Pool Volume Calculator - Calculate Gallons of Water in Your Pool
Calculate how many gallons of water your swimming pool holds with our free pool volume calculator. Enter your pool's dimensions to get results in gallons, liters, cubic feet, and cubic yards.
Results:
Tip: For pools with a shallow end and deep end, use the average depth (add shallow + deep, divide by 2). Depth is measured in inches by default for pools.
How to Use the Pool Volume Calculator
This calculator offers two ways to find your pool's water volume:
Option 1: By Dimensions
Enter the length, width, and average depth of your pool. This works best for rectangular and square pools. For pools with varying depth, use the average depth (shallow end + deep end ÷ 2).
Option 2: By Area
If you already know the surface area of your pool in square feet, enter it along with the average depth. This is useful for irregularly shaped pools where you've already calculated the surface area.
How Many Gallons of Water Are in My Pool?
The volume depends on three factors: 1. Pool shape — rectangular, round, oval, or freeform 2. Surface area — length × width (or calculated from diameter) 3. Average depth — the average of shallow and deep end depths
Quick Formulas by Pool Shape
Rectangular Pool: Length × Width × Average Depth × 7.48 = gallons
Round Pool: Diameter × Diameter × Average Depth × 5.9 = gallons
Oval Pool: Long Diameter × Short Diameter × Average Depth × 5.9 = gallons
Common Pool Sizes and Their Volumes
Here are typical volumes for standard pool sizes (assuming 5 ft average depth):
- 12 × 24 ft — 10,771 gallons
- 14 × 28 ft — 14,697 gallons
- 16 × 32 ft — 19,200 gallons
- 18 × 36 ft — 24,300 gallons
- 20 × 40 ft — 29,920 gallons
- 15 ft round — 6,600 gallons
- 18 ft round — 9,529 gallons
- 24 ft round — 16,942 gallons
- 27 ft round — 21,429 gallons
Why You Need to Know Your Pool Volume
Knowing how many gallons your pool holds is essential for:
- Chemical treatment — chlorine, pH adjusters, algaecides, and shock treatments are all dosed based on pool volume in gallons
- Heating costs — estimate energy needed to heat your pool
- Water bills — know how much it costs to fill or top off your pool
- Filter sizing — ensure your pump and filter are rated for your pool volume
- Salt systems — salt chlorine generators require a specific salt-to-water ratio
How to Measure Your Pool
Step 1: Measure Length and Width
Use a tape measure along the longest and widest points of your pool. Measure in feet.
Step 2: Measure Depth
- Constant depth: Measure at any point
- Variable depth: Measure the shallow end and deep end, then average them
- Example: 3 ft shallow + 8 ft deep = 5.5 ft average depth
Step 3: Calculate
Enter the measurements into the calculator above. The tool converts everything to gallons automatically.
Understanding Pool Water Volume
Gallons per Cubic Foot
One cubic foot of water contains 7.48 gallons. This is the conversion factor used in all pool volume calculations.
Weight of Water
Water weighs 8.34 pounds per gallon. A typical 20,000-gallon pool contains over 166,000 pounds of water — that's about 83 tons.
Fill Time
A standard garden hose delivers about 9 gallons per minute (540 gallons per hour). At that rate: - 10,000 gallons — about 18.5 hours - 20,000 gallons — about 37 hours - 30,000 gallons — about 55.5 hours
Pool Chemical Dosing Guide
Once you know your pool volume, use these general guidelines (always follow product label instructions):
| Chemical | Dosage per 10,000 gallons |
|---|---|
| Chlorine (liquid) | 52 oz to raise 1 ppm |
| pH Increaser | 6 oz to raise 0.2 |
| pH Decreaser | 12 oz to lower 0.2 |
| Pool Shock | 1 lb per 10,000 gal |
| Algaecide | Follow product label |
Tips for Pool Maintenance
- Test water weekly — use test strips or a liquid test kit to check chlorine, pH, and alkalinity
- Keep records — log your pool volume and chemical additions
- Account for water loss — evaporation and splash-out reduce volume over time
- Winterize properly — know your volume for antifreeze and winter chemical dosing
- Recalculate after renovations — if you change the depth or shape, recalculate your volume
Frequently Asked Questions
How do I calculate gallons in an irregularly shaped pool?
Break your pool into simpler shapes (rectangles, circles), calculate each section's volume separately, then add them together. Or measure the surface area directly and multiply by average depth × 7.48.
What if my pool has a hopper bottom?
For pools with a hopper or bowl-shaped deep end, calculate the main body volume using average depth, then add the hopper volume separately. The hopper is typically a small percentage of total volume.
How often should I recalculate my pool volume?
You only need to calculate once unless you make structural changes to the pool. Save the number for future chemical dosing reference.
Can I use this calculator for hot tubs and spas?
Yes. Enter the hot tub dimensions the same way. A typical 7 × 7 ft hot tub with 3 ft depth holds about 1,100 gallons.
How much does it cost to fill a pool?
Water costs vary by location, but at an average of $0.004 per gallon, filling a 20,000-gallon pool costs roughly $80 in water alone. Contact your water utility for exact rates.