There are times when you need to find out what the scale of your model is. For myself, often times I am wanting to replace the stock pilot but it doesn't do me much good if I don't know the scale of my model. Below you will find a simple three step method that will supply you with your answer so you can make the right choice for your model.
Let's say I want to find out the scale of my Freewing P-38 Lightning. Let's use millimeters since that is the most common wing measurement for RC electric airplanes.
Take the wingspan of the full scale plane and convert it into millimeters. A quick search online shows that the P-38 Lightning had a 52 feet wingspan. Convert 52 feet to millimeters using a calculator and you will see it is 15,849 millimeters.
Next we divide the full scale wingspan by the model's wingspan. Since the Freewing P-38 Lightning has a 1600mm wingspan simply divide 15,849 by 1,600 which will give you 9.90. (15849 / 1600 = 9.90).
This gives you a ratio of the model to the full scale in millimeters which in this case is 9.90 or in other words approximately 1/10 scale. You round up or down based on the number after the decimal. So 9.4 would be 1/9 scale and so on.
I hope you find this formula easy to use to help you determine your RC model's proper scale.