Airsoft FPS to Joules Calculator
Understanding Airsoft FPS and Joules
In airsoft, muzzle velocity is traditionally measured in FPS (Feet Per Second). However, FPS alone doesn't tell the whole story of how much "punch" a BB carries. To measure the actual impact force, we use Joules, which represents the kinetic energy of the projectile.
The Physics of the Calculation
The energy is calculated using the standard kinetic energy formula: E = ½mv²
- m is the mass of the BB in kilograms.
- v is the velocity in meters per second (m/s).
Because most airsoft chronographs measure in FPS and grams, this calculator automatically converts those units to metric before applying the physics formula. This is crucial for understanding "Joule Creep," where heavier BBs may carry more energy than lighter ones even if the FPS appears lower.
Common BB Weight Energy Reference
| FPS (w/ 0.20g) | Joules | FPS (w/ 0.25g) | FPS (w/ 0.30g) |
|---|---|---|---|
| 300 | 0.84 J | 268 | 245 |
| 350 | 1.14 J | 313 | 286 |
| 400 | 1.49 J | 358 | 327 |
| 450 | 1.88 J | 402 | 367 |
| 500 | 2.32 J | 447 | 408 |
Why Joule Limits Matter
Most airsoft fields have strict safety limits. A common "CQB" (Close Quarters Battle) limit is 1.14 Joules (equivalent to 350 FPS with a 0.20g BB). Outdoor fields often allow up to 1.49 Joules (400 FPS with 0.20g) for rifles, and higher limits for bolt-action sniper rifles. Always measure your rifle with the actual BB weight you intend to use to ensure you aren't "hot" and violating field safety rules.