Free tool
Joule calculator
Convert between joules, m/s and fps in seconds – and check whether your airsoft gun is within your site’s limits. What do the terms mean?
- Velocity
- 100 m/s
- Equivalent with 0.20 g
- 100 m/s
How to use the calculator
Joules are the energy the BB carries as it leaves the barrel. It is the figure airsoft sites use to set how hard you may shoot – because energy is what decides how much a hit hurts and how much harm it can do. Here are the three figures you need to know.
BB weight (g)
How much a single BB weighs. It is printed on the bag – e.g. 0.20 g, 0.25 g or 0.30 g. Sites usually chronograph with 0.20 g BBs, so every gun is measured the same way.
Heavier BB = lower velocity, but almost the same energy.
Velocity (m/s)
How fast the BB leaves the barrel, measured with a chronograph in metres per second. American manufacturers often quote fps (feet per second) – 1 m/s equals 3.28 fps.
Double the velocity gives four times the energy.
Energy (joules)
Calculated as 0.5 × weight (kg) × velocity² (m/s). A 0.20 g BB at 100 m/s gives 0.5 × 0.0002 × 10,000 = 1.0 J. The calculator does it for you – and also shows what your figure equals with 0.20 g BBs.
The site limit applies to the joule figure.
Typical values
| Weight | Velocity | Energy |
|---|---|---|
| 0.20 g | 100 m/s (328 fps) | 1.00 J |
| 0.20 g | 129 m/s (423 fps) | 1.66 J |
| 0.25 g | 90 m/s (295 fps) | 1.01 J |
| 0.28 g | 85 m/s (279 fps) | 1.01 J |
| 0.40 g | 100 m/s (328 fps) | 2.00 J |
How hard am I allowed to shoot at the site?
Every site sets its own limits, and they often differ for rifles, snipers and indoor games. Guns are chronographed at the entrance. Check the rules of your local site before you play.
Why is my gun measured with 0.20 g BBs?
So that every gun is measured the same way. The energy is almost the same with heavier BBs, but velocity is easier to compare when everyone uses the same weight. That is why the calculator also shows what your result equals with 0.20 g.
Does my gun get more powerful with heavier BBs?
No, not noticeably. The energy is almost the same – the BB just flies slower. On the other hand, heavier BBs are less affected by wind and often hold their line better at long range.
How do I lower or raise the energy?
On an AEG you usually change the spring. On HPA you adjust the operating pressure and dwell – see the HPA calculator. On gas guns it depends on the gas and the valves. Always check with a chronograph afterwards, or let our workshop do it for you.
Why should I measure after an upgrade?
A new spring, inner barrel, hop-up bucking or a different gas can change the velocity more than you would expect. Measure your gun before you go to the site so you are not turned away at the entrance.
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