Pool pillow size calculator
What size winter air pillow your above-ground pool needs, and how many. Pick round or oval, enter the size, and get the pillows that cover about 10% of the water.
What size air pillow does your pool need?
Pillows are labelled by round pool diameter, which tells an oval owner nothing. This works from your pool's surface area instead, using In The Swim's rule: enough pillow to cover about 10% of the water.
Then fill it only 50–70%. POOLHACKER's instructions give that range and Leslie's says about halfway; a full pillow is the one that splits. On an oval, space the pillows along the long axis and tie them to opposite rails so they cannot drift to one end. Expect one to be flat by spring — Trouble Free Pool's closing page says pillows "often don't stay inflated for the season." Which ones hold air longest: the air pillow showdown.
Pool pillow size chart: round pools
| Pool | Water surface | Pillow needed (10%) | Pillows (share of the water covered) |
|---|---|---|---|
| 12 ft round | 113 sq ft (10 m²) | 11 sq ft (1.0 m²) | one 4×4 (14%) |
| 15 ft round | 177 sq ft (16 m²) | 18 sq ft (1.7 m²) | two 4×4s (18%) |
| 18 ft round | 254 sq ft (24 m²) | 25 sq ft (2.3 m²) | two 4×4s (13%) |
| 21 ft round | 346 sq ft (32 m²) | 35 sq ft (3.3 m²) | three 4×4s (14%), or one 8×8 (18%) |
| 24 ft round | 452 sq ft (42 m²) | 45 sq ft (4.2 m²) | three 4×4s (11%), or one 8×8 (14%) |
| 27 ft round | 573 sq ft (53 m²) | 57 sq ft (5.3 m²) | four 4×4s (11%), or one 8×8 (11%) |
| 30 ft round | 707 sq ft (66 m²) | 71 sq ft (6.6 m²) | five 4×4s (11%), or one 8×8 + one 4×4 (11%) |
| 33 ft round | 855 sq ft (79 m²) | 86 sq ft (8.0 m²) | six 4×4s (11%), or one 8×8 + two 4×4s (11%) |
Oval pools
| Pool | Water surface | Pillow needed (10%) | Pillows (share of the water covered) |
|---|---|---|---|
| 12×24 ft oval | 257 sq ft (24 m²) | 26 sq ft (2.4 m²) | two 4×4s (12%) |
| 15×30 ft oval | 402 sq ft (37 m²) | 40 sq ft (3.7 m²) | three 4×4s (12%), or one 8×8 (16%) |
| 16×32 ft oval | 457 sq ft (42 m²) | 46 sq ft (4.3 m²) | three 4×4s (11%), or one 8×8 (14%) |
| 18×33 ft oval | 524 sq ft (49 m²) | 52 sq ft (4.8 m²) | four 4×4s (12%), or one 8×8 (12%) |
| 18×40 ft oval | 650 sq ft (60 m²) | 65 sq ft (6.0 m²) | four 4×4s (10%), or one 8×8 (10%) |
Why this works from area, not the label
Pool pillows are sold by round-pool diameter, so the box answers one question for one shape. In The Swim's guidance is the only rule we found that works for every pool: "buy enough air pillows to cover about 10% of your pool surface area." The calculator takes your pool's area and finds the fewest of the two sizes we rank, 4×4 and 8×8, that reach it. It shows the share of the water each answer covers, and on a close call what one fewer pillow would cover, so you can see how near the line you are.
One thing most oval charts get wrong: an above-ground oval is not an ellipse. It has straight sides, and an ellipse formula under-counts an 18×33 by nearly 60 sq ft, which is the difference between three 4×4 pillows and four. Our pool volume calculator uses the same straight-sided shape.
What a pillow is for
- It holds the cover up. Rain and snow run off to the edges instead of pooling in a sagging middle, where the weight can pull the cover into the pool.
- The ice claim is the maker's. Blue Wave calls it "Ice Equalization" and Swimline calls its pillows "ice compensators"; nobody independent has shown a pillow protects the wall. Protect the pool from ice by lowering the water below the skimmer.
- Tie it off. Run rope from the pillow's grommets to the rails so it stays centred, or on an oval spaced along the long side.
Next: the air pillow showdown ranks which pillows actually hold air, and above-ground winter covers and air pillows matches the cover to your pool's wall.
Sizing rule: In The Swim (intheswim.com). Fill guidance: POOLHACKER instructions, Leslie's. The "often don't stay inflated" line: Trouble Free Pool, "Closing (Winterizing) Your Above Ground Pool".
FAQ
What size pool pillow do I need for a 24 ft round pool?
A 24 ft round pool has about 452 sq ft (42 m²) of water, so In The Swim's 10% rule asks for about 45 sq ft (4.2 m²) of pillow: three 4×4s, or one 8×8.
What size pool pillow do I need for an 18 ft round pool?
About 25 sq ft (2.3 m²) of pillow for 254 sq ft (24 m²) of water: two 4×4s, which covers 13%. One 4×4 alone covers 6%.
How many pool pillows do I need for a 15x30 oval pool?
A 15×30 above-ground oval has about 402 sq ft (37 m²) of water (straight sides and round ends), so about 40 sq ft (3.7 m²) of pillow: three 4×4s, or one 8×8. Space them along the long side and tie them to opposite rails.
What size pool pillow for a 30 ft round pool?
About 71 sq ft (6.6 m²) of pillow: five 4×4s, or one 8×8 + one 4×4.
How full should a pool pillow be?
Half to two-thirds full, never tight. POOLHACKER tells owners to inflate to 50–70% and Leslie's says about halfway, to leave the pillow room to squeeze as ice forms. A fully inflated pillow is the one that splits.
Do pool pillows protect an above-ground pool from ice?
The makers say so, and nobody independent has shown it. Pillows also often go flat mid-winter. Buy one for the job that is not in dispute: holding the cover up so rain and snow run to the edges instead of pooling in the middle.