Airsoft joule ↔ FPS converter
Enter the power in FPS, joules or m/s and the BB weight: get the other values instantly, plus the velocity with different BB weights.
Calculate
Same energy with different BB weights
| BB weight | FPS | m/s |
|---|
For information only, based on the energy the manufacturer declares for this version. Not legal advice: always check current local law and the version the shop sells.
FPS equal to 1 joule
The velocity that equals exactly 1 J for each BB weight. Below these values the energy stays under 1 joule.
| BB weight | FPS at 1 J | m/s at 1 J |
|---|---|---|
| 0.12 g | 424 | 129.1 |
| 0.20 g | 328 | 100.0 |
| 0.23 g | 306 | 93.3 |
| 0.25 g | 293 | 89.4 |
| 0.28 g | 277 | 84.5 |
| 0.30 g | 268 | 81.6 |
| 0.32 g | 259 | 79.1 |
| 0.36 g | 245 | 74.5 |
| 0.40 g | 232 | 70.7 |
| 0.43 g | 224 | 68.2 |
| 0.45 g | 219 | 66.7 |
FPS to joules: quick table
| FPS | m/s | Energy (0,20 g) | Energy (0,25 g) |
|---|---|---|---|
| 250 | 76.2 | 0.58 J | 0.73 J |
| 275 | 83.8 | 0.70 J | 0.88 J |
| 300 | 91.4 | 0.84 J | 1.05 J |
| 325 | 99.1 | 0.98 J | 1.23 J |
| 350 | 106.7 | 1.14 J | 1.42 J |
| 375 | 114.3 | 1.31 J | 1.63 J |
| 400 | 121.9 | 1.49 J | 1.86 J |
| 425 | 129.5 | 1.68 J | 2.10 J |
| 450 | 137.2 | 1.88 J | 2.35 J |
| 475 | 144.8 | 2.10 J | 2.62 J |
| 500 | 152.4 | 2.32 J | 2.90 J |
| 525 | 160.0 | 2.56 J | 3.20 J |
| 550 | 167.6 | 2.81 J | 3.51 J |
| 575 | 175.3 | 3.07 J | 3.84 J |
How it is calculated
A BB's energy is E = ½ · m · v², with mass m in kilograms and velocity v in metres per second. A 0.20 g BB weighs 0.0002 kg.
To go from FPS to m/s multiply by 0.3048, since one foot is 0.3048 metres. Example: 350 FPS × 0.3048 = 106.7 m/s; with 0.20 g BBs the energy is ½ × 0.0002 × 106.7² ≈ 1.14 J.
Manufacturers almost always quote FPS with 0.20 g BBs. Heavier BBs leave the barrel slower, but the energy stays about the same: that is why fields and laws use joules.
Values are theoretical: hop-up, air seal and replica type can change the result slightly. For an exact value you need a chronograph.