Pool Gallons Calculator
Enter all dimensions in feet. For sloped pools, add shallow and deep depth to calculate average depth automatically.
How to find out how many gallons your pool holds
Knowing your pool volume is one of the most important numbers for pool care. If you overestimate or underestimate gallons, chemical dosing becomes guesswork. This calculator helps you estimate pool water volume quickly for rectangular, round, oval, and freeform pools.
The result gives you an estimated gallon count and liters. Use that number as your baseline for chlorine additions, pH balancing, algaecide, stabilizer, and salt calculations.
Why pool gallons matter
- Chemical dosing: Most product labels dose per 10,000 gallons.
- Salt systems: Salt concentration requires an accurate water volume estimate.
- Heating costs: More gallons means more energy required to raise water temperature.
- Pump run time: Turnover planning depends on total pool volume.
- Water replacement: During draining/refilling, gallons help estimate cost and timing.
Pool gallon formulas by shape
1) Rectangular or square pool
Gallons = Length × Width × Average Depth × 7.48052
Measure length and width in feet. For average depth, use: (shallow depth + deep depth) ÷ 2.
2) Round pool
Gallons = π × (Diameter ÷ 2)² × Average Depth × 7.48052
If you only know radius, use radius directly instead of diameter.
3) Oval pool
Gallons = π × (Length ÷ 2) × (Width ÷ 2) × Average Depth × 7.48052
This treats the top surface like an ellipse, which is usually a good estimate for standard oval pools.
4) Freeform pool (area known)
Gallons = Surface Area × Average Depth × 7.48052
If your pool builder provided square footage, this method is usually the most direct path.
How to measure your pool accurately
- Use a tape measure and measure to the nearest inch if possible.
- Take multiple depth readings (shallow, transition, deep) on sloped pools.
- For freeform pools, use a builder plan or mapping app for surface area.
- Re-check measurements before buying chemicals in bulk.
Examples
Example A: Rectangle
A pool is 30 ft long, 15 ft wide, with 3.5 ft shallow and 7.5 ft deep end. Average depth is 5.5 ft. Estimated volume: about 18,514 gallons.
Example B: Round
A round above-ground pool has a 24 ft diameter and 4.5 ft average depth. Estimated volume: about 15,229 gallons.
Example C: Oval
An oval pool measures 32 ft by 16 ft, with 5 ft average depth. Estimated volume: about 15,041 gallons.
Common mistakes to avoid
- Using maximum depth instead of average depth.
- Mixing feet and inches without converting.
- Rounding dimensions too aggressively.
- Ignoring steps, benches, or tanning ledges in detailed calculations.
- Assuming every pool with curved corners is a perfect rectangle.
Quick FAQ
Is this an exact number?
It is an estimate. For most maintenance tasks, this estimate is accurate enough. For precision dosing, you can fine-tune over time based on test results.
What if my deep end is much larger than the shallow end?
Use more depth readings and calculate a weighted average if needed. The simple average is great for many pools, but unusual profiles may need a custom calculation.
Should I use gallons or liters?
In the U.S., most chemical labels use gallons. International products may use liters or cubic meters. This calculator returns gallons and liters so you can work either way.
Final tip
Save your calculated volume in your pool maintenance notes. Once you lock in an accurate gallon value, balancing chlorine, pH, alkalinity, and stabilizer becomes faster and more consistent.