Airsoft FPS Limits: FPS, Joules and Field Rules
Every field checks how fast your gun shoots before you play. Here is what the numbers mean and how to stay within them.
What FPS means
FPS (feet per second) is the speed of the BB as it leaves the barrel. Fields measure it with a chronograph at check-in, called chrono. Most use 0.20 g BBs for the test unless they say otherwise.
Many fields also use joules, a measure of energy. Joules account for BB weight, so a heavier BB at a lower speed can carry the same energy as a lighter BB at a higher speed.
FPS to joules
Energy for a 0.20 g BB at common limits. Joules = 0.5 x mass (kg) x velocity (m/s) squared.
| FPS with 0.20 g | Energy | Same energy with 0.25 g |
|---|---|---|
| 350 FPS | 1.14 J | 313 FPS |
| 400 FPS | 1.49 J | 358 FPS |
| 450 FPS | 1.88 J | 402 FPS |
| 500 FPS | 2.32 J | 447 FPS |
Typical limits by game type
These are common ranges, not rules. Your field decides.
| Setting | Common range | Notes |
|---|---|---|
| Indoor CQB | Around 350 FPS | Close distances. Some fields go lower |
| Outdoor rifles | Higher than CQB, often around 400 FPS | Set by each field |
| DMR and bolt-action | Higher allowances where permitted | Usually paired with a minimum engagement distance and semi-auto or bolt-only rules |
How to stay legal at every field
- Read your field's rules before game day and arrive early for chrono.
- Ask which BB weight they test with.
- Use an adjustable-FPS gun. KWA AEG Variable lets you change FPS at the gearbox, so one rifle can meet indoor and outdoor limits.
- Respect minimum engagement distances for higher-powered guns.
New player? Start with the Beginner's Guide to Airsoft.
Frequently Asked Questions
What is a good FPS for airsoft?
One that meets your field's limit. Indoor CQB fields are commonly around 350 FPS and outdoor fields allow more.
What BB weight is used to measure FPS?
Most fields chrono with 0.20 g BBs. Some use heavier BBs or measure joules, so ask your field.
How many joules is 350 FPS?
About 1.14 joules with a 0.20 g BB.
Can I lower the FPS on my airsoft gun?
On KWA AEG Variable models, yes. FPS adjusts at the gearbox with no spring swap.