This Airsoft FPS Calculator helps you quickly work out the velocity (FPS), Joules, or power levels of your airsoft replica based on your chosen BB weight. It’s designed to help players stay within the UK’s legal limits and site-safe rules, and is suitable for all common setups, including AEGs, HPA systems, DMR builds and bolt-action rifles.
Use the calculator below to check your rifle before game day and make sure your setup is compliant.
How the FPS & Joule Calculator Works
This tool lets you calculate either:
- FPS based on Joules and BB weight, or
- Joules based on BB weight and velocity
Just enter your values and the calculator will show the exact power level of your airsoft gun.
Important UK Legal Limits
In the UK, airsoft guns must stay within strict energy limits depending on their firing mode:
- Full Auto / Burst Guns: 1.3 Joules
- DMR (Semi-Only): 2.5 Joules
- Bolt-Action Sniper Rifles: 2.5 Joules
These values are based on accepted UK airsoft guidance and site laws. Breaching these limits can make a replica unsafe or legally non-compliant.
Airsoft BB Calculator
Results:
Joules:
Velocity: fps
Find out if your gun is UK legal or not:
Is Your Airsoft Gun UK Legal?
After entering your values, the calculator will show instantly whether your setup is safe and within UK limits. This helps you avoid issues at chrono and ensures fair and safe gameplay for everyone.
If you regularly tweak your setup, hop-up or BB weight, you can bookmark this page for future reference.
🛡️ Airsoft Safety Rules (On-Site Guidance)
Safety is extremely important to us. All airsoft players must follow the site rules below — these keep everyone safe and ensure smooth, fair gameplay throughout the day.
Legal Compliance
- Always check your replica using the FPS/Joule calculator before arrival.
- All guns must chrono within the UK-accepted limits above.
Safe Zone Rules
- A barrel sock must be fitted at all times in the safe area.
- Attach the barrel sock before connecting your battery.
- Only remove the battery after the barrel sock has been refitted.
- Keep your gun completely safe and unloaded while in the safe zone.
- Outside the safe zone, you may remove the barrel sock when instructed by marshals.
Personal Protective Equipment (PPE)
- Eye protection must be fully sealed to the face.
- Regular glasses are not acceptable unless they include full seal and a rear retention strap.
Pyrotechnics & Smoke
- Only CE-approved pyrotechnics are permitted.
- Smoke grenades must also be CE-approved.
- Smoke cannot be used in very dry conditions due to fire risk.
Play Safe, Be Honest, Have Fun
- Take your hits cleanly
- Follow marshal instructions
- Help maintain a safe, enjoyable environment
Airsoft is at its best when everyone plays fair and looks after one another.
🔗 Want to join a game?
You can find full details about timetables, game formats, equipment, and how a typical day runs on our Airsoft Skirmish Days page.