Joules / FPS Converter
Instantly estimate your replica's power. Slide the BB weight, enter a value in Joules or FPS: the conversion happens automatically, both ways.
Power calculator
Instant conversion · both waysAn estimate, not an exact measurement
Our Joules-to-FPS converter is a valuable tool to give airsoft players a general idea of their replica's power. It's essential to understand, however, that these conversions don't always reflect real-world results, because of a phenomenon known as Joule Creep and various other factors.
Joule Creep occurs when the energy produced (measured in Joules) increases with a heavier BB, even though the velocity (measured in FPS) drops. A heavier BB spends more time in the barrel, letting it build up more energy from the expanding gas.
Other factors also come into play and can make real performance differ from the tool's estimate:
Measure with a chronograph
Our tool is a great starting point, but the most accurate way to determine your replica's power is to test it directly with a chronograph, using the exact BB weight you intend to use in play. That gives you the most reliable information on your gear's performance.