Measure a round pool across the center of the top rail for its diameter, or an oval pool for full length by width, then match the cover to that exact size.
One tape measure pulled corner to corner instead of straight across the middle is the difference between a cover that seals the water in and one that sags into it by January. Getting the numbers right for an above ground pool cover takes about ten minutes on the deck, but it has to survive a winter of snow load, wind, and roughly 18 inches of water dropping out from underneath it. The steps below cover what to measure, which cover size the numbers point to, and the two compatibility details that quietly decide whether the cover stays put.
What Do You Actually Measure On A Round Above Ground Pool?
For a round pool, measure the diameter across the center of the pool’s top, from one outside edge of the top rail to the other. That single number — not the water surface, and not the number printed on the pool’s box — decides which round cover fits.
Pull the tape straight across the middle so it passes over the exact center point of the pool; a tape stretched off-center reads short and sends you to the wrong size. Measure to the outside of the pool wall or top rail, never to the inside of the water’s edge. Above-ground covers are listed by pool size from inside edge to inside edge, and the cover itself is cut larger than the pool on purpose.
That extra material is the overlap. Weighing a cover down by its overlap is part of what keeps wind from lifting an edge and opening a gap to the water below.
How Do You Measure An Oval Pool Instead?
An oval above ground pool needs two measurements: the full length end to end and the full width across the middle. Both come off the outside edges, not the water line.
Oval covers are sold as a length × width pair, and the shape must match the pool. Common oval sizes include 12 x 24, 15 x 30, 16 x 25, 16 x 32, 18 x 33, and 21 x 41 feet. The first number is always the longer dimension, so keep length and width straight when you write the numbers down.
Two things go wrong here. First, measuring over the pool’s highest point or along a curve instead of a straight line across the middle inflates the reading. Second, assuming the nominal size on the pool’s paperwork matches the outside measurement — it often doesn’t. A pool sold as a 15 x 30 can measure slightly different at the rail, and the cover follows the measurement, not the label.
Does Top Rail Size Change Which Cover You Buy?
Top rail width is the detail most buyers skip, and it’s the one that decides whether a correctly measured cover actually overlaps far enough. Wide rails eat into the overhang, so the standard 3-to-4-foot overlap may not reach the ground on every pool.
The rule is simple: a pool with a 7-inch to 9-inch top rail needs a cover built with 4 feet of overlap rather than 3. A pool with an extra-large top rail of 10 inches or more usually needs the next pool size up, because the wider rail shortens how far the cover hangs. Too little overlap means the cover can’t be secured properly once wind and water weight start working on it.
Shape matters just as much as size. Matching a cover to the pool’s gallon capacity or its approximate area will lead you to a cover that’s the right general scale and the wrong actual shape — a round cover on an oval pool leaves corners exposed no matter how much overlap it has. Measure the shape you have, then buy for that shape.
Round And Oval Sizes At A Glance
| Pool Shape | What To Measure | Typical Listed Sizes |
|---|---|---|
| Round | Diameter across the center, outside edge to outside edge | 12′, 15′, 18′, 21′, 24′, 28′, 30′, 33′ |
| Oval | Full length end to end, plus full width across the middle | 12 x 24, 15 x 30, 16 x 25, 16 x 32, 18 x 33, 21 x 41 |
| 7″ to 9″ top rail | Diameter or length × width, same as above | Choose a 4′ overlap instead of 3′ |
| Top rail 10″ or wider | Diameter or length × width, same as above | Order the next pool size up |
| Water surface only | Wrong method — reads short | Do not use for ordering |
| Nominal pool label | Wrong method — often off from the rail measurement | Do not use for ordering |
| Round cover on oval pool | Shape mismatch | Leaves corners uncovered |
Once the numbers are on paper, the remaining choice is which cover to actually buy. The tested above ground pool cover roundup breaks down the current picks by shape and size.
How Much Should You Expect To Pay?
Above ground pool covers generally run from about $35 to $1,000 depending on size, material, and whether it’s a winter, solid, solar, or all-season cover. Larger round and oval sizes sit at the top of that range.
Intex lists its pool cover line and replacement covers separately, and its catalog pages carry current pricing as sizes and materials change. Intex’s above-ground pool cover catalog is the official reference for listed sizes.
Write your two measurements down before you shop, and keep the shape and top rail width next to them. Those three lines rule out every cover that won’t fit and leave you choosing between materials and price instead of guessing at size.
Common Questions
Can I Just Use The Pool’s Listed Size To Order A Cover?
Rarely without checking first. Pool labels reflect nominal dimensions, and the actual outside measurement at the top rail often differs by a few inches. Measure the pool yourself, then compare that number to the cover maker’s listed sizes. If the two are close but not exact, trust your tape measure over the pool’s paperwork.
Why Do Covers Come So Much Bigger Than The Pool?
The extra material is deliberate overlap, usually 3 to 4 feet per side. It drapes past the top rail and down toward the ground so water dropping roughly 18 inches during winterization doesn’t pull the cover taut and expose the surface. Buyers with a 7-inch to 9-inch top rail should look for the 4-foot overlap version.
What If My Pool Doesn’t Match A Standard Listed Size?
Most round and oval pools fall into the standard size ladder, so measure carefully before assuming you’re outside it. Recheck that the tape crossed the true center and reached the outside edge. If the pool genuinely sits between two listed sizes, the larger one gives you more overlap to work with rather than too little.
Sources
- Intex. “Above Ground Pool Covers” Official catalog listing round and oval cover sizes, current prices, and model numbers.
- Intex. “Above Ground Pool Covers — Replacement Parts” Replacement cover sizing and compatibility reference for round and oval above-ground pools.