Online Calculator - How many balls for a dry pool?

Are you planning to buy a dry pool and wondering if 200 balls will be enough for your child to “dive” into? Or maybe you’re worried that if you order too many, you won’t be able to close the door to the room?

Don’t worry—you don’t need to dig up those high school formulas for the volume of solids. Our online calculator will do it for you in seconds. In this guide, you’ll learn how to enter accurate data so your result is spot on.

Dry Pool Ball Calculator

How do you calculate the number of balls?

The math behind the calculator is based on simple geometric shapes, but it takes into account what is known as the “fill factor.” The balls are round, so there is always a little bit of empty space (air) between them.

Square (rectangular) pool

The calculator uses the formula for the volume of a cylinder. If you want to calculate it by hand, remember to square the radius and multiply it by $\pi \approx 3.14$. But why bother, when our calculator can do it flawlessly for you?

Square and rectangular pools

Here, it’s as simple as can be: just multiply the length by the width and the planned height of the fill. These are the most common shapes, and they’re the easiest to fill precisely.

A swimming pool with irregular
and unusual shapes

Do you have a heart-shaped, corner (quarter-circle), or polygonal pool?

Corner pool – calculate it as 1/4 of a round pool.
Irregular shapes – try to “fit” them into the nearest rectangle. The result will be approximate, but usually good enough to avoid a major mistake.

How many balls should be in the pool?

Before you confirm your answer, consider the child’s age and the purpose of the pool. Use the guide below:

1/3 of the height – best for infants (must be supervised)
Half the height – for toddlers (ages 1–3) – children can easily “bury” themselves in the balls without scattering them too much outside the pool area
3/4 height – older kids (3+ years) – maximum fun, perfect for jumping and diving

Important note: Never fill the pool to the brim. When a child gets in, their body weight will push the balls upward—the “empty pool” effect will disappear in an instant!

How to verify the result in practice

Did the calculator give you a result like 345 balls? Keep in mind that balls are usually sold in packs of 50, 100, or 200.

Round up: It’s better to have 20 extra balls on hand (some might get squashed or “lost” under the couch) than to end up with an empty pool.
Check for flexibility: If your pool is made of soft foam, it may expand slightly under the weight of the balls and your child, which will increase the amount of water needed to fill it.
“First dip” test: After pouring in the beads, let your child get inside. If you can still see through the bottom after your child gets in, you should buy another bag (50 beads).

With our calculator, you’ll avoid the frustration and extra shipping costs of having to reorder missing items. Have fun!