# Reference area of a parachute

I am trying to do an aerodynamic drag equation on a descending parachute (the round variety) and have no idea what the reference area on one would be. I know for a sphere, you can use radius*radius*PI to get the reference area. Is that the same for a parachute?

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Using this correction, the table reveals that the ratio between projected diameter and nominal diameter for round parachutes varies between 0.6 and 0.7 This means that given the projected radius, the area is, roughly speaking, somewhere between $2\pi r^2$ and $3\pi r^2$.