How to Calculate Swimming Pool Volume
A practical guide to calculating swimming pool volume in gallons, liters, and cubic feet, with formulas for every pool shape.
Last updated: 2025-03-15
Why Knowing Your Pool Volume Matters
Knowing the exact volume of your swimming pool is essential for proper chemical treatment, heating calculations, and water cost estimates. Under-dosing chemicals leaves the pool unsanitary; over-dosing wastes money and can irritate skin and eyes. The volume also determines how long your pump and filter need to run for a complete turnover.
Key Conversion Factors
- 1 cubic foot = 7.48052 US gallons = 28.3168 liters
- 1 US gallon = 3.78541 liters
- 1 cubic meter = 264.172 US gallons = 1,000 liters
- 1 cubic yard = 201.974 US gallons
Rectangular Pool Formula
Volume (gallons) = Length (ft) × Width (ft) × Average Depth (ft) × 7.48052
For the average depth, add the shallow end depth to the deep end depth and divide by 2.
Circular Pool Formula
Volume (gallons) = π × Radius² (ft) × Average Depth (ft) × 7.48052
Or equivalently: Diameter² × Average Depth × 5.9.
Oval Pool Formula
Volume (gallons) = Long Diameter (ft) × Short Diameter (ft) × Average Depth (ft) × 5.9
Worked Examples
Example 1: Rectangular pool (30 ft × 15 ft, shallow 3 ft, deep 8 ft)
- Step 1: Average depth = (3 + 8) / 2 = 5.5 ft.
- Step 2: Volume = 30 × 15 × 5.5 = 2,475 cubic feet.
- Step 3: Gallons = 2,475 × 7.48052 = 18,514 gallons.
- Step 4: Liters = 18,514 × 3.785 = 70,076 liters.
Example 2: Circular above-ground pool (18 ft diameter, 4 ft deep)
- Step 1: Radius = 9 ft.
- Step 2: Volume = π × 9² × 4 = 1,017.88 cubic feet.
- Step 3: Gallons = 1,017.88 × 7.48052 = 7,614 gallons.
Example 3: Olympic-size pool (50 m × 25 m × 2 m deep)
- Step 1: Volume = 50 × 25 × 2 = 2,500 cubic meters.
- Step 2: Liters = 2,500 × 1,000 = 2,500,000 liters.
- Step 3: Gallons = 2,500 × 264.172 = 660,430 gallons.
Use our volume converter to convert between gallons, liters, and cubic feet.
Quick Reference Table: Common Pool Sizes
| Pool Size | Avg Depth | Gallons | Liters |
|---|---|---|---|
| 12 × 24 ft rect | 5 ft | 10,800 | 40,880 |
| 16 × 32 ft rect | 5 ft | 19,200 | 72,670 |
| 20 × 40 ft rect | 5.5 ft | 33,000 | 124,900 |
| 15 ft round | 4 ft | 5,300 | 20,060 |
| 18 ft round | 4 ft | 7,600 | 28,770 |
| 24 ft round | 4 ft | 13,500 | 51,100 |
Real-World Applications
Chemical Dosing
Most pool chemicals are dosed per 10,000 gallons. If your pool holds 18,500 gallons, you would use 1.85 times the dose listed for 10,000 gallons. Accurate volume calculations prevent under- or over-treatment.
Heating Costs
It takes approximately 8.34 BTUs to raise one gallon of water by 1 °F. For an 18,500-gallon pool, heating the water by 10 °F requires about 1,543,000 BTUs. This helps you estimate energy costs and choose the right heater size. Learn more in our BTU guide.
Water Costs
Filling a pool requires a known volume. If your water utility charges per 1,000 gallons, knowing your pool holds 18,500 gallons lets you estimate the cost before filling. Evaporation typically loses 1/4 to 1/2 inch of water per day, which can also be calculated using pool surface area.
Frequently Asked Questions
How do I calculate the volume of a rectangular pool?
Multiply Length × Width × Average Depth to get cubic feet, then multiply by 7.48052 to convert to US gallons.
How many gallons are in a typical swimming pool?
A typical residential swimming pool holds between 10,000 and 30,000 gallons (38,000 to 114,000 liters). An Olympic pool holds about 660,000 gallons (2.5 million liters).
How many gallons are in one cubic foot of water?
There are 7.48052 US gallons in one cubic foot of water.
How do I calculate the average depth of a pool?
For a pool with a uniform slope, add the shallow depth and deep depth together and divide by 2. For example, (3 ft + 8 ft) / 2 = 5.5 ft average depth.