Pool volume calculator
Every chemical dose starts with how many gallons you have. Pick your shape, enter the measurements, and use the result across every calculator on this site.
Your pool holds
Fill time
– hours to fill from empty (– days of running the hose).
Why “shallow + deep ÷ 2” can be wrong
The average-depth shortcut assumes the floor slopes evenly from end to end. Many in-ground pools instead have a long flat shallow area and a slope only near the deep end. Drag the sliders and watch the two answers split apart.
Shortcut average: 5.5 ft
True average: 4.25 ft — the shortcut is 29% high.
If your pool looks like the steep version, split it into a flat shallow rectangle and a sloped deep section, work out each with the calculator and add them.
Pool volume formulas
| Shape | Gallons (feet) |
|---|---|
| Rectangle | L × W × avg depth × 7.48 |
| Round | 3.14 × (diameter ÷ 2)² × depth × 7.48 |
| Oval | 3.14 × (L ÷ 2) × (W ÷ 2) × depth × 7.48 |
| Kidney | 0.45 × (A + B) × L × depth × 7.48 |
| Freeform | surface area × avg depth × 7.48 |
In meters, length × width × depth gives cubic meters; multiply by 1,000 for liters. One cubic foot is 7.48 US gallons and one US gallon is 3.785 liters.
Measure the water, not the wall
Above-ground pools are sold by wall height, but water normally sits 4–6 inches below the top rail. Measuring the real water depth can change the answer by 10% or more.
Common above-ground sizes
| Round pool | At 48 in water |
|---|---|
| 12 ft | 3,400 gal |
| 15 ft | 5,300 gal |
| 18 ft | 7,600 gal |
| 21 ft | 10,400 gal |
| 24 ft | 13,500 gal |
| 27 ft | 17,100 gal |
| 30 ft | 21,200 gal |
Questions pool owners ask
How do I calculate how many gallons are in my pool?
Multiply length × width × average depth (all in feet) and then by 7.48, the number of gallons in one cubic foot. For a round pool use 3.14 × radius² × depth × 7.48. Average depth is the shallow-end depth plus the deep-end depth, divided by two.
How do I find average depth for a pool with a deep end?
Add the shallow-end depth and the deep-end depth and divide by two. That works when the floor slopes evenly. If the pool has a long flat shallow section and a short hopper, split it into two rectangles and add their volumes.
How many gallons is a 24 ft round above-ground pool?
A 24 ft round pool filled to 4.5 ft (54 in wall filled to about 48–52 in) holds roughly 13,000–15,000 gallons. Water level is usually 6 inches below the top of the wall, so measure the actual water depth.
What is the most accurate way to measure pool volume?
Read the water meter before and after filling, or use a salt or CYA test before and after a known dose. Measuring shape gets you within about 10%, which is fine for dosing if you add chemicals in stages and retest.
How long does it take to fill a pool with a garden hose?
A typical 5/8 inch garden hose delivers about 9–12 gallons per minute. A 15,000 gallon pool at 10 gpm takes 25 hours. Check your flow by timing how long it takes to fill a 5 gallon bucket.