How to Measure Your Pool for the Right Cover Size
Measure the water, never the deck. Stretch a tape measure across the pool at the longest and widest points, going strictly from inside wall to inside wall. Taking measurements from the outer stone edge is an easy mistake, but that leaves you with a sagging cover that dumps dirty debris straight into clean water.
The exact size you order depends on the cover style and your pool layout. A floating solar blanket must match the inner walls closely, while a seasonal winter tarp needs several feet of extra overlap over the edge. Walk-in stairs, rounded corners, and above-ground rails also change how you calculate the dimensions. Here is how to measure every edge properly so you get a clean fit without any guesswork.
The Short Version
- Measure the inside pool walls at the waterline (the inner pool wall where the water touches) at the longest and widest points, never the deck or outer patio.
- Add overlap (extra fabric extending beyond the pool edge onto the deck or down the wall) depending on your cover type: none for floating solar blankets, 1 to 2 feet on all sides for tensioned safety covers, and 3 to 4 feet for standard solid winter tarps.
- Confirm that you have at least 3 feet of solid deck space around the pool perimeter if you plan to install anchor-based safety covers.
- Check for fixed obstacles like ladders, grab rails, slide legs, and raised spa walls before placing an order so the cover fits without tearing.
What to Measure First: The Wall-to-Wall Rule
The biggest mistake pool owners make is pulling a tape measure across the patio deck or over the coping (the finished stone or concrete edge directly around the pool). When you buy a pool cover, the manufacturer needs to know the exact footprint of the water itself. The coping and deck do not tell you how much water surface you need to shield.
Always measure from inside wall to inside wall right at the waterline. Keep your tape measure flat and straight across the span. If your pool has rounded top edges or bullnose tile, drop your measurement down to the vertical wall surface inside the pool. This gives you the true width and length of the pool shell.
For an above-ground pool, measure from the inside face of the top rail on one side to the inside face of the top rail directly across. Do not measure down the outside metal siding or wrap the tape under the outer rim. Taking the inside dimensions guarantees the cover rests where it belongs without pulling against the frame.
Adding Overlap: Calculating Total Cover Size by Style
Once you have your exact pool measurements, the type of cover you choose dictates how much extra material you need. Different covers serve different purposes, and their sizing rules vary completely.
Floating Solar Covers: Solar blankets sit directly on top of the water inside the pool walls. They do not use anchors, ropes, or water bags. For these, you need zero extra overlap. If your pool is 16 feet by 32 feet, you buy a 16 by 32 foot solar cover. If you cannot find an exact match, buy the next standard size up and trim the edges with household scissors so the plastic bubbles rest flat on the water.
Tensioned Safety Covers: Safety mesh covers use heavy-duty straps hooked into brass deck anchors. These covers must extend past the pool edge onto the concrete deck by 12 to 18 inches on all sides. Most safety cover companies sell their covers by pool size, meaning a cover labeled for a 16 by 32 foot pool already includes that built-in overlap. Always verify the product listing before ordering to confirm whether the advertised dimension refers to the pool size or the finished cover size.
Solid Winter Tarps: Winter tarps for inground pools need substantial slack because winterizing requires dropping the pool water several inches below the skimmer. The tarp must drape over the coping, drop down the inside wall, and rest on top of the water so ice and snow do not rip the material. You need 3 to 4 feet of overlap around the entire perimeter. If you have an above-ground pool, look for covers with at least 3 to 4 feet of overhang so the cable and winch can clamp tightly beneath the top rail.
Leaf Net Covers: Leaf nets are lightweight screens that stretch over a main winter cover to catch fallen leaves during autumn. You want an overlap of 2 to 3 feet so you can anchor the edges with water tubes or stakes. Keeping debris off your winter setup makes spring opening much faster. If you already use a mechanical roller, learning how to clean an automatic pool cover safely can help protect the fabric from early wear.
Step-by-Step Measuring for Rectangular and Round Pools
Measuring standard pool shapes is simple if you take your time and work with a helper. Avoid stretchy fabric sewing tapes. Use a long fiberglass tape measure that stays straight when pulled across the yard.
- Measure the full length: Place the end of the tape against the inside wall at the shallow end. Run the tape across to the inside wall at the deep end. Keep the tape taut and record the distance in feet and inches.
- Measure the width at three points: Measure from inside wall to inside wall at the shallow end, in the middle, and at the deep end. Pools can shift or settle over time. If your widths vary by an inch or two, use the widest measurement to make sure your cover gives full coverage.
- Check the corners: Look at your pool corners. Note whether they are square 90-degree corners, rounded radius corners, or cut at an angle (diagonal corners). If they are rounded, measure the radius by placing a framing square on the deck corner and measuring from the corner of the tool to where the curve touches the straight wall.
- Measure diagonals for squareness: On rectangular pools, measure from the top-left corner to the bottom-right corner, then measure from the top-right corner to the bottom-left corner. If both diagonal numbers match, your pool is perfectly square. If the numbers differ by several inches, your pool is slightly out of square, which safety cover manufacturers must know.
- Measure round pools across the center: For round pools, measure across the widest point through the center from inside wall to inside wall. Take three separate cross-measurements at different angles, like the hands of a clock pointing to 12, 2, and 4. If all three numbers match, your pool is a true circle. If one measurement is longer, your pool may be slightly oval.
How to Measure Walk-In Steps, Swim-Outs, and Freeform Curves
Pools with built-in features require extra attention. Built-in stairs, swim-out benches, and kidney shapes cannot use a standard off-the-shelf rectangle without custom shaping or extra overlap coverage.
- Locate and measure built-in steps: Identify where your steps sit. Are they centered on the end wall, or are they offset to the left or right? Measure the width of the step opening where it joins the pool wall, and measure how far the steps extend outward from the main pool wall onto the deck.
- Note step shape and corners: Look at the front of the steps. Standard steps are rectangular, while Roman steps curve outward in a half-circle. Measure the depth of the curve from the pool edge to the farthest point of the arc.
- Measure swim-outs and sun shelves: Swim-outs are small deep-end benches, while sun shelves are shallow ledge areas. Measure their length, width, and exact distance from the nearest pool corner. You must treat these as extensions of the main pool waterline.
- Use the bounding box method for simple curves: For kidney or oval pools using a winter tarp, measure the longest point from tip to tip and the widest point across the belly. Pretend the pool is inside a giant imaginary rectangular box. Buy a cover sized to that total box dimension so the tarp covers all curves with room to spare.
- Use triangulation for custom safety covers: If you are ordering a custom-fit safety cover for a freeform pool, you will need triangulation (measuring from two fixed points to pinpoint curved edges). Mark two permanent reference points (point A and point B) on your concrete deck at least 15 to 20 feet apart. Walk around the pool perimeter and use chalk to mark points along the waterline every 2 to 3 feet. Measure the distance from point A to chalk mark 1, then from point B to chalk mark 1. Repeat this for every numbered chalk mark. The cover maker uses these paired coordinates to map your pool curves into a computer program.
Critical Measuring Traps to Double-Check Before Buying
A few small oversights can ruin an otherwise accurate measurement. Run through this quick checklist before you click the order button:
- Check for non-removable handrails and ladders: If handrails or ladder legs sit right at the pool edge and cannot be unscrewed, your cover needs custom cutouts. Measure how far the handrail sockets sit from the waterline.
- Confirm deck space for anchors: Safety covers need at least 3 feet of solid, unobstructed concrete or paver deck around the pool. If you have grass, flowerbeds, or a fence within 3 feet of the water, standard brass anchors will not work without lawn stakes or cable systems.
- Account for raised walls and rock waterfalls: If your pool features a raised spa wall, sheer descent waterfall, or rock feature that rises above the coping, a flat cover cannot stretch past it. Note the height and length of the raised section so the manufacturer can supply wall-mount hardware.
- Account for the winter water drop: If you drain your pool water below the skimmer by 12 to 18 inches, remember that a solid winter tarp must dip down into the pool. If your tarp is too tight, the weight of winter snow will pull the water bags or straps right into the pool. When in doubt on a winter tarp, buy the next size larger.
Helpful Tools and Accessories for Winterizing and Cover Setup
Measuring accurately is the foundation, but having the right closing equipment makes installing your cover straightforward and protects your investment through cold weather.
When securing safety covers, specialized cover installation rods give you the leverage needed to stretch thick tension springs over recessed deck anchors without pinching your fingers or straining your back. Look for sturdy stainless steel rods around 26 to 29 inches long that resist bending under tension and fit standard anchor posts.
Before pulling any heavy winter tarp across the pool, prepare the plumbing lines so the cover does not have to be lifted later. Push-in skimmer plugs seal the skimmer throat directly from inside the pool, keeping rain and snow out of the pipes without requiring tools or full pool draining. Pairing your solid winter tarp with a fine-mesh leaf net cover allows you to catch autumn foliage and pull it away in minutes before freezing weather sets in, keeping your main cover clean and balanced all winter.
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FAQs
Do I measure my pool with the water level lowered for winter?
No, you should always measure the pool shell from inside wall to inside wall regardless of where the water sits. The physical dimensions of the concrete, vinyl, or fiberglass walls remain the same whether the pool is full or partially drained. You account for the lower winter water level by adding extra overlap to your tarp size, not by changing your baseline pool measurements.
What should I do if my pool shape does not match any standard cover?
If your pool has an irregular freeform shape, you have two practical choices depending on cover type. For a basic winter tarp, use the bounding box method and purchase a rectangular tarp that covers the widest and longest points with at least 4 feet of overlap. For a tensioned safety cover, you will need to map the pool perimeter using chalk marks and triangulation so a manufacturer can custom-cut the panels.
Why do safety cover makers ask for deck dimensions?
Safety covers rely on heavy brass anchors drilled directly into the deck around your pool perimeter. The manufacturer needs to verify that you have at least 3 feet of solid concrete decking on all sides so the tension springs have enough clearance to lay flat. If your deck is narrower or borders wooden decks, loose pavers, or grass, special hardware such as lawn stakes or wood deck anchors must be substituted.
Can I use a rectangular cover on an oval or freeform pool?
Yes, standard solid winter tarps and leaf nets can easily be rectangular on a curved pool. You simply order a rectangle large enough to cover the longest and widest points plus your required overlap. The excess fabric will rest on the deck where it can be weighted down with water tubes. However, tensioned safety mesh covers cannot use this shortcut and must be shaped to follow the pool contours.
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