Pool Volume Calculator
Knowing your pool's volume in gallons is the first step to dosing chemicals correctly, sizing a pump or heater, and running an effective green-to-clean. Pick your pool shape, enter the dimensions, and we'll estimate the total volume in gallons and liters.
For a pool with a single, even depth, enter the same value in both depth fields.
Enter your pool dimensions to estimate its volume.
How the calculation works
The calculator multiplies your pool's surface area by its average depth to get the total volume, then converts that figure into gallons and liters. There are 7.48 gallons in every cubic foot of water.
- Rectangular: length × width × average depth × 7.48
- Round: π × radius² × average depth × 7.48
- Oval: π × (length / 2) × (width / 2) × average depth × 7.48
Worked examples
Seeing the math with real numbers makes it click:
- 16 × 32 ft rectangle, 3 ft shallow to 8 ft deep (avg 5.5 ft): 16 × 32 × 5.5 × 7.48 ≈ 21,000 gallons.
- 18 ft round, even 4 ft water depth: 3.14 × 9 × 9 × 4 × 7.48 ≈ 7,600 gallons.
- 15 ft × 30 ft oval, avg 4.5 ft: 3.14 × 7.5 × 15 × 4.5 × 7.48 ≈ 11,900 gallons.
How to measure your pool correctly
A common mistake throws the whole estimate off: measuring the wall height instead of the water depth. Always measure to the actual water line.
- Measure the water, not the wall. A 52-inch wall filled to 46 inches is a 46-inch (about 3.8 ft) depth.
- Find average depth for pools that slope: (shallow depth + deep depth) ÷ 2. If your pool has one even depth, enter that same number in both depth fields above.
- Converting inches to feet: multiply inches by 0.0833. So 9 inches = 9 × 0.0833 ≈ 0.75 ft, making 25 ft 9 in = 25.75 ft.
Kidney & irregular-shaped pools
Free-form and kidney pools don't fit one formula. Two approaches work:
- Split and add: break the pool into rectangles and circles, calculate each with the tool above, and add the results together.
- Kidney shortcut: 0.45 × (width A + width B) × length × average depth × 7.48, where A and B are the widest and narrowest widths.
Common pool sizes and gallons
Rough estimates to sanity-check your result (actual volume depends on your exact depth):
| Pool size | Approx. water depth | Estimated gallons |
|---|---|---|
| 12 ft round | 4 ft | ~3,400 |
| 15 ft round | 4 ft | ~5,000 |
| 24 ft round | 4 ft | ~13,500 |
| 12 × 24 ft rectangle | avg 5 ft | ~10,800 |
| 16 × 32 ft rectangle | avg 5.5 ft | ~21,000 |
| 20 × 40 ft rectangle | avg 6 ft | ~36,000 |
Why your pool volume matters
Volume is the number every other pool calculation depends on. Once you have it, put it to work:
- Get exact chemical doses with the Chemistry Calculator.
- Work out chlorine or shock amounts with the Chlorine Calculator.
- Size a saltwater dose with the Salt Calculator, or stabilizer with the Stabilizer (CYA) Calculator.
- Estimate running costs with the Pump Cost Calculator.
- New to the terms? Start at Pool School.
Frequently asked questions
How do I calculate how many gallons are in my pool?
Multiply the pool's surface area by its average depth to get the volume in cubic feet, then multiply by 7.48 to convert to US gallons. For a rectangular pool: length × width × average depth × 7.48. The calculator above does this for you for rectangular, round, and oval pools.
What is the average depth of my pool?
Average depth is the shallow-end depth plus the deep-end depth, divided by two. For example, a pool that is 3 ft at the shallow end and 8 ft at the deep end has an average depth of (3 + 8) / 2 = 5.5 ft. Measure the depth of the water, not the height of the wall.
How many gallons is a 15 ft round above-ground pool?
A 15 ft round pool with a 48-inch (4 ft) water depth holds roughly 5,000 gallons. Deeper 52-inch walls hold a bit more. Use the calculator with your exact diameter and water depth for a precise figure.
How do I calculate volume for a kidney or irregular-shaped pool?
Break the pool into simpler shapes (rectangles and circles), calculate each one's volume, and add them together. For a kidney shape, a common shortcut is: 0.45 × (widest width + narrowest width) × length × average depth × 7.48 gallons.
Why does knowing my pool volume matter?
Volume determines how much of every chemical to add. Dose based on the wrong volume and you'll under- or over-treat the water. It also drives correct pump and heater sizing and filter turnover. It's the first number you need before using any other pool calculator.
These are close estimates. Irregular shapes, tanning ledges, and steps can shift the real figure slightly, so round to the nearest few hundred gallons when dosing chemicals.