A Kallax cube is a tight brief: the opening is only about 33 cm square, so most “large” storage boxes will not go in at all, and anything that does fit tends to leave a stripe of wasted height. The trick is to find a footprint that slides in with a few millimetres to spare and then stack it to the top.
Two things to check before you buy:
- Depth is your friend. The cube is deeper than it is wide, so a box that is longer than 33 cm can still fit if it goes in end-on. The results below already account for that.
- Lids need a little headroom. Stacked boxes only need clearance at the top of the cube, but you need to be able to lift the top box’s lid without pulling everything out. If that matters, take 20 mm off the height in the calculator.
One thing to know before the results: no Really Useful Box fits flush. Their shortest side is 395 mm and the cube is about 390 mm deep, so they stick out by a finger’s width. The IKEA boxes below are made for the cube, and IKEA’s SAMLA is the one to pick if you want a lid.
The results are worked out from the box sizes in our catalogue for a 33 × 39 × 33 cm opening. Open it in the calculator to change the size or see it in 3D.