The calculator's dimensions are: 21.3 x 87.5 x 180.5mm A 1U rack comes in various depths, let's assume 1m (1000mm), and the width between rails is about 450mm.

The calculator's dimensions are: 21.3 x 87.5 x 180.5mm A 1U rack comes in various depths, let's assume 1m (1000mm), and the width between rails is about 450mm. 1U is around 44mm in height. So in 1U, you could stack them 2 high, 5 wide, and 5 deep (this leaves a little wiggle room for cables and such), or 50 per 1U, or 2100 in a 42U full rack.