Pick your pool's shape and measure the water, wall to wall. You get the stock solar blanket to buy and how much to trim off each side, from a cover maker's own size chart and its own cutting instructions.
Your solar blanket
Buy an 18-ft round solar blanket for a 16 ft round pooltrim 12″ all round · it covers 201 sq ft of water
Quick answer: measure the water wall to wall and buy the stock solar blanket of that size, or the next size up, then trim it to the walls. A 16 ft round pool takes an 18-ft round blanket, trimmed 12″ all round; a 15 × 30 ft rectangle takes a 16 × 32 ft blanket, 6″ off each side and 12″ off each end. Blue Wave’s own steps: float it 2 to 4 days, mark the walls, cut it big, then trim again.
How to use the solar pool cover size calculator
- Pick the pool’s shape: round, oval, rectangle or free-form.
- Measure the water, inside wall to inside wall: straight across a round pool, the widest and longest of any other. Feet and inches work: 15′ 6″.
- Read the blanket to buy and how much to trim off each side, with the maker’s cutting steps.
The drawing puts your pool inside the blanket as it comes, to scale, so you can see what comes off.
The rule, and where it comes from
The sizes. Blue Wave’s 2026 pool product catalog lists its solar blankets in round 12, 15, 18, 21, 24, 27, 28, 30 and 33 ft; oval 12 × 18, 12 × 24, 15 × 30, 16 × 32 and 18 × 33 ft; and rectangle 12 × 20, 12 × 24, 14 × 28, 16 × 24, 16 × 32, 18 × 36, 20 × 40, 20 × 44 and 24 × 40 ft. The calculator picks the smallest of them that covers your water.
The trim. Blue Wave’s installation instructions: the cover goes on bubbles down and is “left floating in the pool for 2 to 4 days to remove the packaging creases”. Then “make an outline of your pool walls with a marker”, take it out to cut, away from the liner, and “cut the cover larger than necessary, then give it a final trimming for an exact fit after a day or two”. It “can be cut easily with household scissors to fit the angles and curves of the pool walls”.
The heat. Blue Wave says its blankets can raise the water “as much as 15ºF”. Pentair’s heater sizing notes that a pool “will usually lose 2–4°F. per day” in cooler weather, the loss a blanket is there to cut.
Solar blanket sizes: which one fits your pool
| Your pool | Blanket to buy | Trim |
|---|---|---|
| 12 ft round | 12-ft round | no trimming beyond the ladder and the fittings |
| 15 ft round | 15-ft round | no trimming beyond the ladder and the fittings |
| 16 ft round | 18-ft round | trim 12″ all round |
| 18 ft round | 18-ft round | no trimming beyond the ladder and the fittings |
| 20 ft round | 21-ft round | trim 6″ all round |
| 24 ft round | 24-ft round | no trimming beyond the ladder and the fittings |
| 15 × 30 ft oval | 15 × 30 ft oval | no trimming beyond the ladder and the fittings |
| 14 × 27 ft oval | 15 × 30 ft oval | trim 6″ off each side and 18″ off each end |
| 16 × 32 ft rectangle | 16 × 32 ft rectangle | no trimming beyond the ladder and the fittings |
| 15 × 30 ft rectangle | 16 × 32 ft rectangle | trim 6″ off each side and 12″ off each end |
| 20 × 40 ft rectangle | 20 × 40 ft rectangle | no trimming beyond the ladder and the fittings |
From Blue Wave’s size chart (its 2026 catalog). Other makers sell similar sizes; check theirs against your measurement the same way.
Worked examples
Buy an 18-ft round solar blanket for a 16 ft round pool: no 16-ft round in Blue Wave’s range, so the next size up, trimmed 12″ all round.
Buy a 15 × 30 ft oval solar blanket for a 14 × 27 ft oval pool: 6″ off each side and 18″ off each end.
Buy a 16 × 32 ft rectangle solar blanket for a 15 × 30 ft pool: 6″ off each side, 12″ off each end.
Buy an 18 × 36 ft rectangle solar blanket for a 17 × 35 ft free-form pool: a kidney or free-form pool takes a rectangle, cut to its walls.
Common mistakes
- Measuring the deck, not the water. The blanket floats on the water inside the walls: measure wall to wall.
- Cutting on the first day. Blue Wave: float it 2 to 4 days so the packaging creases come out before you mark the walls.
- Cutting in the pool. Scissors can cut the liner: mark the walls, lift the blanket out, then cut.
- Cutting it exact the first time. Cut it a little big, and trim again after a day or two.
- Bubbles up. The bubbles go down, on the water.
- Treating it as a safety cover. It is not one: Blue Wave warns that someone can be caught under it and drown. It comes right off before anyone swims.
More on pools at Dreamy Home Style
Heating it too? The pool heater size calculator gives the hours to heat. A winter or mesh safety cover is a different product: the pool safety cover size calculator sizes it. To plan the yard around the pool, use the free 2D floor planner.
Solar pool cover questions
What size solar cover do I need for my pool?
The size of the water, wall to wall, or the next stock size up, trimmed to the walls. A 16 ft round pool takes an 18-ft round blanket, trimmed 12″ all round.
What size solar cover for an above ground pool?
The pool’s own size if a maker sells it: an 18 ft round pool takes an 18-ft round blanket. Blue Wave’s rounds are 12, 15, 18, 21, 24, 27, 28, 30 and 33 ft.
Should a solar pool cover be bigger than the pool?
Only as much as you will trim off. Blue Wave’s steps: float it 2 to 4 days, mark the walls, cut it a little big, then trim it to an exact fit after a day or two.
How do you cut a solar pool cover to fit?
Float it bubbles down for 2 to 4 days, outline the pool walls on it with a marker, lift it out and cut away from the liner with household scissors, then trim again a day or two later.
Can I use a rectangle solar cover on a round or oval pool?
Yes, cut to the walls. Blue Wave says its covers cut “to fit the angles and curves of the pool walls”. It is the way to cover a kidney or free-form pool.
Which side of a solar cover goes down?
The bubble side goes down on the water, the smooth side up (Blue Wave’s instructions).