Knowing how many gallons of water are in your pool is important for determining things like the right amount of chemicals to add, heater size, and so many other decisions. Use our calculator below to get started.
Pool Volume Calculation Basics
There are a few basic metrics that you need to calculate the volume of your pool.
- Pi (3.14 constant)
Multiplying length and width of your pool gives you the surface area that it occupies. Throw depth into the equation and you start getting to basic volume calculations. Make sense? Okay, let’s jump into more specifics for different pool shapes.
Rectangular Pool Volume
Determining the volume of a rectangular pool is pretty straightforward, but your calculation will vary slightly depending on the slope of the bottom of your pool.
If your pool has a constant depth across the bottom, you’ll determine the surface area of the pool (length x width), multiply that by the depth of the pool, then multiply by 7.5 to calculate the volume in gallons.
Length x width x depth x 7.5 = volume (gallons)
However, many pools aren’t that simple – you have a shallow end and a deep end. To determine the volume of a pool with variable depths, you need to calculate the average depth of the pool. Do this by adding the the shallow end to the deep end and dividing by 2.
(shallow depth + deep depth) / 2 = average depth
From there, the equation is similar to our constant depth example.
Length x width x average depth x 7.5 = volume (gallons)
Alright, let’s move on to round pools.
Round Pool Volume
For round pools, you need to start by getting the full diameter of the pool. Divide that diameter by 2 to get the radius of the pool. After you get the radius and depth, plug those into the formula below.
3.14 × radius2 × depth × 7.5 = volume (gallons)
Pretty simple! However, not all pools are simple rectangles and circles.
What About Freeform Swimming Pools?
Irregularly shaped (freeform) pools are super popular and a lot of fun from a design perspective, but can be a bit of a headache when calculating pool water volume. To solve this problem, break your pool dimensions down into smaller regular chunks. If your pool is kidney-shaped, break it down into two circles. From there, use the calculator above to determine the volume of the two halves and then add them together to get the full volume of the pool.