Pool Gallon Calculator

Introduction (~110 words):

Your pool holds tens of thousands of gallons of water  but do you know the exact number? Whether you're adding chlorine, shocking the water, or calculating your water bill, the gallon count of your pool determines everything. Get it wrong by even 20%, and your chemical treatments won't work properly.

This free pool gallon calculator gives you an instant, accurate result for any pool shape rectangular, round, oval, or kidney. Just enter your pool's dimensions and depth, and you'll have your answer in seconds. Below the calculator, you'll also find the exact formulas, worked examples, and a quick-reference size chart.

H2: What is a Pool Gallon Calculator?

A pool gallon calculator is a digital tool that estimates the total volume of water your swimming pool holds, expressed in US gallons. It uses your pool's length, width (or diameter), and depth to run a standard volume formula — then converts the result from cubic feet into gallons using the constant 7.48 gallons per cubic foot.

Pool owners use this number for three main reasons: calculating the correct dose of pool chemicals, estimating the cost of filling or refilling the pool, and sizing pool equipment like pumps and filters correctly. According to the APSP (Association of Pool and Spa Professionals), over 5.7 million residential pools exist in the United States as of 2024  and accurate water volume is the foundation of every maintenance task in every one of them.

H3: Why Knowing Your Pool's Gallon Count Matters

Chemical manufacturers  including major brands like Hayward and Pentair  base every treatment dosage on pool volume in gallons. Shock treatments, algaecide, pH adjusters, and chlorine tablets all require you to know this number first. Using the wrong volume means under-treating (algae blooms) or over-treating (skin and eye irritation).

Beyond chemicals, your pool's gallon count also determines pump sizing. The NSPF recommends that a pool pump turn over the entire water volume at least once every 8 hours. A pool with 20,000 gallons needs a significantly different pump than one with 10,000 gallons.

H3: What Information You'll Need Before You Calculate

You'll need three measurements: your pool's length and width (or diameter for round pools), and your pool's depth at both the shallow and deep end. You do not need to drain the pool to measure  use a tape measure dropped vertically into the water from the pool deck.

H2: The Pool Volume Formula  How Gallons Are Calculated

The pool gallon formula is a two-step process: first calculate volume in cubic feet, then multiply by 7.48 to convert to gallons. The shape of your pool determines which formula you use in step one.

Featured Snippet Block (targets: "What is the formula for pool volume?" and "How do I calculate gallons in my pool?"):

To calculate pool gallons, multiply your pool's length by width by average depth to get cubic feet, then multiply by 7.48 (gallons per cubic foot). For a round pool, use 3.14 × radius² × average depth × 7.48. Average depth equals shallow end depth plus deep end depth, divided by 2.

H3: Rectangular Pool Formula

Rectangular and square pools use the simplest formula:

Gallons = Length (ft) × Width (ft) × Average Depth (ft) × 7.48

Example: A pool that is 15 ft × 30 ft with an average depth of 5 ft contains: 15 × 30 × 5 × 7.48 = 16,830 gallons

H3: Circular Pool Formula

For round and circular pools, replace length × width with the area of a circle:

Gallons = 3.14 × Radius² × Average Depth (ft) × 7.48

The radius is half the diameter. For a 24-foot round pool: radius = 12 ft 3.14 × 144 × 4 × 7.48 = 13,527 gallons

H3: Oval Pool Formula

Oval pools use a combined approach  treating the oval as an elongated circle:

Gallons = 3.14 × (Long Diameter ÷ 2) × (Short Diameter ÷ 2) × Average Depth × 7.48

Example: A 16 × 32 ft oval pool with 5 ft average depth: 3.14 × 16 × 8 × 5 × 7.48 = 15,041 gallons

H3: How to Calculate Average Pool Depth

Most pools have a shallow end and a deep end, so you can't use a single depth measurement. Average depth is calculated as:

Average Depth = (Shallow End Depth + Deep End Depth) ÷ 2

For a pool with a 3-foot shallow end and a 6-foot deep end: (3 + 6) ÷ 2 = 4.5 feet average depth

If your pool has a gradual slope rather than a defined deep end, measure depth at four equally spaced points and average those four readings.

H2: How to Use This Pool Gallon Calculator

H3: Step-by-step walkthrough of inputs

1. Select your pool's shape from the dropdown (rectangular, round, oval, kidney/irregular)
2. Enter your pool's length and width in feet  or diameter if round
3. Enter your shallow end depth in feet
4. Enter your deep end depth in feet (the calculator averages these automatically)
5. Click "Calculate Gallons"

H3: How to read and interpret your results

The calculator displays three outputs: total US gallons, total cubic feet, and total liters. Use the gallon figure for all US-standard chemical treatments. The cubic feet figure is useful when sizing filters and pumps. The liter figure is helpful if your chemical packaging uses metric measurements.

H2: Real-World Examples  Pool Gallon Counts by Size

H3: Example 1: 15 × 30 ft Rectangular Inground Pool This is one of the most common residential inground pool sizes in the US. With a shallow end of 3 ft and deep end of 6 ft: Average depth = 4.5 ft 15 × 30 × 4.5 × 7.48 = 15,147 gallons

H3: Example 2 :  24 ft Round Above Ground Pool The Intex 24-foot round pool is one of the best-selling above ground pool sizes. With a uniform depth of 4 ft: 3.14 × 12² × 4 × 7.48 = 13,527 gallons

H3: Example 3: 16 × 32 ft Oval Pool Common in mid-sized backyards. With a 3.5 ft shallow end and 5 ft deep end (avg 4.25 ft): 3.14 × 16 × 8 × 4.25 × 7.48 = 12,775 gallons

H2: Pool Gallons by Shape  Quick Reference Chart

H2: Why Your Pool's Gallon Count Affects Chemical Dosing

Every chemical treatment is dosed per 10,000 gallons. A 20,000-gallon pool needs exactly twice the chemical of a 10,000-gallon pool. Even a 15% error in your gallon calculation — which is common when people use a single depth reading instead of average depth — can result in under-chlorinated water that fails to meet EPA recreational water safety guidelines. Always use average depth for the most accurate dosing baseline.

H2: Common Mistakes When Calculating Pool Volume

H3: Using maximum depth instead of average depth

The single most common error is measuring only at the deepest point of the pool. This inflates your gallon count by 20–35% and causes you to over-dose every chemical treatment. Always calculate average depth using the shallow and deep end measurements.

H3: Measuring diameter instead of radius for round pools

For the circular formula, you need the radius  which is half the diameter. A 24-foot pool has a radius of 12 feet. Using 24 instead of 12 in the formula produces a result 4× too large. The calculator on this page handles this conversion automatically if you enter diameter.

Conclusion  Use Your Gallon Count to Maintain a Healthier Pool

Knowing exactly how many gallons your pool holds is the starting point for every maintenance task  from chlorine dosing to pump sizing to water costs. The formula is simple: volume in cubic feet × 7.48 = total gallons. Use the calculator above for an instant, accurate answer.

Introduction (~110 words):

Your pool holds tens of thousands of gallons of water  but do you know the exact number? Whether you're adding chlorine, shocking the water, or calculating your water bill, the gallon count of your pool determines everything. Get it wrong by even 20%, and your chemical treatments won't work properly.

This free pool gallon calculator gives you an instant, accurate result for any pool shape rectangular, round, oval, or kidney. Just enter your pool's dimensions and depth, and you'll have your answer in seconds. Below the calculator, you'll also find the exact formulas, worked examples, and a quick-reference size chart.

H2: What is a Pool Gallon Calculator?

A pool gallon calculator is a digital tool that estimates the total volume of water your swimming pool holds, expressed in US gallons. It uses your pool's length, width (or diameter), and depth to run a standard volume formula — then converts the result from cubic feet into gallons using the constant 7.48 gallons per cubic foot.

Pool owners use this number for three main reasons: calculating the correct dose of pool chemicals, estimating the cost of filling or refilling the pool, and sizing pool equipment like pumps and filters correctly. According to the APSP (Association of Pool and Spa Professionals), over 5.7 million residential pools exist in the United States as of 2024  and accurate water volume is the foundation of every maintenance task in every one of them.

H3: Why Knowing Your Pool's Gallon Count Matters

Chemical manufacturers  including major brands like Hayward and Pentair  base every treatment dosage on pool volume in gallons. Shock treatments, algaecide, pH adjusters, and chlorine tablets all require you to know this number first. Using the wrong volume means under-treating (algae blooms) or over-treating (skin and eye irritation).

Beyond chemicals, your pool's gallon count also determines pump sizing. The NSPF recommends that a pool pump turn over the entire water volume at least once every 8 hours. A pool with 20,000 gallons needs a significantly different pump than one with 10,000 gallons.

H3: What Information You'll Need Before You Calculate

You'll need three measurements: your pool's length and width (or diameter for round pools), and your pool's depth at both the shallow and deep end. You do not need to drain the pool to measure  use a tape measure dropped vertically into the water from the pool deck.

H2: The Pool Volume Formula  How Gallons Are Calculated

The pool gallon formula is a two-step process: first calculate volume in cubic feet, then multiply by 7.48 to convert to gallons. The shape of your pool determines which formula you use in step one.

Featured Snippet Block (targets: "What is the formula for pool volume?" and "How do I calculate gallons in my pool?"):

To calculate pool gallons, multiply your pool's length by width by average depth to get cubic feet, then multiply by 7.48 (gallons per cubic foot). For a round pool, use 3.14 × radius² × average depth × 7.48. Average depth equals shallow end depth plus deep end depth, divided by 2.

H3: Rectangular Pool Formula

Rectangular and square pools use the simplest formula:

Gallons = Length (ft) × Width (ft) × Average Depth (ft) × 7.48

Example: A pool that is 15 ft × 30 ft with an average depth of 5 ft contains: 15 × 30 × 5 × 7.48 = 16,830 gallons

H3: Circular Pool Formula

For round and circular pools, replace length × width with the area of a circle:

Gallons = 3.14 × Radius² × Average Depth (ft) × 7.48

The radius is half the diameter. For a 24-foot round pool: radius = 12 ft 3.14 × 144 × 4 × 7.48 = 13,527 gallons

H3: Oval Pool Formula

Oval pools use a combined approach  treating the oval as an elongated circle:

Gallons = 3.14 × (Long Diameter ÷ 2) × (Short Diameter ÷ 2) × Average Depth × 7.48

Example: A 16 × 32 ft oval pool with 5 ft average depth: 3.14 × 16 × 8 × 5 × 7.48 = 15,041 gallons

H3: How to Calculate Average Pool Depth

Most pools have a shallow end and a deep end, so you can't use a single depth measurement. Average depth is calculated as:

Average Depth = (Shallow End Depth + Deep End Depth) ÷ 2

For a pool with a 3-foot shallow end and a 6-foot deep end: (3 + 6) ÷ 2 = 4.5 feet average depth

If your pool has a gradual slope rather than a defined deep end, measure depth at four equally spaced points and average those four readings.

H2: How to Use This Pool Gallon Calculator

H3: Step-by-step walkthrough of inputs

1. Select your pool's shape from the dropdown (rectangular, round, oval, kidney/irregular)
2. Enter your pool's length and width in feet  or diameter if round
3. Enter your shallow end depth in feet
4. Enter your deep end depth in feet (the calculator averages these automatically)
5. Click "Calculate Gallons"

H3: How to read and interpret your results

The calculator displays three outputs: total US gallons, total cubic feet, and total liters. Use the gallon figure for all US-standard chemical treatments. The cubic feet figure is useful when sizing filters and pumps. The liter figure is helpful if your chemical packaging uses metric measurements.

H2: Real-World Examples  Pool Gallon Counts by Size

H3: Example 1: 15 × 30 ft Rectangular Inground Pool This is one of the most common residential inground pool sizes in the US. With a shallow end of 3 ft and deep end of 6 ft: Average depth = 4.5 ft 15 × 30 × 4.5 × 7.48 = 15,147 gallons

H3: Example 2 :  24 ft Round Above Ground Pool The Intex 24-foot round pool is one of the best-selling above ground pool sizes. With a uniform depth of 4 ft: 3.14 × 12² × 4 × 7.48 = 13,527 gallons

H3: Example 3: 16 × 32 ft Oval Pool Common in mid-sized backyards. With a 3.5 ft shallow end and 5 ft deep end (avg 4.25 ft): 3.14 × 16 × 8 × 4.25 × 7.48 = 12,775 gallons

H2: Pool Gallons by Shape  Quick Reference Chart

H2: Why Your Pool's Gallon Count Affects Chemical Dosing

Every chemical treatment is dosed per 10,000 gallons. A 20,000-gallon pool needs exactly twice the chemical of a 10,000-gallon pool. Even a 15% error in your gallon calculation — which is common when people use a single depth reading instead of average depth — can result in under-chlorinated water that fails to meet EPA recreational water safety guidelines. Always use average depth for the most accurate dosing baseline.

H2: Common Mistakes When Calculating Pool Volume

H3: Using maximum depth instead of average depth

The single most common error is measuring only at the deepest point of the pool. This inflates your gallon count by 20–35% and causes you to over-dose every chemical treatment. Always calculate average depth using the shallow and deep end measurements.

H3: Measuring diameter instead of radius for round pools

For the circular formula, you need the radius  which is half the diameter. A 24-foot pool has a radius of 12 feet. Using 24 instead of 12 in the formula produces a result 4× too large. The calculator on this page handles this conversion automatically if you enter diameter.

Conclusion  Use Your Gallon Count to Maintain a Healthier Pool

Knowing exactly how many gallons your pool holds is the starting point for every maintenance task  from chlorine dosing to pump sizing to water costs. The formula is simple: volume in cubic feet × 7.48 = total gallons. Use the calculator above for an instant, accurate answer.