FPS ↔ joules calculator
Energy (joules) is what a field chronograph really measures. Enter your reading and see what it means for each BB weight.
Your reading
Result
- Energy
- 1.14 J
- Speed
- 106.7 m/s
- FPS
- 350 FPS
Within the limit · Margin: 0.00 J
With other BB weights (same energy)
| BB | Energy | m/s | FPS |
|---|---|---|---|
| 0.20 g | 1.14 J | 106.7 | 350 |
| 0.23 g | 1.14 J | 99.5 | 326 |
| 0.25 g | 1.14 J | 95.4 | 313 |
| 0.28 g | 1.14 J | 90.2 | 296 |
| 0.30 g | 1.14 J | 87.1 | 286 |
| 0.32 g | 1.14 J | 84.3 | 277 |
| 0.36 g | 1.14 J | 79.5 | 261 |
| 0.40 g | 1.14 J | 75.4 | 247 |
| 0.43 g | 1.14 J | 72.8 | 239 |
| 0.45 g | 1.14 J | 71.1 | 233 |
On a real replica, heavier BBs keep roughly the same energy and fly slower: that is why fields limit in joules. It is an approximation; the field chronograph is what counts.
How it works
BB energy is E = ½ · m · v², with mass in kilograms and speed in metres per second. 1 m/s is 3.28 FPS.
So 350 FPS with 0.20 g (≈ 1.14 J) is not 350 FPS with 0.30 g: at the same energy, a 0.30 g BB leaves at about 286 FPS.
The limits shown are common references; every field, association or event sets its own, along with minimum engagement distances. Always check their rules.
Frequently asked questions
How many joules is 350 FPS?
With a 0.20 g BB, 350 FPS is about 1.14 J. With a 0.25 g BB the same 350 FPS would be 1.42 J, which is why it is best to talk in joules or always state the BB weight.
Why do fields chrono with 0.20 g?
Because it is the most common reference weight. If your replica gives 1.14 J with 0.20 g, heavier BBs will give similar or slightly higher energy, especially on HPA or with a well-matched cylinder.
Which limits are common?
As a reference: CQB around 1 J, assault 1.14 J (350 FPS with 0.20 g), DMR around 1.88 J and sniper around 2.32 J, with minimum engagement distances. Each field may use different values.
Does it work for HPA and springs?
Yes, the conversion is pure physics and applies to any system. The weight table assumes constant energy, which roughly holds; for the exact value with your BB, chrono it.