Airsoft Joules FPS Conversion

FPS Chart for Airsoft Guns

FPS is the abbreviation for Feet Per Second, it is a measure of velocity to gauge the speed of BBs as it leaves the barrel of your airsoft gun or in real steel lingo "muzzle velocity". Some countries using Metric System uses MPS which stands for Meters Per Second while other countries like here in the United States we use FPS which stands for Feet Per Second (English System); and as a rule of thumb 1 FPS = .3048 MPS.

A lot of airsoft players are very particular about the FPS of their BBs. Some players try to stay away from heavier BBs like .25, .28, and so on, because their FPS is lower with those types of BB weight. While it is true, the more important measure to look at is how much kinetic energy the BB has while it was leaving the airsoft gun's barrel.

Joules is the derived International System unit of kinetic energy. Given everything the same in your airsoft gun (compression, spring, barrel length, etc), FPS is relative to the BB weight you are using but the kinetic energy it produces is always the same.

This means that if your airsoft gun is shooting 380 FPS with a .20g BB and you switch to a .25g BB your gun will be shooting 340 FPS. There's a big difference in FPS but the kinetic energy it carries on flight will be the same, 1.34 Joules, regardless of what BB weight you use. Hence once the BB hit your target, 1.34 Joules will be transfered to the target.

To calculate kinetic energy (in Joules) we used this formula:

KE ( in Joules) = 0.5 ( a half) x the mass of the something (in kg) x the speed squared (in Meters/Second)

KE = 0.5 . m . v^2

As an example for the above formula; a .20 gram bb is moving at 328 feet per second [.5 * (.20 grams / 1000 kilograms) x (328 feet per second x .3048 meters per second) ^2 is equal to 0.999488 or 1 Joule.

Now enough of this boring geeky stuff. We have formulated a table that shows you the kinetic energy (Joules) in relation to your airsoft gun's velocity (FPS/MPS). These numbers were derived from using the above formula. Now I am not a physics or mathematics expert and these are just theoretical numbers. Use this as a theoretical guideline and not as an exact science nor the standard for all airsoft games. Contact your game organizers for FPS limit, rules and regulations.