The number of water beads you need to fill your desired area depends on the size of your water beads and the area which is being filled. The standard water bead size is between 9 and 11mm after growing (with 10mm being the average), and this is the size that we will use in this article.
If you're using different sized water beads then you will have to estimate the number you require (go with less if your beads are bigger, and a more if you've got smaller beads).
Some useful estimates:
- Standard measuring cup (240ml): 100 water beads
- Standard 2L bottle (2000ml): 830 water beads
- Standard bathtub (302 litres): 125840 water beads
If you decide to add a little bit of salt or rubbing alcohol to your water beads (to make them last longer and stave off mould) then be aware that your beads will not grow quite as large and therefore you will need more beads to fill the same area.