Back to Pool & Spa CalculatorsAll Calculators

Pool & Spa Pool Volume Calculator

Author's avatar

Created by: James Porter

Last updated:

Calculate your pool's water volume in gallons, liters, cubic feet, and cubic meters for any pool shape. Essential for accurate chemical dosing, pump sizing, and equipment selection.

Pool Volume Calculator

Pool

Calculate water volume, gallons, and weight for any pool shape

Note: These results are for guidance only and shouldn't be taken as professional advice. Always double-check with a qualified expert before making decisions.

Related Calculators

Pool & Spa Calculators

Pool & Spa Calculator

Try it now

Pool & Spa Pool Chemical Dosing Calculator

Pool & Spa Calculator

Try it now

Pool & Spa Pool Chlorine Calculator

Pool & Spa Calculator

Try it now

What is a Pool Volume Calculator?

A pool volume calculator helps you determine the exact water capacity of your swimming pool in gallons, liters, cubic feet, and cubic meters. By entering your pool's shape, dimensions, and depth measurements, you can calculate the total water volume needed for chemical dosing, heating costs, and equipment sizing.

Accurate pool volume calculation is essential for proper chemical treatment, determining pump and filter requirements, and understanding operational costs. Our calculator supports all common pool shapes including rectangular, oval, kidney, circular, and L-shaped pools.

Pool Volume Calculation Formulas

Different pool shapes require specific formulas to accurately calculate water volume. All calculations use average depth for variable-depth pools.

Rectangular Pool Formula

Volume (gallons) = Length × Width × Average Depth × 7.48 Average Depth = (Shallow End + Deep End) ÷ 2

Example: 30 ft × 15 ft × 5.5 ft average depth × 7.48 = 18,513 gallons

Oval Pool Formula

Volume (gallons) = Length × Width × 3.14 ÷ 4 × Average Depth × 7.48

Example: 30 ft × 15 ft × 0.785 × 5 ft × 7.48 = 13,230 gallons

Kidney Pool Formula

Volume (gallons) = 0.45 × (Width A + Width B) × Length × Average Depth × 7.48

Example: 0.45 × (12 ft + 8 ft) × 25 ft × 5 ft × 7.48 = 8,426 gallons

Circular Pool Formula

Volume (gallons) = 3.14 × Radius² × Average Depth × 7.48 Radius = Diameter ÷ 2

Example: 3.14 × (12 ft)² × 4 ft × 7.48 = 13,500 gallons

Conversion Factors

  • 1 cubic foot = 7.48 US gallons
  • 1 gallon = 3.785 liters
  • 1 cubic meter = 264.17 gallons
  • 1 gallon of water weighs 8.34 pounds

How to Calculate Pool Volume by Shape

Measuring Your Pool

  1. Identify pool shape: Rectangular, oval, kidney, circular, or L-shaped
  2. Measure length: Longest point of the pool
  3. Measure width: Widest point perpendicular to length
  4. Measure depths: Shallow end and deep end (or single depth for uniform pools)
  5. Calculate average depth: (Shallow + Deep) ÷ 2

Rectangular Pool Example

  1. Length: 30 feet
  2. Width: 15 feet
  3. Shallow end: 3 feet
  4. Deep end: 8 feet
  5. Average depth: (3 + 8) ÷ 2 = 5.5 feet
  6. Volume: 30 × 15 × 5.5 × 7.48 = 18,513 gallons

Circular Pool Example

  1. Diameter: 24 feet
  2. Radius: 24 ÷ 2 = 12 feet
  3. Average depth: 4.5 feet
  4. Volume: 3.14 × 12² × 4.5 × 7.48 = 15,268 gallons

Kidney Pool Example

  1. Length: 28 feet
  2. Width A (widest): 14 feet
  3. Width B (narrowest): 10 feet
  4. Average depth: 5 feet
  5. Volume: 0.45 × (14 + 10) × 28 × 5 × 7.48 = 11,270 gallons

Pool Size Categories

  • Very Small: Under 10,000 gallons (plunge pools, cocktail pools)
  • Small: 10,000-15,000 gallons (compact backyard pools)
  • Medium: 15,000-25,000 gallons (standard residential pools)
  • Large: 25,000-40,000 gallons (luxury residential pools)
  • Very Large: 40,000+ gallons (estate pools, semi-commercial)

Why Calculate Pool Volume?

  • Chemical Dosing: Accurate volume ensures proper chlorine, pH adjuster, and algaecide amounts
  • Pump Sizing: Determine required pump flow rate (GPM) for proper turnover
  • Filter Selection: Match filter capacity to pool volume for effective filtration
  • Heater Sizing: Calculate BTU requirements based on water volume
  • Operating Costs: Estimate heating, chemical, and water costs accurately
  • Water Replacement: Know how much water needed to fill or refill pool
  • Salt Systems: Calculate salt pounds needed for saltwater chlorination

Pool Turnover Rate & Pump Sizing

Pool water should complete one full circulation cycle every 8-12 hours for proper filtration and chemical distribution.

Turnover Rate Formula

Pump Flow Rate (GPM) = Pool Volume (gallons) ÷ Turnover Time (hours) ÷ 60 minutes

Example Calculations

  • 15,000 gallon pool: 15,000 ÷ 8 hours ÷ 60 = 31 GPM minimum
  • 20,000 gallon pool: 20,000 ÷ 8 hours ÷ 60 = 42 GPM minimum
  • 30,000 gallon pool: 30,000 ÷ 8 hours ÷ 60 = 63 GPM minimum

Pump Sizing Guidelines

  • Small pools (under 15,000 gal): 1-1.5 HP pump, 40-60 GPM
  • Medium pools (15,000-25,000 gal): 1.5-2 HP pump, 50-75 GPM
  • Large pools (25,000-40,000 gal): 2-3 HP pump, 75-100 GPM
  • Very large pools (40,000+ gal): 3+ HP pump, 100+ GPM

Chemical Dosing Based on Volume

Pool chemical dosing accuracy depends on knowing exact water volume. Incorrect volume estimates lead to water balance issues.

Common Chemical Dosing Rates

  • Chlorine shock: 1 pound per 10,000 gallons (raises chlorine ~10 ppm)
  • pH increaser (soda ash): 6 oz per 10,000 gallons (raises pH by 0.2)
  • pH decreaser (sodium bisulfate): 8 oz per 10,000 gallons (lowers pH by 0.2)
  • Alkalinity increaser: 1.5 lbs per 10,000 gallons (raises alkalinity ~10 ppm)
  • Calcium hardness: 10 oz per 10,000 gallons (raises hardness ~10 ppm)
  • Algaecide: Follow manufacturer instructions based on gallons

Saltwater Pool Calculations

Saltwater pools require 3,000-3,500 ppm salt concentration (parts per million).

Salt Needed (lbs) = Pool Volume (gallons) × 0.025

Example: 20,000 gallon pool × 0.025 = 500 pounds of salt for initial fill

Frequently Asked Questions

How do I calculate pool volume in gallons?

Calculate pool volume by multiplying length × width × average depth × 7.48 for rectangular pools. For other shapes, use shape-specific formulas. Average depth is (shallow end + deep end) ÷ 2. The 7.48 factor converts cubic feet to gallons.

How many gallons is a 15x30 pool?

A 15x30 foot pool with an average depth of 5 feet contains approximately 16,830 gallons (15 × 30 × 5 × 7.48). The exact volume depends on the pool's depth profile - deeper pools contain more water.

What is the average pool size in gallons?

The average residential pool contains 15,000-25,000 gallons. Small pools are 10,000-15,000 gallons, medium pools 15,000-25,000 gallons, and large pools 25,000-40,000 gallons. Above-ground pools typically hold 10,000-15,000 gallons.

Why is knowing pool volume important?

Accurate pool volume is essential for proper chemical dosing, pump sizing, filter selection, heater BTU requirements, and operating cost estimates. Incorrect volume calculations lead to improper water chemistry and potential equipment issues.

How much does pool water weigh?

Water weighs 8.34 pounds per gallon. A 20,000 gallon pool contains 166,800 pounds of water (about 83.4 tons). This weight is important for structural considerations, deck support, and understanding the mass your pool equipment must circulate.

What is pool turnover rate?

Turnover rate is the time required to circulate the entire pool volume through the filter once. Pools should turn over every 8-12 hours. Calculate required pump flow rate by dividing pool gallons by turnover hours, then dividing by 60 for GPM.

How do you measure an irregularly shaped pool?

For irregular pools, divide the pool into regular shapes (rectangles, circles), calculate each section's volume separately, and add them together. For kidney or L-shaped pools, use approximation formulas that account for the curved or complex geometry.

Sources and References

  1. Pool & Hot Tub Alliance. (2024). Pool Volume Calculation Standards and Best Practices.
  2. Association of Pool & Spa Professionals. (2024). Chemical Dosing Guidelines Based on Pool Volume.
  3. Centers for Disease Control and Prevention. (2024). Healthy Swimming Pool Water Chemistry Guidelines.
  4. National Swimming Pool Foundation. (2024). Pool Operator Handbook - Volume and Chemical Calculations.