How this instrument works
Bean bag chairs aren't actually filled with beans — they're filled with small expanded polystyrene (EPS) foam pellets, the same lightweight, springy material used in packing peanuts, just cut to a smaller, rounder pellet size for seating comfort. Because EPS pellets are mostly trapped air, a given volume of them weighs surprisingly little compared to an equal volume of almost anything else you'd stuff a cushion with.
This calculator treats a bean bag as a simple rectangular volume — length times width times height — then converts that volume to a filler weight using an assumed EPS bean-bag-filler density of 20 kg per cubic meter, a widely-used industry rule of thumb for this specific application. Dividing the total filler weight by however much filler comes in one package of the product you're buying gives the number of packages you'll need.
Real bean bags aren't perfect rectangular boxes — they're rounded, irregularly shaped, and settle unevenly once filled — so treating length x width x height as the volume is a deliberate simplification, not a precise geometric measurement of the actual finished shape. It gives a reliable estimate for shopping-list purposes; buy slightly more filler than the raw calculation suggests if you want the bag genuinely full rather than under-stuffed after the pellets settle.
- Enter Length, Width, and Height in meters for the bean bag or cushion you're filling.
- Enter Filler weight per package — check the packaging of the EPS beads you're buying.
- Read Volume (m³) — the simple box-volume estimate from your three dimensions.
- Read Filler needed (kg) — volume scaled by the assumed 20 kg/m³ EPS filler density.
- Read Packages of filler needed, and consider rounding up and buying a bit extra to account for settling and an imperfect rectangular shape.
Worked example — a 1.0 × 0.9 × 0.8 m bean bag chair
A standard bean bag chair measuring 1.0 m x 0.9 m x 0.8 m has a box-volume of 0.72 m³. At the assumed 20 kg/m³ EPS filler density, that's 0.72 x 20 = 14.4 kg of filler needed. If your filler comes in 0.5 kg packages, that's 14.4 ÷ 0.5 = 28.8 packages — round up to 29 to be safe.
A much larger 1.5 x 1.2 x 0.3 m floor cushion has a smaller volume despite its larger footprint, because it's flatter: 0.54 m³, needing 10.8 kg of filler — for example, 10.8 packages if the filler comes in 1 kg bags.
Questions
Why 20 kg per cubic meter specifically?
That figure is a widely-used industry assumption for the density of expanded polystyrene beads once they're loosely packed inside a bean bag, reflecting how much air remains trapped between the pellets even when compressed by someone sitting on the bag. Different brands' bead sizes can shift this slightly, but 20 kg/m³ is a solid general-purpose estimate for shopping-list planning.
Should I buy exactly the calculated amount of filler, or more?
Buy a bit more than the raw calculation if you want the bag genuinely full and firm — EPS beads settle and compress somewhat over the first weeks of use, and a bag filled to the exact calculated volume often feels slightly under-stuffed once that settling happens. Rounding the package count up rather than down is the safer default.
Does treating the bean bag as a rectangular box overestimate or underestimate the filler needed?
It's a reasonable middle-ground approximation rather than a systematic over- or under-estimate — real bean bags are rounder and less voluminous than a perfect box of the same length/width/height, but they also puff outward past their 'resting' dimensions once filled and sat in. Treat the box-volume estimate as a solid starting point, not a guaranteed exact fill amount.
Can I use this for other EPS-filled items, like pet beds or floor cushions?
Yes — the same box-volume-times-density approach works for any roughly rectangular EPS-filled item, not just chair-style bean bags. Measure the item's length, width, and height the same way, and the filler-weight estimate follows the identical formula.
What if my filler comes in liters or cubic feet instead of kilograms?
Convert to kilograms first, or convert the volume output to your filler's stated unit before dividing — this calculator's package count assumes both the filler-weight output and your package size are measured in the same unit (kilograms), so mixing units without converting will give a meaningless result.