This page allows you to predict the speed at which your rockets will descend. Note that it is only an estimate, and values will vary with wind, different air pressures, etc.
Choose the shape of your parachute: Round Hexagonal Square SkyAngle
How did you measure the size of your chute? (For hex and square chutes) Diameter (circular chutes) From one corner to another From one side to another
(Optional) Estimate the descent time by entering the expected altitude when the parachute will open: feet metres
Parachute descent rate calculator version 3.3 by Jordan Hiller.