How many gallons is an 18 ft round pool?
An 18 ft round pool holds about 5,500 to 7,000 gallons, depending on the wall height and model.
On this page (7 sections)
Intex rates the Easy Set 18 ft × 48 in at 5,455 gallons, the Greywood Prism Frame 18 ft × 48 in at 6,423 gallons, and the Ultra XTR Frame 18 ft × 52 in at 6,981 gallons.
Quick answer: 18 ft round pool gallons by wall height
Geometry at 90% fill gives 6,853 gallons for a 48 in wall, 7,424 for 52 in, and 7,709 for 54 in (the "18x54" size). No real pool in our list reaches its geometric number, so the table below also shows estimates for frame and inflatable pools. For an 18 × 54 frame pool of unknown brand, start from 7,170 gallons.
| Wall height | Geometry | Frame pool estimate (× 0.93) | Inflatable estimate (× 0.87) |
|---|---|---|---|
| 42 in wall | 5,996 gal22,698 L | 5,576 gal | 5,217 gal |
| 48 in wall | 6,853 gal25,941 L | 6,373 gal | 5,962 gal |
| 52 in wall | 7,424 gal28,102 L | 6,904 gal | 6,459 gal |
| 54 in wall | 7,709 gal29,183 L | 7,170 gal | 6,707 gal |
Geometry = π/4 × diameter² × water depth × 7.48. Real pools hold less than the nominal size suggests. The factors are medians of 26 manufacturer capacities (our own calculation).
| Model | Capacity | Fill basis | Real ÷ nominal geometry | Source |
|---|---|---|---|---|
| Intex Easy Set 18ft x 48in | 5,455 gal20,649 L | 80% fill | 0.896 | manufacturer |
| Intex Greywood Prism Frame 18ft x 48in | 6,423 gal24,314 L | 90% fill | 0.937 | manufacturer |
| Intex Ultra XTR Frame 18ft x 52in | 6,981 gal26,426 L | not stated | 0.940 | manufacturer |
| Coleman Power Steel Swim Vista 18ft x 48in | 6,092 gal23,061 L | 90% fill | 0.889 | not confirmed |
| Change | Amount |
|---|---|
| +1 ppm FC (12.5% liquid chlorine) | 6.5 fl oz193 mL |
| +10 ppm TA (baking soda) | 14.3 oz405 g |
| +10 ppm CYA (stabilizer) | 8.5 oz241 g |
Closest full chart: 6,000 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.
Manufacturer capacities for this size
"18 × 48" on the box does not tell you the volume. Two Intex 18 × 48 pools differ by 968 gallons: the Easy Set, rated at 80% fill with an inflatable top ring, holds 5,455, and the Greywood Prism Frame, rated at 90%, holds 6,423. That is 18% more water, and 18% more of every chemical. The Coleman Power Steel Swim Vista 18 × 48 is listed at 6,092 gallons, but we found that number only on retailer pages, not from the manufacturer, so treat it as unconfirmed (more on Coleman Power Steel pool gallons). The Ultra XTR's page doesn't state a fill level. Its 6,981 gallons is 0.940 of the geometric volume for a 52 in wall at 90% fill, which suggests the same 90% basis.
Starting doses for this volume
| Change | Easy Set 18 × 48 (5,455 gal) | Greywood Prism 18 × 48 (6,423 gal) | Ultra XTR 18 × 52 (6,981 gal) |
|---|---|---|---|
| +1 ppm free chlorine (FC), 12.5% liquid chlorine | 5.6 fl oz | 6.6 fl oz | 7.1 fl oz |
| +1 ppm FC, 6% household bleach | 11 fl oz | 13 fl oz | 14 fl oz |
| +10 ppm alkalinity (TA), baking soda | 12.2 oz | 14.4 oz | 15.6 oz |
| Stabilizer (CYA), 0 to 30 ppm | 1.35 lb | 1.6 lb | 1.75 lb |
| Salt to 3,200 ppm (new salt pool) | 146 lb | 172 lb | 186 lb |
Salt in 40 lb bags: buy four, five, and five bags, then add the exact weight from the table, not the whole last bag. Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling.
Full charts with shock and acid amounts: 6,000 gallons for the Greywood and 7,000 gallons for the Ultra XTR.
Calculator: your exact depth
Enter 18 ft and your wall height. For an Easy Set, choose "Inflatable ring" and set the fill to 80% to match Intex's rating, or enter your own level. For steel-wall and frame pools, choose "Metal frame" and enter your measured level.
Chemicals per week for this size (estimate from your own loss)
At this size and up, most owners buy liquid chlorine by the gallon. With a daily loss of 2 ppm, the Greywood Prism Frame needs about 92 fl oz of 12.5% chlorine a week. At 3 ppm a day, it needs about 1.1 gallons. Measure your own drop for a few days before buying: test at the same hour, note the weather, and divide the total drop by the number of days. Liquid chlorine loses strength in storage, faster when it is warm, so a supply for more than a few weeks will be weaker by the time you use it. Weekly routines for this size: above-ground pool care.
Safety. Keep chlorine and acid in separate, closed containers in a cool, shaded place. Add each directly to the pool with the pump running, never pre-mixed. Poison Control: 1-800-222-1222.
FAQ
How many gallons is an 18x48 above ground pool?
5,455 gallons for the Intex Easy Set (80% fill) and 6,423 for the Intex Greywood Prism Frame (90% fill). Plain geometry at 90% fill gives 6,853. Our estimate for a frame pool of unknown brand is 6,373.
How many gallons is an 18x52 above ground pool?
Intex rates the Ultra XTR Frame 18 ft × 52 in at 6,981 gallons. Plain geometry at 90% fill gives 7,424, and our estimate for a frame pool of unknown brand is 6,904.
How much chlorine for an 18 ft pool?
Per 1 ppm: 5.6–7.1 fl oz of 12.5% liquid chlorine, or 11–14 fl oz of 6% bleach, depending on the model. To raise FC from 1 to 4 ppm in the Greywood, you need about 20 fl oz of 12.5% chlorine.
How long does it take to fill an 18 ft pool?
For 6,423 gallons: about 21 hours at 5 gallons per minute, or 11 hours at 10. Check the rate on your water bill: for each $1 per 1,000 gallons, the fill costs about $6.42.
Sources
- Intex Easy Set 18 ft × 48 in, read 2026-09-29: intexcorp.com
- Intex Greywood Prism Frame 18 ft × 48 in, read 2026-09-29: intexcorp.com
- Intex Ultra XTR Frame 18 ft × 52 in, read 2026-09-29: intexcorp.com
- Coleman Power Steel Swim Vista 18 ft × 48 in, retailer listing only (not confirmed by the manufacturer): lowes.com
- Volume formulas, correction factors, and dose math: methodology