Estimate how many BBs per second your AEG will fire. Enter your gear ratio, your motor’s rated speed and your battery voltage to see the likely rate of fire, plus how long it takes to empty a mid-cap or hi-cap magazine.
How the ROF estimate works
In an AEG, the motor turns the gears and every full turn of the sector gear cocks and releases the piston once, firing one BB. So the rate of fire is the motor’s speed divided by the gear ratio, converted from per minute to per second.
Example: a 30,000 rpm motor (rated at 11.1V) on a 7.4V LiPo with standard 18.72:1 gears. 30,000 × (7.4 ÷ 11.1) = 20,000 rpm at the motor. 20,000 ÷ 18.72 ÷ 60 = 17.8 rps with no load, or about 13 rps in practice.
ROF by gear ratio and battery
Estimated rounds per second for a 30,000 rpm motor (rated at 11.1V) with each gear set and battery.
| Gear ratio | 7.4 V LiPo | 8.4 V NiMH | 9.6 V NiMH | 11.1 V LiPo |
|---|---|---|---|---|
| 13:1 super high speed | 19 rps | 22 rps | 25 rps | 29 rps |
| 16.32:1 high speed | 15 rps | 17 rps | 20 rps | 23 rps |
| 18.72:1 standard | 13 rps | 15 rps | 17 rps | 20 rps |
| 24:1 torque-up | 10 rps | 12 rps | 14 rps | 16 rps |
| 32:1 high torque | 8 rps | 9 rps | 10 rps | 12 rps |
Ways to change your rate of fire
- Battery voltage: the simplest change. 7.4V to 11.1V raises ROF sharply but adds wear.
- Gear ratio: high-speed gears raise ROF; pair them with a strong motor so they still pull your spring.
- Motor: a high-speed motor raises ROF; a high-torque motor improves trigger response with heavier springs.
- Spring: a lighter spring lets the motor spin faster, but lowers your fps.
- Wiring and MOSFET: low-resistance wiring and a MOSFET deliver more of the battery’s power to the motor.
New to the terms? Our airsoft glossary explains them, and the FPS to Joules Calculator shows what a spring change does to your power.
Frequently asked questions
What is a good rate of fire for airsoft?
Most players are happy with 15 to 20 rounds per second. That’s quick enough for short, effective bursts without emptying a mid-cap in seconds. Some players build 25 to 30+ rps guns, but a few sites and games limit full-auto or rate of fire, so check the rules.
How does gear ratio affect ROF?
The gear ratio is how many times the motor turns for one turn of the sector gear, and each sector gear turn fires one BB. A lower ratio such as 13:1 fires faster but needs a stronger motor to pull the spring; a higher ratio such as 32:1 is slower but has lots of torque for heavy springs.
Does an 11.1V battery increase ROF?
Yes. Motor speed rises roughly in line with voltage, so moving from 7.4V to 11.1V can increase your rate of fire by around 50%. It also adds stress to the gearbox and trigger contacts, so it’s best kept for upgraded guns with a MOSFET. Our Airsoft Battery Calculator explains the differences between packs.
Why is my real ROF lower than the calculator?
Motors slow down under load. A stiffer spring, worn or poorly shimmed gears, a weak battery or thin wiring all reduce the real rate of fire. The calculator allows for typical losses and gives a range, but a chrono with a ROF mode is the only way to measure your gun exactly.
What is trigger response, and is it the same as ROF?
No. Trigger response is how quickly the gun fires after you pull the trigger, which matters most for semi-auto shooting. ROF is how many BBs per second it fires on full-auto. High-torque motors, 11.1V LiPos, MOSFETs with active braking and short-stroking all improve trigger response.
Power up your AEG
LiPo and NiMH batteries, smart chargers and LiPo safe bags.
More airsoft tools
Airsoft Battery Calculator
LiPo, LiFePO4 and NiMH voltages, C rating, charge time, storage voltage and a rough shots-per-charge figure.
Open the calculator →FPS to Joules Calculator
Convert airsoft fps to joules (and back) for any BB weight, then check it against typical UK site limits.
Open the calculator →Airsoft BB Calculator
How many BBs are in a bag, how many mags it fills, how many game days it lasts and the cost per shot.
Open the calculator →Results are estimates for guidance. Always follow your site’s chrono and safety rules, and your gun maker’s advice.