This page shows the rocket fin design formula to know the fin area on rocket. The rocket fin size should compensate for the distinct center of pressure and center of mass of the vehicle. By rocket fin area formula, calculating fin size depends upon the body tube diameter, body tube length. The fin of a rocket helps the rocket to maintain stability, orientation and helps in weather cocking, which is turning into the wind to navigate to its intended flight path.
In this rocket fin area formula, substitute your values for body tube diameter in inches, body tube length in inches to calculate the fin size of your model rocket. You can navigate to the "Rocket Fin Size Calculator" by clicking on the link under the related calculators section and cross check your results.