Enter a pellet's weight in grains and its caliber to get sectional density (SD), calculated live as you type. Switch to Compare to check SD across a few pellets side by side.
Sectional density compares a pellet's weight to its cross-sectional area, in effect asking how much mass is packed behind a given diameter. A pellet with a higher SD carries its weight through a smaller frontal area, which generally means it resists slowing down and holds energy better over distance and through resistance like fur, hide, or wind. It's not a full replacement for ballistic coefficient, which also accounts for the pellet's shape, but SD is the simple, exact half of that picture and is often used as a quick reference on its own.
Ballistic coefficient (BC) combines sectional density with a shape-based form factor, requiring either the manufacturer's published figure or a chronograph measurement over a known distance to estimate. Sectional density skips the shape factor entirely, it's pure algebra from weight and diameter, so it's exact rather than estimated. That makes it a useful, no-chronograph-needed starting point when comparing pellets of the same or similar shape, particularly within one caliber.
Switch the calculator above to Compare to check sectional density across a few pellets at once, useful when you're deciding between pellet weights within a caliber, or comparing across calibers using the Custom diameter option. Add up to four pellets side by side.
Typical airgun pellet SD values run roughly from the low 0.01s for light, short pellets up to around 0.03–0.04 for heavy, longer pellets in the same caliber. Higher generally means better penetration and less wind drift for a given caliber, all else being equal, but shot placement and pellet construction still matter more than SD alone for any real-world outcome.
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 id="airgunguide-sd-embed" src="https://airgunguide.com/embed/airgun-sd-calculator.html" width="100%" height="590" style="border:1px solid #c9c0a5;max-width:420px;" title="Airgun Sectional Density Calculator"></iframe>
<script>
(function(){
window.addEventListener('message', function(e){
if(!e.data || e.data.type !== 'airgunguide-embed-resize' || e.data.embedId !== 'airgunguide-sd'){ return; }
var f = document.getElementById('airgunguide-sd-embed');
if(f){ f.style.height = e.data.height + 'px'; }
});
})();
</script>The small script after the iframe lets the calculator resize itself automatically as you switch modes or add pellets, so it never shows an internal scrollbar. 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.