Parachute Descent Rate Calculator

A touchdown under about 4 to 5 m/s is usually gentle enough to protect fins, tubes and electronics. The tool colours the result green below 5 m/s and amber at or above it, and heavier or fragile rockets should aim for the slower end.

At steady descent, drag balances weight, which rearranges to v = sqrt((2 times mass times g) / (air density times drag coefficient times canopy area)). Gravity g is fixed at 9.80665 m/s^2 and the canopy area is pi times the radius squared.

The diameter you enter is treated as the flat distance across the canopy, so area is pi times (diameter over 2) squared. A 0.45 m chute gives about 0.159 m^2. This flat-circle basis is standard for hobby recovery math and lines up with how chute makers state size.

The 0.75 default suits a typical hemispherical or dome canopy. Flat parachutes made from a single sheet often run higher, around 1.5, while spill-hole and shaped canopies vary, so use the figure from your kit or supplier when you have it.

Only for accuracy at altitude or in heat. The 1.225 kg/m^3 default is sea level at 15 C; thinner air at a mountain field or on a hot day lowers density, which raises the descent rate a little because there are fewer air molecules to push against.

Fit a larger canopy or one with a higher drag coefficient. Because area grows with the square of diameter, roughly doubling the chute diameter roughly halves the landing speed, so a small size increase can move an amber result into the green.

No. It reports the steady terminal speed once the canopy is open and inflated. The brief faster fall right after ejection, and any tumbling before deployment, are not part of this model.

Yes. Mass and diameter each have their own unit selector, so you can enter mass in grams and diameter in inches at the same time. The tool converts internally to kilograms and metres before computing.

No. Every figure is computed locally in your browser, so your rocket mass, chute size and other inputs stay on your own device.