Your winter pool cover size should be about 4-5 feet larger than your pool in both length and width. A 15 ft round above-ground pool needs a cover roughly 19-20 ft across. Measure the longest and widest points, include steps, then round up to the next size sold. Inground pools and lowered water levels need extra.
Winter pool cover size chart by pool size
Start with the rule: finished cover size = pool size + 4 to 5 ft in each direction. The extra fabric hangs over the wall or lies on the deck so the cover can be tied down.
One trap catches many buyers. Some retailers label a cover by the pool it fits (“fits 15 ft round”). Others label it by the finished fabric size (“20 ft cover”). Read the product description before you compare sizes.
| Your pool | Approximate finished cover size |
|---|---|
| 12 ft round | 16-17 ft round |
| 15 ft round | 19-20 ft round |
| 18 ft round | 22-23 ft round |
| 21 ft round | 25-26 ft round |
| 24 ft round | 28-30 ft round |
| 27 ft round | 31-32 ft round |
| 30 ft round | 34-35 ft round |
| 12 x 24 ft oval | about 16 x 28 ft |
| 15 x 30 ft oval | about 19 x 34 ft to 20 x 35 ft |
| 18 x 33 ft oval | about 22 x 37 ft |
These are typical ranges, not a spec. Fabric sizes vary by brand, so check the maker’s size table for your model.
How to measure your pool for a winter cover
You need two numbers for any pool: the longest length and the widest width. Use a long tape measure and a helper so the tape stays straight and level.
- Round pool: measure straight across the center from inside wall to inside wall. Do not measure around the edge.
- Oval, rectangle or freeform pool: measure the longest dimension end to end, then the widest dimension at a right angle to it.
- Include steps, ledges and built-in seating inside those two measurements. If a step sticks out past the main body, the cover has to reach it.
- Measure twice and write down feet and inches. A 15 ft 6 in pool is not a 15 ft pool.
- Add 4-5 ft to each number for the finished size, or match your numbers to the pool-size label if the listing uses that system.
- Round up. If your size is not sold, buy the next size up, not the next size down. A cover that comes up short leaves a gap that water, leaves and wind will find.
Do not size from a solar cover. Solar covers fit the pool closely with little overlap, so their size will leave you too small.
Sizing round, oval, rectangle and freeform pools
Round and oval
Round pools are easy: diameter plus 4-5 ft. Ovals work the same way, applied to both the length and the width. A 15 x 30 ft oval needs about a 19-20 x 34-35 ft cover.
Rectangles with Roman ends or rounded corners
Measure the full length at the longest point and the width at the widest point. Rounded corners do not reduce the size you need. Cover makers use a rectangle that holds the whole shape.
Kidney and freeform pools
Picture the smallest rectangle that would hold your pool, then measure that rectangle.
Worked example: a kidney-shaped pool is 30 ft long including a 3 ft step area. It is 16 ft across at the widest lobe. The bounding rectangle is 30 x 16 ft. Add 4-5 ft to each and you need roughly 34-35 x 20-21 ft. If the nearest listed size is a little larger in both directions, take it. If it is larger in only one direction, it is too small.
Pools next to a wall, deck or spa spillover
A standard rectangular cover does not seal well around a raised spa, a wall or a deck that cuts into the pool outline. Measure to the obstruction and call the cover maker. You may need a custom cover.
Above-ground vs inground: how the overhang changes
Above-ground pools. The cover drapes over the top rail and down the wall. A cable runs through grommets around the cover edge and a winch tightens it under the rail. About 4-5 ft total (2-2.5 ft on each side) is the usual allowance. Use the diameter measured at the inside of the wall, not the outside of the top rail.
Inground pools. The cover floats on the water and extends onto the deck, where it is held down by water tubes, water bags, or deck anchors. Many inground covers also run 4-5 ft larger, but some brands and securing methods call for 5 ft or more. Wide coping or a raised bond beam may call for more. This depends on the brand and model, so check the maker’s chart.
Before you close the pool, clean it. A debris-free pool stays clearer through winter and opens faster in spring. If you are due for a new cleaner, see our picks for robotic above-ground pool cleaners or robotic cleaners for inground pools.
Do you need a bigger cover if you lower the water?
Yes, if the water will sit well below its normal level. The cover has to reach down into the pool as well as across it, which uses up fabric. Retailers suggest adding extra size when the water drops more than about 1 ft below normal. One retailer’s rule is to double the distance beyond the first foot.
Worked example: water 20 in below normal is 8 in past the 1 ft mark. Doubling that gives 16 in, so add about 1.3 ft to the length and width on top of the normal 4-5 ft.
Most owners should not need this. Many pool makers advise only a small drop, often to just below the skimmer or return, for a solid cover. Draining too far can wrinkle or shift a vinyl liner and, in some pools, stress the walls. Follow the pool manufacturer’s winterizing instructions for your liner and pool type. Your local pool pro can tell you what works in your climate.
Winter cover vs safety cover, and how to keep it on
A tarp-style winter cover keeps out leaves and sunlight. It is not a safety cover. It will not hold a child, a pet or an adult, and standing water and debris on top can hide the pool. Keep people and animals off it and away from the pool edge, and clear standing water with a cover pump.
Safety covers use a different sizing system. They are made to your pool’s exact measurements and anchored into the deck. If you need one to meet local rules, look for ANSI/ASTM F1346 compliance and check your local code.
| Securing method | Best for | Notes |
|---|---|---|
| Cable and winch | Above-ground pools | Standard with many covers. Tighten it again after the first storm. |
| Water bags or tubes | Inground pools, some above-ground | Fill about three-quarters full so freezing ice can expand without splitting them. |
| Wall bags | Above-ground pools | Hold the edge against the wall, usually used with a cable. |
| Deck anchors with safety cover | Inground pools | Custom sizing, highest cost, needs drilled anchors. |
Common winter cover sizing mistakes
- Buying the pool size when the listing uses finished cover size, or the reverse.
- Measuring around a round pool instead of straight across.
- Leaving steps or ledges out of the length.
- Rounding down to a smaller size because it is cheaper.
- Sizing from a solar cover.
- Lowering the water far past the normal level without adding cover size.
- Ignoring a wall, spa or deck that changes the pool outline.
If you are unsure between two sizes, pick the larger one. A little extra fabric is easy to secure. A cover that is too short is not fixable.
Frequently Asked Questions
Can I use a cover that is bigger than the chart suggests?
A little extra is fine. Going 1-2 ft over the recommended size leaves more edge to tie down. Much larger covers get heavy, catch wind and bunch up. Choose the closest size that fully covers both your length and width.
Should I buy a solid or mesh winter cover?
Solid covers block sunlight and keep debris out, which helps keep water clearer, but water pools on top and needs pumping. Mesh drains rain and snowmelt but lets in fine dirt and some light. Safety covers come in both styles.
Can I use my solar cover over winter?
No. Solar covers are thin, fit the pool closely and are not built for snow, ice or wind. Take it off, clean and dry it, and store it. Use a winter cover that is 4-5 ft larger than the pool.
Do I need a cover pump?
For a solid cover, yes. Rain and snowmelt collect on top, adding weight and stressing the edges. A small cover pump removes standing water. It also lowers the risk of a hidden drowning hazard on the surface.
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