How many gallons is my pool? Calculate pool water volume for rectangular, round, oval, and kidney-shaped pools. Get gallons, fill time, and chemical estimates.
Pool Details
Pool Shape
Pool Length (ft)
Pool Width (ft)
Shallow Depth (ft)
Deep Depth (ft)
Ready to calculate
Enter your pool dimensions for volume estimates
Last updated March 2026 by our expert review team
Based on 5 ft average depth, rectangular shape.
Cherry Jane Limbago
Licensed Civil Engineer & Master Plumber
Licensed civil engineer and master plumber with 10+ years in structural design, estimation, and project management. Currently Project Engineer at Universal Robina Corporation.
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Certified Cost & Estimating Professional
AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.
See full profileUpdated March 2026
How we verify our calculatorsMeasure average depth by adding shallow end and deep end, then dividing by 2. For flat-bottom pools, just use one depth.
A standard garden hose delivers about 500 gallons per hour. A 20,000-gallon pool takes about 40 hours (nearly 2 days) to fill from empty.
Kidney and freeform pools hold about 75% of the volume of a rectangular pool with the same length, width, and depth.
Chlorine demand increases with sun exposure and swimmer load. Pools in full sun need 25 to 30% more chlorine than shaded pools.
Salt pools need 3,200 ppm of dissolved salt (about 50 lbs per 2,000 gallons). Test levels monthly with a digital salinity meter.
Use our concrete slab calculator if you are building a pool deck or patio around the pool.
Select your pool shape and enter dimensions.
Enter the shallow and deep end depths (or one depth for flat-bottom pools).
Get gallons, fill time, and chemical dosing estimates.
Formulas
Rectangular: L x W x Avg Depth x 7.48
Round: pi x r² x Avg Depth x 7.48
Oval: pi x (L/2) x (W/2) x Avg Depth x 7.48
How many gallons in a 15×30 pool?
About 12,700 gallons with 4 to 6 ft depth (5 ft average). Add 10% for uneven bottoms.
How do I measure pool depth?
Use a weighted line or pool pole at the shallow end, middle, and deep end. Average the three readings.
How long does it take to fill a pool?
At 500 gallons per hour (garden hose), a 15,000-gallon pool takes about 30 hours. Fire department tankers can do it in 2 to 3 hours but cost $200 to $500.
How much does it cost to fill a pool?
$50 to $150 for a 15,000-gallon pool using municipal water at $0.005 to $0.01 per gallon. Rates vary by city.
How much chlorine for initial fill?
2 ounces of liquid chlorine per 10,000 gallons for shock treatment. Test with a kit and adjust to 1 to 3 ppm free chlorine.
How much salt for a saltwater pool?
About 50 pounds of pool salt per 2,000 gallons to reach 3,200 ppm. A 15,000-gallon pool needs about 375 lbs.
What shape pool holds the most water?
Rectangular pools hold the most for a given footprint. Kidney and freeform shapes hold about 75% as much as the equivalent rectangle.
How do I calculate an irregular pool?
Divide the pool into simpler shapes (rectangles, circles), calculate each section, and add them together. Our calculator handles the four most common shapes.
A popular above-ground size. Uses pi x r-squared x depth. Budget $27 to $53 for water.
A compact backyard pool with a gradual slope. Needs about 1.9 oz chlorine for initial shock.
The most common residential pool size. Plan nearly 2 full days of hose time to fill from empty.
Kidney factor (0.75) reduces volume compared to a rectangle. Needs about 360 lbs of salt for a saltwater system.
Using only the deep end depth
Overestimates volume by 30 to 50%. Always average the shallow and deep end depths for an accurate calculation.
Forgetting the kidney/freeform shape factor
Kidney and freeform pools hold about 75% of the equivalent rectangle. Skipping this factor means over-dosing chemicals.
Not accounting for steps and benches
Built-in steps, benches, and sun shelves reduce actual water volume by 5 to 10%. Subtract their volume from your total.
Underestimating fill time
A garden hose delivers about 500 gallons per hour. A 20,000-gallon pool takes 40 hours, not a few hours. Plan for 2+ days.
Adding chemicals before knowing exact volume
Over-chlorination damages pool equipment and irritates skin. Always calculate volume first, then dose chemicals accordingly.
Important Disclaimer
These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.