The Math Formula Is:

Length X Width X Average Depth X Multiplier = Gallons

Use The Following Multiplier:

Rectangle, square pools: Use multiplier = 7.5   

Round or Oval pool: Use multiplier = 5.9

Example: 18' round pool 54” walls (pool is filled to within 6” of the top of the pool)

18' x 18' x 4' x 5.9 = 7,646 Gallons

What Size Pump Do I Need For My Pool?

Keep in mind that a 1.5” diameter hose has a maximum flow rate of 42  GPM.
Determine the gallons per minute (GPM) flow rate your pool needs. A good turn over time for residential pools is 8 to 10 hours (move all the water in the pool every 8 to 10 hours).

Pool size in gallons,

Divided by the desired turner over time (in this case eight hours)

Divided by 60 minutes,

Equals Flow rate in GPM

Pool Size	Gallons	8 hour flow rate	Pump Size
12 ft Round	3,398 gallons	8 GPM	½ hp
15 ft Round	5,310 gallons	11 GPM	½ hp
18 ft Round	7,646 gallons	16 GPM	¾ hp
21 ft Round	10,408 gallons	22 GPM	¾ hp
24 ft Round	13,594 gallons	28 GPM	1 hp
27 ft Round	17,205 gallons	36 GPM	1 hp
30 ft Round	21,240 gallons	44 GPM	1.5 hp
33 ft Round	25,700 gallons	54 GPM	1.5 hp
12' x 24' Oval	6,797 gallons	14 GPM	¾ hp
15' x 30' Oval	10,620 gallons	22 GPM	¾ hp
16' x 32' Oval	12,084 gallons	25 GPM	1.5 hp
18' x 33' Oval	14,019 gallons	29 GPM	1.5 hp

About the author: Mr. Glasgow has been a merchant for forty five years. Having managed and or owned discount stores and specialty retail stores. Mr. Glasgow currently owns and operates Patiostore.com a specialty retailer of patio furniture and other related back yard products.