FPS or “Feet Per Second” is a pretty important term if you’re an airsoft player.. FPS measures the muzzle velocity of your BB as it leaves your airsoft gun when it’s fired. Other countries use (and it should be no surprise here), the Metric System to measure the speed of a BB. They use MPS or Meters Per Second, however, it’s the same basic principle.
Some airsoft players are obsessed with FPS and are doing everything they can to achieve the top position on the airsoft FPS chart. Some players try to stay away from BBS such as the .25 .28 and heavier, because their FPS will be lower with heavier BB types.
What Is Joules?
By definition, Joules is the derived International System unit of kinetic energy. As an example, if your airsoft gun is shooting at 380 FPS with a .20g BB and you switch to a .25g BB, your gun will be shooting a lower 340 FPS. There’s a big difference in FPS but guess what…..you joules will remain the same at 1.34…..SCIENCE!
How Do You Measure Joules?
If you want to figure out the amount of impact your airsoft gun will produce you can use this simple math equation:
J = 0.5 x m x v2
Joules (J) = 0.5 x the mass (m) of the bb (kg) x the speed squared (v2)
Or for those who hate math, like myself, you can use the FPS/Energy Calculator below
Measuring joules can be difficult even with the formula staring you in the face. I’ve always been very bad at math so luckily there are a few joule calculators that you can try out.
Below are the two joule calculators that I prefer to use
These joule calculators are a quick and easy way of figuring out hard your airsoft hits.