Parachute Descent Rate Calculator
This tool will plot the descent rate of two parachutes around the weight you specify. To use the tool:
1) Enter the parachute model you want to plot. The primary parachute goes on the left side. The optional parachute to compare with goes on the right. Leave this blank if you do not want a second parachute plotted. The form fields will auto-populate with the parachute's diameter and Cd (coefficent of drag).
2) You can override the diameter or the Cd to test how a different parachute would perform or how Cd affects performance.
3) Enter the target weight. The default is 11 lbs (5Kg). The plot will then graph the parachute performance based on weight.
4) Hit return to update the plot after you override values, or press "Update" after changing any values.
5) Compare our parachutes alongside the products of other manufacturers.
* IMPORTANT NOTE ABOUT REFERENCE DIAMETER: Reference Diameter is used to calculate the descent velocity drag area. For Fruity Chutes parachutes, this diameter is the same as the opening diameter of the parachute. The drag area of the parachute is calculated as Pi * D / 4, where D is the reference diameter.
For flat sheet parachutes such as Top Flight, the reference diameter is the flattened diameter of the parachute - again, the diameter quoted by the manufacturer. For some manufacturers, the parachute's size is measured by the distance (circumference) across the canopy. Alternatively, in some cases, it's just a model number and we are not sure of the exact size. This includes Rocket Man, Spherachute, Sky Angle and Giant Leap TAC chutes. For these, the equivalent reference diameter is calculated based on the geometry of the canopy while in flight. This then becomes the reference diameter used to calculate the descent velocity.
For these parachutes, you will notice that the diameter is different from the size of the manufacturer. For example, a Spherachute 120" parachute has an equivalent diameter of 76.4 inches. However, the Cd of the Spherachute parachute is set to 1.5 so the resulting descent rate matches the manufacturer's data. For these parachutes, the Cd is adjusted so the resulting descent rate matches the manufacturers' published rates for that model. This has occasionally caused some confusion for people using the calculator on other manufacturers' parachutes.