A pool volume calculator determines exactly how many gallons of water your swimming pool holds based on its shape and dimensions. Knowing your pool's volume is the foundation for accurate chemical dosing, fill time estimates, and water weight calculations. Enter your pool shape, dimensions, and depths below for instant results.
Pool Dimensions
Garden hose ≈ 9–17 GPM · 1.5-inch line ≈ 30–40 GPM
Pool Volume Formulas by Shape
| Shape | Formula | Multiplier |
|---|---|---|
| Rectangular | L × W × Avg Depth × 7.48 | 7.48 |
| Circular | π × r² × Avg Depth × 7.48 | 7.48 |
| Oval | L × W × Avg Depth × 5.9 | 5.9 |
| Kidney / Freeform | L × W × Avg Depth × 6.7 | 6.7 |
Multipliers convert cubic feet to US gallons adjusted for each shape's footprint relative to its bounding rectangle.
How to Use the Pool Volume Calculator
Knowing your pool's exact volume in gallons is the single most important number for pool ownership. Every chemical dosage, every fill time estimate, and every water weight calculation depends on it. This pool volume calculator handles rectangular, circular, oval, and kidney-shaped pools using the industry-standard formulas, so you get an accurate number regardless of your pool's shape.
Step 1: Select Your Pool Shape
Choose from the four shape options: Rectangular, Circular, Oval, or Kidney/Freeform. Each shape uses a different geometric formula. Rectangular pools use the full L × W area; circular pools use π × r²; oval pools account for the reduced area compared to a rectangle; and kidney/freeform pools use an average multiplier that approximates typical irregular inground designs.
Step 2: Enter Your Pool's Dimensions
For rectangular, oval, and kidney pools, enter the length and width in feet measured at the waterline. For circular pools, enter the diameter. If your pool tapers or has a cove, measure across the widest points. You can convert inches to feet by dividing by 12 — for example, a 15 ft 6 in width is 15.5 ft.
Step 3: Enter Shallow and Deep End Depths
The pool volume calculator uses the average depth, which is the midpoint between your shallow and deep end measurements. Enter both depths separately and the calculator averages them automatically: (shallow depth + deep depth) ÷ 2. For flat-bottom pools like above-ground pools, enter the same value for both. Measure depth from the waterline to the pool floor, not the total wall height.
Step 4: Enter Your Fill Flow Rate
To get an accurate fill time estimate, enter your water source's flow rate in gallons per minute (GPM). A standard 5/8-inch garden hose delivers roughly 9–17 GPM depending on your water pressure. A 3/4-inch hose runs at 13–23 GPM. If you're using a dedicated 1.5-inch fill line from your utility, flow rates of 30–50 GPM are common. If you are unsure, time how long it takes to fill a 5-gallon bucket and divide: 5 ÷ seconds × 60 = GPM.
Step 5: Review Your Results
Click "Calculate Pool Volume" to see your pool's volume in both US gallons and liters, total water weight in pounds, estimated fill time, and a quick chemical dosing reference table showing how much chlorine, shock, and other chemicals you'd need per 10,000 gallons scaled to your pool size. For precise chemical treatment based on your current water test readings, use the companion Pool Chemical Calculator.
Tips for Accurate Measurements
Measure your pool at the waterline, not at the deck or coping edge. For kidney and freeform pools, measure the longest length and widest width across the entire pool — the kidney multiplier (6.7) already accounts for the concave side. If your pool has a beach entry or tanning ledge, exclude those areas from the main volume calculation and add them separately. A 10% buffer above the calculated volume is wise when ordering water treatment chemicals for the first fill.
FAQ
Is this pool volume calculator free to use?
Yes, this pool volume calculator is completely free with no signup required and no limits. Every calculation runs locally in your browser — your pool dimensions are never sent to any server. Use it as often as you need.
Is my data private when I use this tool?
Absolutely. All calculations are performed client-side using JavaScript in your browser. No pool dimensions, locations, or personal information are ever transmitted or stored. Your data stays entirely on your device.
How many gallons does a typical swimming pool hold?
A standard residential inground pool (30 ft × 15 ft, 3.5 ft shallow to 8 ft deep) holds roughly 17,000–20,000 gallons. Above-ground pools typically hold 5,000–15,000 gallons. Small plunge pools can be as little as 2,000 gallons, while large custom pools can exceed 50,000 gallons.
Why does pool shape change the volume multiplier?
Different shapes use different geometric formulas. Rectangular pools use L × W × depth × 7.48 (exact cubic feet to gallons). Circular pools use π × r² × depth × 7.48. Oval pools approximate with L × W × depth × 5.9 (accounting for the reduced area vs. a rectangle). Kidney/freeform pools use L × W × depth × 6.7, which averages typical irregular shapes.
What is average depth and how do I calculate it?
Average depth is the midpoint between your shallow end and deep end depths. For example, if your pool is 3 ft at the shallow end and 8 ft at the deep end, the average depth is (3 + 8) ÷ 2 = 5.5 ft. This calculator does the averaging automatically — just enter both depths separately.
How long will it take to fill my pool with a garden hose?
A standard garden hose delivers about 9–17 gallons per minute (GPM) depending on water pressure. At 10 GPM, filling a 20,000-gallon pool takes roughly 33 hours. Enter your flow rate in the calculator to get a personalized fill time estimate. Most homeowners use a 1.5–2 inch supply line at 20–40 GPM for faster fills.
How much does it cost to fill a pool with water?
Water costs approximately $0.001–$0.005 per gallon depending on your municipality. A 20,000-gallon pool costs roughly $20–$100 to fill from a municipal water supply. Sewer fees may also apply if your utility charges based on water in. Contact your water utility to check if they offer a pool fill rate exemption for sewer charges.
How much chlorine does my pool need based on volume?
As a general rule, shock treatment requires 1 lb of calcium hypochlorite (65% strength) per 10,000 gallons to raise free chlorine by about 5 ppm. For routine maintenance chlorine, 1 oz of trichlor tablet per 10,000 gallons per day is typical. The calculator shows a chlorine dosing reference in the results.