How many gallons is an 18x33 oval pool?
An 18 × 33 ft above-ground oval pool with a 52 in wall holds roughly 14,200 gallons.
On this page (7 sections)
By geometry at 90% fill, it holds about 15,300 gallons with a 52 in wall (14,100 at 48 in, 15,900 at 54 in). Real frame and steel-wall pools usually hold about 7% less.
Quick answer for an 18x33
Whether you call it 18 × 33 or 33 × 18, it's the same pool: 33 ft end to end, 18 ft across. The data block gives geometry and the frame estimate for 48, 52, and 54 in walls. Going from a 48 to a 54 in wall adds about 1,765 gallons, as much water as a small 12 ft round pool.
| Wall height | Geometry (straight sides, round ends) | Frame pool estimate (× 0.93) |
|---|---|---|
| 48 in wall | 14,124 gal53,465 L | 13,135 gal |
| 52 in wall | 15,301 gal57,920 L | 14,230 gal |
| 54 in wall | 15,889 gal60,148 L | 14,777 gal |
Oval above-ground pools are a rectangle with two half-circle ends. A true ellipse holds less.
| Change | Amount |
|---|---|
| +1 ppm FC (12.5% liquid chlorine) | 15 fl oz431 mL |
| +10 ppm TA (baking soda) | 2.0 lb904 g |
| +10 ppm CYA (stabilizer) | 1.2 lb539 g |
Closest full chart: 15,000 gal dose chart.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
Above-ground oval vs inground rectangle
An above-ground oval has two straight sides joined by half circles. For 18 × 33 ft, the straight middle section is 15 ft long (33 − 18) and 18 ft wide: 270 square feet. The two half circles together make one 18 ft circle: about 254 square feet. Total: about 524 square feet. A rectangle of the same outer size would cover 594 square feet and hold 13% more water at the same depth.
| Pool | Depth | Gallons |
|---|---|---|
| Above-ground oval, round ends | 52 in wall, 90% fill | 15,301 gal (estimate 14,230) |
| True ellipse | 52 in wall, 90% fill | 13,610 gal |
| Inground rectangle, flat | 4 ft | 17,774 gal |
| Inground rectangle, sloped | 3.5 to 6 ft | 21,106 gal |
| Inground rectangle, sloped | 3.5 to 8 ft | 25,550 gal |
Measure an oval inside the wall: across the straight sides for the width, end to end through the middle for the length.
No 18 × 33 oval has a manufacturer capacity in our database yet. If your manual gives one, use it in every calculator on this site.
Starting doses for this volume
For the 52 in frame estimate of 14,230 gallons:
- Chlorine, +1 ppm: 15 fl oz of 12.5% liquid chlorine, 18 fl oz of 10%, or 29 fl oz of 6% bleach.
- Alkalinity, +10 ppm: 2.0 lb of baking soda.
- Stabilizer (CYA) on a fresh fill: 3.55 lb for CYA 0 to 30 ppm; 4.75 lb to 40 ppm.
- Salt for a new salt system: about 380 lb to reach 3,200 ppm (nine 40 lb bags plus 20 lb).
With a 54 in wall (14,777 gallons), chlorine is still about 15 fl oz of 12.5% per ppm, and stabilizer to 30 ppm is 3.7 lb. Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling. For shock and acid amounts, see the 15,000-gallon dose chart.
Calculator: your exact depth
Set the length to 33 ft and the width to 18 ft, pick "Straight sides, round ends", then enter your wall height and fill level.
Fill time and water cost
At about 14,200 gallons, filling takes about 47 hours at 5 gallons per minute or 24 hours at 10. If your water supply allows, run two hoses from separate spigots to cut the time. The water costs about $14.23 for each $1 per 1,000 gallons on your water bill. Enter your own rate in the fill cost calculator. The finished pool holds roughly 118,700 lb of water (14,230 gallons × 8.34 lb), so the whole oval footprint must be level and firm before you fill.
Safety. Add one chemical at a time with the pump on, and wait at least 30 minutes between chlorine and acid. Keep lids closed, and store chlorine and acid in separate places. Poison Control: 1-800-222-1222.
FAQ
How many gallons in a 33x18 oval pool?
About 14,124 gallons with a 48 in wall, 15,301 with 52 in, and 15,889 with 54 in, by geometry at 90% fill. Frame pools usually hold about 7% less: 13,135, 14,230, and 14,777 gallons.
How much chlorine for an 18x33 pool?
About 15 fl oz of 12.5% liquid chlorine or 29 fl oz of 6% bleach per 1 ppm. A 3 ppm top-up is about 44 fl oz of 12.5% chlorine.
Sources
- Weight of water, 8.34 lb per gallon: USGS Water Science School
- Hayward, salt dosing: hayward.com
- Oval formula, correction factors, and dose math: methodology