If you want to konw how to calculate it.. You simply use the drag equation where D = 1/2 rho v^2 S Cd
D= Drag force, in case of parachute this will be the same as the of aircraft weight
rho= air density which you can assume is 1.225 at sea level
v^2= desired decent velocity
S= parachute surface area
Cd= drag coefficient of the parachute (this you cant realy find unless you have a wind tunnel or peform drop tests, however you can assume 0.75 for Cd
Just solve the equation to find S
Just make sure you test parachute with a similar weight before u test it on the aircraft cuz you are guessing the Cd so you will not destroy an aircraft cuz of a guessed value.
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D= Drag force, in case of parachute this will be the same as the of aircraft weight
rho= air density which you can assume is 1.225 at sea level
v^2= desired decent velocity
S= parachute surface area
Cd= drag coefficient of the parachute (this you cant realy find unless you have a wind tunnel or peform drop tests, however you can assume 0.75 for Cd
Just solve the equation to find S
Just make sure you test parachute with a similar weight before u test it on the aircraft cuz you are guessing the Cd so you will not destroy an aircraft cuz of a guessed value.