Shopping Cart
- L'équipe Powair6
- Outils
- 7 likes
- 1818 views
- 2 comments
Kinetic energy
1.14
J
0.20 g BB · 106.7 m/s
Measure velocity using the same BB weight you actually use on the field.
What is the FPS / joules conversion for?
In airsoft, two units come up all the time. FPS (feet per second) measures the velocity of the BB as it leaves the barrel, while joules (J) measure the kinetic energy carried by the BB.
FPS alone do not tell the whole story. The same airsoft replica can produce very different FPS readings depending on the BB weight being used. A heavier BB will generally travel more slowly than a lighter BB, even though the energy produced by the replica may be similar.
Joules are therefore the better measurement for comparing actual muzzle energy. This is why many airsoft fields and national regulations use joules when defining power thresholds.
The converter above works in both directions. Enter the FPS and BB weight to calculate energy in joules, or enter the energy in joules to calculate the corresponding FPS for a given BB weight.
The FPS to joules formula
The converter uses the standard kinetic energy formula:
E = ½ × m × v²
E = kinetic energy in joules
m = BB mass in kilograms
v = velocity in metres per second
m = BB mass in kilograms
v = velocity in metres per second
Since FPS are expressed in feet per second, the velocity first needs to be converted to metres per second: 1 foot = 0.3048 metre.
For example, a 0.20 g BB travelling at 350 FPS is moving at approximately 106.7 m/s. Using the kinetic energy formula, this corresponds to roughly 1.14 joules.
For the reverse calculation, velocity is isolated using v = √(2E / m), then converted from metres per second back to FPS.
FPS to joules conversion table
Here are some common FPS values calculated for 0.20 g and 0.25 g BBs.
| FPS | Joules — 0.20 g | Joules — 0.25 g |
|---|---|---|
| 180 FPS | 0.30 J | 0.38 J |
| 200 FPS | 0.37 J | 0.46 J |
| 240 FPS | 0.54 J | 0.67 J |
| 280 FPS | 0.73 J | 0.91 J |
| 300 FPS | 0.84 J | 1.05 J |
| 330 FPS | 1.01 J | 1.26 J |
| 350 FPS | 1.14 J | 1.42 J |
| 370 FPS | 1.27 J | 1.59 J |
| 400 FPS | 1.49 J | 1.86 J |
| 430 FPS | 1.72 J | 2.15 J |
| 450 FPS | 1.88 J | 2.35 J |
| 500 FPS | 2.32 J | 2.90 J |
| 550 FPS | 2.81 J | 3.51 J |
Values are rounded. Actual measured energy can vary depending on the replica, BB weight, hop-up setting, gas pressure and other factors.
Airsoft joule limits by country
There is no single European airsoft power limit. The rules vary considerably from country to country, and the figures are not always directly comparable.
In some countries, the figure shown in the law is a legal classification ceiling. It defines whether a device can legally be treated as an airsoft or low-energy replica. It does not necessarily mean that you can use a replica at that power during an airsoft game.
Legal ceiling ≠ field limit
A country may legally classify an airsoft device at a relatively high energy level while airsoft organisations impose much lower limits during play. The Netherlands is a good example: the legal definition reaches 3.5 J, but NABV playing limits are substantially lower.
🇫🇷 France
< 2 J threshold
French law states that devices firing a projectile or projecting gas with a muzzle energy below 2 joules are not considered weapons under the relevant section of the Internal Security Code.
The 2 J figure should therefore be understood as an important legal threshold, rather than a recommended playing power.
On the field:
airsoft organisers commonly impose lower limits depending on replica
type and minimum engagement distance.
🇳🇱 Netherlands
3.5 J legal ceiling
Dutch regulations define an airsoft device as an air-, gas- or spring-powered weapon resembling a firearm with a maximum shooting energy of 3.5 joules.
This 3.5 J figure is a legal classification ceiling. It should not be confused with the maximum energy permitted during normal airsoft games.
NABV playing limits:
Full-auto / standard replicas: 1.20 J
DMR: 1.70 J
Bolt-action sniper: 2.30 J
Additional BB-weight and minimum-distance rules apply.
Full-auto / standard replicas: 1.20 J
DMR: 1.70 J
Bolt-action sniper: 2.30 J
Additional BB-weight and minimum-distance rules apply.
🇩🇪 Germany
0.5 J play exemption
Germany cannot accurately be reduced to one maximum airsoft joule figure.
Devices intended for play that cannot exceed 0.5 J benefit from a broad exemption under the German Weapons Act.
Above 0.5 J, air-, spring- and cold-gas-powered weapons enter a different legal framework. Weapons producing no more than 7.5 J may in certain circumstances be acquired and possessed without a firearms licence when they comply with the required German approval and marking rules.
Important:
7.5 J is not an "airsoft playing limit". Full-auto capability and
other characteristics are subject to additional restrictions under
German weapons law.
🇪🇸 Spain
3.5 J legal ceiling
Spanish national regulations define airsoft sporting weapons as firing polymer-based projectiles weighing no more than 0.45 g, with a maximum diameter of 8 mm and a muzzle energy not exceeding 3.5 J.
Again, the 3.5 J figure is a legal classification ceiling, not a universal airsoft field limit.
On the field:
organisers may impose substantially lower energy limits. Additional
rules concerning Category 4 weapons and local documentation also
apply in Spain.
🇵🇹 Portugal
1.3 J
Portuguese law defines a recreational firearm reproduction as a device capable only of firing non-metallic spherical projectiles with muzzle energy not exceeding 1.3 J for calibres of 6 mm or less using compact ammunition.
Portuguese law also contains specific fluorescent marking requirements intended to distinguish recreational replicas from real firearms.
On the field:
the organiser may set a lower maximum than the national legal
threshold.
🇧🇪 Belgium
No single J ceiling
Belgian federal guidance lists airsoft replicas among freely available non-firearm weapons.
Unlike France, Portugal or Spain, the Belgian federal guidance does not provide one simple airsoft-specific joule figure that can safely be presented as a universal national maximum.
Check locally:
acquisition, carrying, transport and use remain subject to Belgian
weapons rules, while individual airsoft fields set their own playing
limits.
🇨🇭 Switzerland
No simple J threshold
Switzerland does not use a simple low-energy airsoft exemption based solely on joules.
Airsoft replicas that can be mistaken for real firearms are classified as weapons under Swiss law. Fedpol specifically states that even an airsoft replica producing less than 0.5 J can still be legally classified as a weapon in Switzerland.
Important:
the German 0.5 J rule does not apply in Switzerland. Written-contract
and import requirements may also apply.
🇮🇹 Italy
Max. 1 J
Italian law defines "softair" devices as firing brightly coloured plastic BBs using compressed air or gas, provided that the energy of each projectile does not exceed 1 joule.
Unlike most of the figures on this page, the Italian measurement is specifically taken one metre from the muzzle.
Additional rules:
Italian law also includes age and red-muzzle marking requirements.
Important — please verify the rules before playing:
the information above is provided for general guidance only and is not
legal advice.
Airsoft legislation can change, and the legal status of a replica may depend on much more than muzzle energy. Relevant factors can include firing mode, replica appearance, calibre, projectile weight, age restrictions, markings, registration, association membership, transport, import rules and local regulations.
Field rules are also separate from national law and are often much more restrictive. Always check the latest information from the relevant national or local authority and the rules of the specific airsoft field or event before purchasing, importing, modifying, transporting or using an airsoft replica.
Airsoft legislation can change, and the legal status of a replica may depend on much more than muzzle energy. Relevant factors can include firing mode, replica appearance, calibre, projectile weight, age restrictions, markings, registration, association membership, transport, import rules and local regulations.
Field rules are also separate from national law and are often much more restrictive. Always check the latest information from the relevant national or local authority and the rules of the specific airsoft field or event before purchasing, importing, modifying, transporting or using an airsoft replica.
Legal overview reviewed in September 2026.
Why can field limits be much lower than the legal limit?
A legal threshold determines how a replica is classified under national law. An airsoft field has a different objective: keeping games safe at realistic engagement distances.
This explains why a country can theoretically have a legal classification ceiling of 3.5 J while a standard assault replica is only allowed to operate at around 1.2 J during organised play.
Fields may also use different limits depending on the replica category. A bolt-action sniper may be allowed more energy than an assault rifle because the player must observe a longer minimum engagement distance.
Example: the Netherlands
Dutch law uses 3.5 J in the legal definition of an airsoft device, but current NABV safety rules limit devices with full-auto capability to 1.20 J, DMRs to 1.70 J and bolt-action replicas to 2.30 J, together with minimum engagement distances and other conditions.
How to measure your airsoft replica's power correctly
- Use a reliable chronograph and enter the actual BB weight you use.
- Fire several BBs of the same weight and use the average rather than relying on a single shot.
- Re-test the replica after changing the spring, nozzle, barrel, gas pressure, HPA regulator or other components that can affect output.
- Remember that a heavier BB will normally produce a lower FPS reading. This does not automatically mean the replica is producing less energy.
- Measure with the BB weight you actually intend to use in game, particularly with gas and HPA replicas where joule creep may occur.
- Follow the chronograph procedure specified by the field or event organiser, even if it differs from the method you normally use.
FPS and joules FAQ
How do you convert FPS to joules?
Convert the FPS value to metres per second by multiplying it by 0.3048, convert the BB weight from grams to kilograms, then use the kinetic energy formula E = ½ × m × v². The converter at the top of this page does this automatically.
How many joules is 350 FPS?
At 350 FPS, a 0.20 g BB carries approximately 1.14 J. A 0.25 g BB travelling at the same 350 FPS carries approximately 1.42 J.
This is why FPS cannot be accurately converted to joules without knowing the BB weight.
Are FPS and joules the same thing?
No. FPS measures velocity, while joules measure kinetic energy. Two BBs travelling at exactly the same FPS can carry different amounts of energy if their weights are different.
Why does BB weight matter?
Kinetic energy depends on both mass and velocity. A heavier BB normally travels more slowly, but its greater mass means it can still carry a similar amount of energy.
Some replicas, especially certain gas and HPA systems, can also exhibit joule creep, where heavier BBs result in higher measured muzzle energy.
Which BB weight should I use when chronoing?
For understanding the real output of your replica, measure using the BB weight you actually use in game. You must also follow whatever chronograph method and test BB weight the field requires.
Is 3.5 joules legal for airsoft in Europe?
There is no Europe-wide answer. In the Netherlands and Spain, 3.5 J appears as a legal classification ceiling for airsoft devices covered by the relevant national rules.
That does not mean that an ordinary airsoft player can necessarily use a replica at 3.5 J during a game. Field and federation limits can be far lower. For example, Dutch NABV rules limit standard / full-auto-capable replicas to 1.20 J.
What is the legal joule limit for airsoft in France?
Under French law, devices firing projectiles with a muzzle energy below 2 J are excluded from the definition of weapons under the relevant section of the Internal Security Code.
Individual airsoft fields can, and commonly do, impose lower power limits.
What is the airsoft joule limit in Germany?
Germany does not have one simple universal airsoft joule limit. Devices intended for play at no more than 0.5 J benefit from a broad exemption.
Higher-powered air-, spring- and cold-gas weapons are subject to a different legal framework, including approval and marking rules. The often-mentioned 7.5 J figure is therefore not an airsoft field limit.
What is the airsoft joule limit in Portugal?
Portuguese law uses a maximum muzzle energy of 1.3 J for recreational firearm reproductions firing compact non-metallic projectiles in calibres of 6 mm or less. Marking and other legal requirements also apply.
What is the airsoft joule limit in Italy?
Italian rules define softair devices with projectile energy not exceeding 1 J measured one metre from the muzzle. Additional age and marking requirements apply.
Is there an airsoft joule limit in Belgium or Switzerland?
Neither country can accurately be summarised using one simple nationwide airsoft joule figure.
Belgium treats airsoft devices as freely available non-firearm weapons under federal guidance, subject to other weapons rules. Switzerland classifies airsoft replicas that can be mistaken for real firearms as weapons regardless of a simple low-energy threshold.
Comments (2)