Dry Box Sizing Calculator for 3D Printing
Find the right airtight container size for your filament spools.
Enter spool count and size to get minimum box dimensions, volume, and desiccant quantity.
A dry box is an airtight container — typically a food storage bin or clip-top box — loaded with silica gel desiccant to keep filament dry during both storage and printing. Getting the size right matters: too small and spools don’t fit or the desiccant gets crowded; too large and a small desiccant pack gets overwhelmed by the extra air volume.
Standard spool dimensions. A typical 1 kg spool has an outer diameter around 200 mm and a width of 55-70 mm. The spool hub (inner hole) is typically 52 mm. Some brands run narrower or wider, but 200 x 65 mm covers most 1 kg and 500 g spools. A 2 kg spool is usually the same OD but ~80-90 mm wide. A 2.5 kg or 3 kg spool can be 250-300 mm OD.
Storage orientation options:
- Upright (spool standing like a wheel): needs a box at least as tall as the OD. Spools line up side by side, which usually means a wide shallow box.
- Flat (spool lying face-down): needs a box at least as wide and deep as the OD. Spools can stack, so box height = width × number of spools.
Desiccant sizing. A rough rule: 100 g of silica gel per 5-7 liters of container volume. Rechargeable silica gel with a color indicator (orange or blue beads) is easiest to manage. Replace or regenerate when the beads change color.
Minimum clearance. Add at least 10 mm on each side of the spool for handling clearance. Tight boxes make loading awkward and risk damaging the filament.
Common container sizes to look for: Sterilite 6-qt (5.7 L), IRIS 19 L (holds 4-5 spools upright), Husky 27 L, and the IKEA SAMLA range. The calculator recommends which size class suits your spool count.