Enter a pellet's weight in grains and its velocity in feet per second to get foot-pounds of energy (FPE) and joules, calculated live as you type. This tool converts your chronograph's FPS reading directly into FPE, no manual math required. Switch to Compare to check FPE across a few pellets side by side.
Foot-pounds of energy, often written as ft-lbs or FPE, is the kinetic energy a pellet carries when it leaves the muzzle. It combines weight and velocity into a single number, which matters because velocity alone is misleading, a very light pellet can post an impressive FPS number on the box while carrying less actual energy than a heavier pellet moving slower. FPE is what actually determines how a rifle performs on pest control, hunting, or just punching a can.
The formula is FPE = (grains × fps²) ÷ 450,240. Pellet weight in grains gets multiplied by the square of its velocity in feet per second, then divided by 450,240, a constant that converts the result into foot-pounds. The calculator above does this instantly, but it's the same math you'd use by hand with just a scale and a chronograph reading.
You'll need a chronograph to get a real velocity reading. Most chronographs use two sensors spaced a known distance apart; the device times how long a pellet takes to cross both, then calculates FPS from that. Shooting over a chronograph with your actual hunting or target pellet, not just the lightest alloy pellet that came with the rifle, gives you a realistic number to plug into this calculator.
Switch the calculator above to Compare to check FPE across a few pellet weights at once, useful when you've chronographed a couple of pellet brands through the same rifle and want to see how weight and velocity trade off. Add up to four pellets side by side.
These are general reference points pulled from common airgun hunting guidance, not hard rules. Shot placement and range affect a clean, humane result more than raw power does, and legal power limits vary by country and state, always check current regulations where you live.
| Use | FPE Range |
|---|---|
| Small pests (rats, starlings) | 4–10 FPE |
| Squirrels, rabbits, small game | 10–20 FPE (10 FPE is commonly cited as a practical minimum for an ethical kill) |
| Larger pests (raccoon-sized) | 20–30 FPE |
| Big-bore hunting (hogs, coyotes, larger game) | 40+ FPE |
Some countries regulate airgun power specifically by FPE. The UK, for example, sets 12 FPE as the threshold above which a rifle requires a firearms certificate. Rules like this change over time and vary by jurisdiction, so treat any specific number here as a starting point, not a final answer.
Want the fuller picture, how FPE compares across spring, PCP, and CO2 platforms, and common misconceptions about power? Read our guide to understanding airgun FPE.
This calculator is free to embed anywhere, including WordPress, no plugin required. Paste the code below into a Custom HTML block (or anywhere in your page's HTML):
<iframe src="https://airgunguide.com/embed/airgun-fpe-calculator.html" width="100%" height="590" style="max-width:420px;" title="Airgun FPE Calculator"></iframe>
<script src="https://airgunguide.com/js/embed-listener.js"></script>The script after the iframe lets the calculator resize itself automatically as you switch modes or add pellets, so it never shows an internal scrollbar. If you embed more than one AirgunGuide calculator on the same page, it's fine to paste this exact block for each one, no changes needed. In WordPress specifically: add a Custom HTML block to your page, paste the code above into it, and publish. That's it, no account, no API key, and no plugin needed.
Check the tin, most pellets list weight in grains right on the packaging. If it's gone, manufacturer spec sheets online almost always list it by pellet name and caliber.
Indirectly, yes. A longer barrel generally lets a pellet accelerate longer before leaving the muzzle, which can mean higher velocity, and therefore higher FPE, from the same power plant.
Box labels are usually measured with a specific lightweight pellet under ideal conditions. Your actual FPE will vary with the pellet you shoot, so always calculate using your own chronographed velocity, not the advertised figure.