Pool Volume
This free pool volume calculator estimates how many gallons of water a rectangular, round, or oval pool holds, from its dimensions and average depth. Use the result with your chemical product's own label instructions for dosing. Nothing you enter is sent anywhere or stored.
How to Use It
- Select your pool shape: Rectangular, Round, or Oval.
- Enter the pool's dimensions (length and width, or diameter for a round pool).
- Enter the average depth. For a sloped pool, add the shallow and deep depths and divide by 2.
- The estimated gallons update instantly, no submit button.
How It Works
This calculator first finds the pool's surface area from its shape and dimensions, then multiplies by the average depth to get the volume in cubic feet, then converts cubic feet to gallons. That conversion factor is fixed: one cubic foot of water always holds about 7.48 gallons, since a US gallon is defined as 231 cubic inches and a cubic foot is 1,728 cubic inches.
Formulas
rectangular: gallons = length × width × average depth × 7.48
round: gallons = pi × (diameter ÷ 2)² × average depth × 7.48
oval: gallons = pi × (length ÷ 2) × (width ÷ 2) × average depth × 7.48
A worked example: a rectangular pool 32 feet by 16 feet with a 5 foot average depth has 2,560 cubic feet of water, which comes out to about 19,150 gallons. A round pool 24 feet across with a 4.5 foot average depth works out to about 15,228 gallons.
Everything runs client-side in your browser. Nothing you enter is sent anywhere or stored.
Frequently Asked Questions
What does this calculator actually give me, and what do I do with it?
This calculator estimates how many gallons of water your pool holds. It does not calculate chemical amounts, since that depends on the specific chlorine, shock, or other product you are using and its own concentration. Once you know the gallons, check that product's label for how much to add per gallon or per thousand gallons.
How do I find the average depth of a pool that slopes from shallow to deep?
Add the shallow end depth and the deep end depth, then divide by 2. A pool that is 3 feet deep at the shallow end and 7 feet deep at the deep end has an average depth of 5 feet, assuming the floor slopes at a fairly constant rate between the two ends. If your pool has a shallow, flat section before the slope begins, this average will run slightly high, since it assumes the slope starts right at the shallow end.
Why is an oval pool not just the average of round and rectangular?
An oval pool's surface area comes from the ellipse area formula, pi times half the length times half the width, not a simple average of a rectangle and a circle with the same outer dimensions. A 20 by 12 foot oval actually holds noticeably less water than a 20 by 12 foot rectangle, since the ellipse formula accounts for the pool's curved sides cutting into that rectangular footprint.
Does the pool shape affect the gallons-per-cubic-foot conversion?
No. One cubic foot of water is always about 7.48 gallons, regardless of the container shape. What changes between shapes is how the surface area is calculated (length times width for rectangular, pi times radius squared for round, the ellipse formula for oval), not the conversion from cubic feet to gallons.
Can you give a worked example for each shape?
A rectangular pool, 32 feet by 16 feet with a 5 foot average depth, holds about 19,150 gallons. A round pool, 24 feet across with a 4.5 foot average depth, holds about 15,228 gallons. An oval pool, 20 feet by 12 feet with a 5 foot average depth, holds about 7,050 gallons, noticeably less than a rectangular pool with the same outer length and width.