Parachute Descent Rate Calculator
Enter your rocket's mass and parachute diameter to find the steady descent rate where drag balances weight. Aim for a soft landing, typically under about 4 to 5 m/s, by sizing the canopy to the rocket.
How to find your parachute descent rate
- Enter the rocket mass in kilograms or grams.
- Enter the parachute (canopy) diameter in metres or inches.
- Adjust the drag coefficient or air density if needed, then read the descent rate.
Examples
Standard hemispherical chute
mass = 0.1 kg, diameter = 0.45 m, Cd = 0.75
area = 0.159 m^2, descent = 3.66 m/s (12.0 ft/s)
Light rocket on a 12 inch chute
mass = 50 g, diameter = 12 in, Cd = 1.5
descent = 2.70 m/s (8.87 ft/s)
Frequently asked questions
What is a safe descent rate for a model rocket?
A landing speed under about 4 to 5 m/s is usually gentle enough to avoid damage. Heavier or fragile rockets call for the lower end of that range.
How is the descent rate calculated?
At a steady descent, drag equals weight. Solving gives v = sqrt((2 x mass x g) / (air density x drag coefficient x canopy area)), where area is PI times radius squared.
What drag coefficient should I use?
The default 0.75 suits a typical hemispherical or dome parachute. Flat sheet chutes are often around 0.8, while shaped or spill hole chutes can differ, so check your maker's figure.
Does air density matter?
Yes. The default 1.225 kg/m^3 is sea level at 15 C. Thinner air at altitude or in heat lowers density, which slightly increases the descent rate.
How do I slow the rocket down?
Use a larger canopy or a chute with a higher drag coefficient. Doubling the canopy diameter roughly halves the descent rate, since area grows with diameter squared.
Related tools
Rocket Altitude Calculator
Estimate the peak altitude of a model rocket from motor thrust, burn time and mass. A no drag kinematic model giving an optimistic upper bound.
Rocket Ejection Delay Calculator
Find the ideal motor ejection delay for a model rocket so the parachute deploys at apogee. Uses burnout velocity or thrust, burn time and mass.
Rocket Stability Calculator
Check model rocket stability from the center of gravity, center of pressure and body diameter. Finds the static margin in calibers and the 1 to 2 rule.
Thrust to Weight Calculator
Calculate the launch thrust to weight ratio of a model rocket from motor thrust and mass. Checks the 5 to 1 safe launch rule. Free and instant.