Last updated: March 2026
What Is the Pool Volume Calculator?
The Pool Volume Calculator tells you exactly how many gallons of water your swimming pool holds. With over 10.7 million residential pools in the United States, knowing your pool volume is the single most important number for proper maintenance. Every chemical you add, from chlorine to pH adjuster to algaecide, is dosed based on your pool's gallon count. Get it wrong and you risk cloudy water, algae blooms, or skin and eye irritation.
This calculator supports four common pool shapes: rectangular, circular, oval, and L-shaped. It handles both constant-depth and variable-depth pools, converting your measurements into gallons, liters, and cubic feet instantly. Beyond volume, it estimates fill time with one or two garden hoses, water cost, a complete chemical dosing guide for initial fills, and ongoing weekly maintenance amounts.
How to Calculate Pool Volume
Step 1: Choose your pool shape. Select rectangular for standard in-ground or above-ground pools, circular for round above-ground pools, oval for elongated curved pools, or L-shaped for pools with two distinct rectangular sections. The calculator adjusts the formula automatically.
Step 2: Enter dimensions. Measure your pool at the waterline in feet and inches. For length and width, measure the longest and widest points. For circular pools, measure the diameter across the center. Accuracy here directly affects the reliability of your chemical dosing calculations.
Step 3: Set the depth. If your pool has a uniform depth, use constant depth mode. For pools with a shallow end and deep end, switch to variable depth mode and enter both. The calculator averages them to determine the effective volume. Most residential pools range from 3.5 feet on the shallow end to 8 feet at the deep end.
Step 4: Review results. The calculator instantly displays your pool volume in gallons (the primary unit used for chemical dosing in the US), liters, and cubic feet. Below the volume, you will find fill time estimates, a complete chemical dosing table for initial fills, and weekly maintenance amounts to keep your pool crystal clear all season.
Key Features
The calculator supports four pool shapes with visual icons so you can quickly identify and select the right geometry. Variable depth mode lets you enter separate shallow and deep end measurements, which the tool averages for a far more accurate result than guessing a single depth value. All inputs accept both feet and inches for precision without needing to convert fractions.
The chemical dosing guide covers seven essential pool chemicals, scaled precisely to your pool's volume. Rather than looking up dosing charts for each chemical individually, you get a single reference table with all the amounts you need. The weekly maintenance section helps you budget for ongoing chemical costs and plan your chlorine purchases for the season.
Hot tub mode provides quick presets for common spa sizes of 300, 400, and 500 gallons, or lets you enter a custom volume. Since hot tub chemicals are dosed identically to pool chemicals but in much smaller amounts, this mode gives you properly scaled dosing amounts without needing to measure physical dimensions.
Frequently Asked Questions
How do I calculate how many gallons are in my pool?
Multiply the pool's length, width, and average depth in feet, then multiply by 7.48 to convert cubic feet to gallons. For a 30 by 15 foot pool with an average depth of 5 feet, that is 30 times 15 times 5 times 7.48, which equals 16,830 gallons. Circular and oval pools use a similar approach but substitute the area formula for a circle or ellipse.
How long does it take to fill a pool with a garden hose?
A standard garden hose delivers about 480 gallons per hour (8 gallons per minute). A typical 15,000-gallon pool takes about 31 hours to fill with one hose, or roughly 16 hours with two hoses running simultaneously. Flow rate varies by water pressure and hose diameter, so your actual time may differ.
Why do I need to know my pool volume?
Pool volume is essential for proper chemical dosing. Chlorine, pH adjusters, algaecide, and every other pool chemical is dosed based on gallons of water. Adding too much can irritate skin and damage equipment, while too little leaves the water unsafe. You also need volume to estimate fill time and water cost.
What is the average depth of a pool with a shallow and deep end?
Add the shallow end depth and the deep end depth together, then divide by two. For example, a pool with a 3.5-foot shallow end and an 8-foot deep end has an average depth of 5.75 feet. This averaging method works well for pools with a gradual slope from shallow to deep.
How much does it cost to fill a pool with water?
The average US water rate is about $0.004 per gallon, so filling a 20,000-gallon pool costs roughly $80 in water. Rates vary significantly by municipality, from as low as $0.002 to over $0.008 per gallon. Check your local water utility rate schedule or a recent bill for the most accurate estimate.