values you provide.
What values does the Rocket Delta-v Calculator (Tsiolkovsky Equation) start with?
It opens with engine specific impulse 350 s, wet mass (with propellant) 100000 kg and dry mass (empty) 20000 kg so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Rocket Delta-v Calculator (Tsiolkovsky Equation) free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Rocket Delta-v Calculator (Tsiolkovsky Equation) for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.