An 18x36 Pool Holds Approximately 13,500 Gallons

An 18-foot by 36-foot swimming pool, assuming a standard average depth of 4 feet, contains an estimated 13,500 gallons of water. This calculation provides a general guideline for pool volume. For precise volume, the exact average depth of your pool is essential. Understanding this volume is useful for water treatment and maintenance.

Calculating Pool Volume

To determine the water capacity of your pool, you need to know its dimensions and average depth. The most common method involves converting all measurements to feet and then multiplying length by width by average depth. This gives you the volume in cubic feet.

Converting Cubic Feet to Gallons

Once you have the volume in cubic feet, you can convert it to gallons. The conversion factor is approximately 7.48 gallons per cubic foot.

Formula: Volume (cubic feet) x 7.48 = Volume (gallons)

Example Calculation for an 18x36 Pool

Let's apply the formula to your pool dimensions.
  • Pool Length: 36 feet
  • Pool Width: 18 feet
  • Average Depth: 4 feet (assumed)

Volume in cubic feet = 36 ft x 18 ft x 4 ft = 2,592 cubic feet

Volume in gallons = 2,592 cubic feet x 7.48 gallons/cubic foot = 19,388.16 gallons

Note: This example uses an assumed average depth of 4 feet. If your pool has a different average depth, adjust the calculation accordingly. A sloped pool will have a different average depth than a constant depth pool.

Pool Volume Considerations

The actual volume can vary based on pool shape and whether it has a constant depth or a sloped bottom. For shallower pools, the gallon count will be lower, and for deeper pools, it will be higher.

Water Volume and Maintenance

Knowing your pool's gallon capacity is crucial for:
  • Chemical Dosing: Ensuring the correct amount of chemicals are added for water balance and sanitation.
  • Filtration: Understanding how long your filter needs to run to circulate the entire volume of water.
  • Water Replenishment: Calculating how much water is needed to refill after evaporation or cleaning.

Comparison of Gallon Estimates by Depth

| Pool Dimensions | Average Depth (feet) | Estimated Volume (gallons) | | :-------------- | :------------------- | :------------------------- | | 18x36 | 3 | 11,600 | | 18x36 | 4 | 15,500 | | 18x36 | 5 | 19,300 |