Free tool · HPA airsoft
HPA calculator
See roughly how many shots you get per fill of your HPA tank – based on tank size, fill pressure, your operating pressure and your dwell. What do the terms mean?
Your tank
Is your tank size given in litres? 1 litre = 61 ci. And 1 bar = 14.5 psi.
Your gun
Filling from your own scuba tank?
Shots per fill
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- Mid-cap magazines of 120 rounds
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- Air per shot
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- Fills from the scuba tank
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An indicative estimate, calibrated against figures reported by players. Full-auto play, leaks, cold and long barrels (higher dwell) mean fewer shots. We assume the tank regulator holds pressure until about 800 psi is left.
How to use the calculator
HPA (high pressure air) powers your gun with compressed air from a tank instead of a battery and a gearbox. The number of shots depends on how much air is in the tank and how much each shot uses. Here are the four numbers you need – and where to find them.
Tank size (ci)
How much air the tank holds, measured in cubic inches (ci). It is printed on the tank label – e.g. “48/3000”, where 48 is the size. If it is given in litres, multiply by 61.
Bigger tank = more shots, but more to carry.
Fill pressure (psi)
How hard the tank is filled. Also on the label – in “48/3000”, 3000 is the pressure. Aluminium tanks are typically 3000 psi, carbon fibre tanks 4500 psi.
4500 psi gives roughly 50 % more air than 3000 psi in the same tank.
Operating pressure (psi)
The pressure your regulator feeds into the gun on every shot. You read it on the regulator pressure gauge. Most HPA guns run at roughly 70–120 psi.
Lower operating pressure = more shots and lower velocity.
Dwell (ms)
How long the valve stays open and releases air behind the BB on each shot, measured in milliseconds. It is set in your engine app, FCU or with DIP switches. If you do not know it, start with 30 ms.
Longer barrels usually need a longer dwell – and use more air.
How do I get more shots out of my tank?
Lower the operating pressure and dwell as far as you can while the gun still shoots consistently and reaches far enough. That is often a better route than a bigger tank. Always check velocity with a chronograph afterwards so you stay within the field limit in m/s – and feel free to let our workshop help with the set-up.
Why does the number not match my gun exactly?
The calculator gives an estimate. Engine type, nozzle, barrel length, leaks, temperature and how much you fire on full auto all affect air consumption. Use the number as a guide when choosing tank size – not as a guarantee.
What does “800 psi left” mean?
The tank regulator can only deliver a stable pressure as long as there is enough pressure in the tank. As it approaches about 800 psi, performance drops and you should refill. That is why we only count the air above 800 psi.
How do I fill my HPA tank?
At the airsoft site, at a dive shop, from your own scuba tank or with a high-pressure compressor. An ordinary bicycle pump or workshop compressor cannot fill an HPA tank. If you fill from a scuba tank, you can select it in the calculator and see how many fills it gives.
I am new to HPA – what do I need?
An HPA gun or an engine for your existing gun, a tank with regulator, a line and possibly a quick-disconnect coupling. See HPA gear, or contact us – our shop in Aulum, Denmark will help you put the right set-up together.
