How Many Orbeez Does It Take to Fill a Bathtub?

Key Takeaways

To fill a standard U.S. bathtub, which holds 42 gallons (159 liters) of water, you would need approximately 67,200 fully hydrated Orbeez.
The cost to fill a bathtub with Orbeez could be significant, nearly $24 for a package of 2,000 Orbeez, making the total cost for the necessary 67,200 Orbeez around $800.
If you plan to submerge yourself in the tub filled with Orbeez, you will displace some of the beads, reducing the number needed to about 48,000 Orbeez for around 30 gallons (114 liters) to accommodate the displacement.

In the year 2020, people likely spent more time bored at home than in any other year since the turn of the century. And it's entirely possible that millions of homebound people actually considered performing the following task:

Discover through the scientific method of experimentation how many hydrated Orbeez it takes to fill your bathtub.

While we applaud experiments of most kinds, we will do that math for you here so you don't have to ruin your plumbing finding out. Unless, of course, you want to.

Orbeez start off as hard, colorful little beads about the size of ball bearings made of polymers composed of acrylic acid, sodium hydroxide and water — the same stuff that makes diapers and maxi pads absorbent. When submerged in water, the spaces between these polymers are packed full of water molecules, resulting in their swelling to a size over orbeez">150 times their original diameter. They also can be dehydrated — just set them in the sun or in a dry, open container — whereupon they shrink back to their original size in a day or so.

So, how many of these water beads would it take to fill up the bathtub at your house?

Bathtub sizes differ, but in the U.S. a standard tub holds 42 gallons (159 liters) of water. How many individual water beads would it take to fill an entire tub?

According to the Orbeez website, 100 dried water beads yield one cup (240 milliliters) of fully hydrated Orbeez. There are 16 cups in a gallon, and therefore 1,600 water beads in a gallon. So, for a 42-gallon (159-liter) tub you'll need 67,200 water beads to fill a standard sized bathtub. But, be aware, that at nearly $24 for a package of 2,000 Orbeez, it could cost you a pretty penny to fill your bathtub. There are, of course, similar, less expensive options on the market as well.

But wait! If you're really going to try this at home, remember that if you are planning to submerge yourself in the tub full of Orbeez, you'll displace a ton of swollen beads with your body, so maybe shoot for around 30 gallons (114 liters) to be safe. In that case, you'll need more like 48,000 water beads. Point being, if you get in your Orbeez bath, you may not get any cleaner, but it will save you some money.

Final caveat: Orbeez grow bigger if you use distilled water. The salts and minerals in tap water inhibit the growth of each bead, and some people put salt or rubbing alcohol in their beads to keep them from growing bacteria, which also keeps them from growing as large. For the biggest beads, use distilled water!

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