You need to figure out the amount of water your swimming pool can hold in order to know the right doses of chemicals you should add. Also, when installing a heat pump, solar heater, or pool heater to your facility, you should start by knowing how much water it holds to ensure that you buy the ideal unit.

Thus, today I want to guide you on how to know the number of gallons of water in your 15’x30’ pool and other types, shapes, and sizes of pools.

## Things You Will Need

You need a ruler and a pen and paper for measuring and recording the different measurements of your pool, including the length, width, diameter, and average depth. Then we will use a fixed volume multiplier to compute the number of gallons your swimming pool holds.

## Pool Volume Formula

Length (L) x Width (W) x Average Depth (AD) x Multiplier (M) = Volume in US Gallons.

**Computing the Average Depth:**

You need to calculate the average depth of your pool if its bottom slopes by measuring the deep end and the shallow end. Add the two figures and then divided by two.

**The Multiplier:**

There are two types of multipliers that you can use:

- 5.9 for oval and round pools
- 7.5 for square, rectangle, and free-form pools

The above formula is valid for all the above-ground and inground swimming pools.

## The Actual Formula and Gallons for 15’x30’ Pool

Assume you have found:

- Length is 15’
- Width is 30’
- Average depth is 4’

Also, assume you have a **square, rectangle, or free form pool**. You can compute the number of gallons it would hold as follows:

L x W x AD x M = Volume in Gallons

15’ x 30’ x 4’ x 7.5 = 13,500 Gallons

Now assume you have an **oval pool**:

L x W X AD X M = Volume in Gallons

15’ x 30’ x 4” x 5.9 = 10,620 Gallons

You can also compute the volume of a **circular pool** as follows:

L (Diameter) x W (Diameter) X AD x M = Volume in Gallons

Standard In-ground Pool Volumes (Gallons) by Size

Pool Size in Feet | AVD in Feet 3.5 | AVD in Feet 4 | AVD in Feet 4.5 | AVD in Feet 5 |

12 x 24 | 7,600 | 8,600 | 9,700 | 10,800 |

14 x 28 | 10,300 | 11,800 | 13,200 | 14,700 |

15 x 30 | 11,800 | 13,500 | 15,200 | 16,900 |

16 x 32 | 13,400 | 15,400 | 17,300 | 19,200 |

18 x 36 | 17,000 | 19,400 | 21,900 | 24,300 |

19 x 38 | 19,000 | 21,700 | 24,400 | 27,100 |

20 x 40 | 21,000 | 24,000 | 27,000 | 30,000 |

## Final Words

It is possible to compute the volume in gallons of a 15×30 swimming pool using the formula above. One thing you should keep in mind is that you need to determine the volume of your swimming pool for various reasonsto like knowing the amount of chemicals to add and the heater to buy.

I hope my guide has given you a good idea of how you can find out the volume in your pool.