poolchemistrycalc

18 × 33 ft oval pool volume

An 18 × 33 ft oval pool holds

13,400gal 50,700L

Measured at the water, not at the wall: a 52 in wall less 6 in of freeboard leaves 46 in of water.

Section through an 18 × 33 ft oval pool: a 52 in wall with 46 in of water standing 6 in below its top, and the 13,400 gal figure computed from the water. 18 ft × 33 ft 52 in wall not the depth used 6 in of freeboard 46 in of water gallons use this

Gallons at every fill

Wall height is what the box says; the water stops 6 in below it, and the gallons are worked from the water.
Wall Water Holds
48 in 42 in 12,200 gal
46,200 L
52 in 46 in
this page		 13,400 gal
50,700 L
54 in 48 in 14,000 gal
53,000 L
At 13,400 gal

What to add

One product for each adjustment, worked at this page's own gallons. Follow a quantity to set your own reading.
Fixes Product Add
Lower pH
−0.5 pH 		HASA Dry Acid 1.68 lb
Raise total alkalinity
+40 ppm 		HASA Alkalinity Up 7.50 lb
Raise pH
+0.3 pH 		HASA Soda Ash 4.02 lb
Raise free chlorine
+2.5 ppm 		HASA CHLOR 1.07 qt
Shock the pool
+9.5 ppm 		HASA CHLOR 4.07 qt

Not quite your pool?

feet, the long side
feet
inches, the figure on the box
The gap between the water and the top rail, usually 4 to 6 inches

Change any measurement and every figure on this page is worked again: the gallons, the drawing, the fill table and each dose.

An oval is worked here as an ellipse. If yours has straight sides and round ends, it holds more: 15,000 gallons (56,800 litres) at the same depth.

Pools near this one

Updated October 2026

Sources and dates

Ranges are quoted from the code named beside them, product strengths from the manufacturer's own product page, each retrieved on the date shown.

This site publishes calculated water volumes and chemical quantities for home pool and spa owners. It is not a health, safety or professional service, and it does not replace the instructions printed on the product you are holding. Not affiliated with, endorsed by or sponsored by HASA, Pyrock Chemical, Pentair, Hayward, Sonoma Hot Tubs, the Centers for Disease Control and Prevention, or any state health department. Product names are the trademarks of their owners and appear here only to identify the strength of what is in the container.