Airsoft FPS and joules calculator
Enter a chrono reading to get joules and the equivalent FPS on another BB weight.
Energy–
FPS on 0.28g–
m/s on 0.28g–
Estimates assume the same energy on every BB weight. Real guns vary (joule creep), so chrono at your site.
FPS to joules chart
FPS for each energy level and BB weight.
| Joules | 0.20g | 0.25g | 0.28g | 0.32g | 0.40g |
|---|---|---|---|---|---|
| 1.00 J | 328 | 293 | 277 | 259 | 232 |
| 1.14 J | 350 | 313 | 296 | 277 | 248 |
| 1.20 J | 359 | 321 | 304 | 284 | 254 |
| 1.30 J | 374 | 335 | 316 | 296 | 265 |
| 1.50 J | 402 | 359 | 340 | 318 | 284 |
| 1.88 J | 450 | 402 | 380 | 356 | 318 |
| 2.00 J | 464 | 415 | 392 | 367 | 328 |
| 2.32 J | 500 | 447 | 422 | 395 | 353 |
| 2.50 J | 519 | 464 | 438 | 410 | 367 |
| 3.00 J | 568 | 508 | 480 | 449 | 402 |
Common UK site limits
| Type | FPS on 0.20g | FPS on 0.25g | Joules | Minimum engagement distance |
|---|---|---|---|---|
| AEG / GBB (full auto) | 350 | 313 | 1.14 J | None |
| DMR (semi-auto only) | 450 | 402 | 1.88 J | 20–30m |
| Bolt-action sniper | 500 | 447 | 2.32 J | 30–40m |
Limits vary between sites. Check your site's rules.
How it works
Energy is E = ½mv², with m in kilograms and v in metres per second. A gun gives roughly the same energy to any BB, so a heavier BB leaves the barrel slower. The calculator works out the energy from your reading, then the speed that energy gives the new BB.
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