Enter your Rocket Recovery Mass, Desired Descent Velocity, Parachute Shape, Spill Hole Size, and Air Density to calculate the Required Parachute Diameter that'll bring your rocket down safely — plus the Drag Coefficient (Cd), Reference Area, and Actual Descent Rate so you know exactly what to expect on the way down.
Required Parachute Diameter
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Drag Coefficient (Cd)
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Reference Area
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Actual Descent Rate
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For model rockets, the ideal descent rate is between 3-6 m/s (10-20 ft/s). This provides safe recovery while preventing damage to the rocket or surroundings.
Flat circular parachutes have Cd ≈ 1.3-1.5, hexagonal (parasheet) Cd ≈ 1.2-1.4, hemispherical Cd ≈ 1.2-1.3, and conical parachutes Cd ≈ 0.7-0.9. The calculator automatically applies appropriate coefficients.
A spill hole of 10-20% of the parachute diameter improves stability and reduces oscillation during descent. It slightly increases descent rate but provides more controlled landing.
Higher altitudes have lower air density, requiring larger parachutes for the same descent rate. At 3000m altitude, air density is about 0.9 kg/m³ compared to 1.225 kg/m³ at sea level.
Reference area is the projected area of the parachute perpendicular to the direction of descent. It's used in drag calculations and differs from the actual fabric area of the parachute.
Yes, this calculator works for any model rocket weight from small rockets (10g) to large high-power rockets (5kg). Adjust the recovery mass to include the parachute and recovery system weight.