To measure for a pool cover, measure the pool opening or waterline dimensions that the cover manufacturer asks for, not the size of the surrounding deck and not automatically the size of an old cover. For a simple rectangle, record the length and width and check the diagonals. For a round pool, measure the diameter at the widest point. For an oval, record the overall length and width. Steps, spas, raised walls, rails, waterfalls, and irregular curves may require extra measurements.
The exact method depends on the cover. A solar blanket can often be sized from straightforward length-and-width measurements and then trimmed to fit. A stock winter cover is normally ordered by the pool’s stated size, with the manufacturer providing the required overlap. A custom safety cover is much more precise and may require an A-B triangulation survey, a pool sketch, deck information, photos, and measurements of existing anchors or obstructions.
Start by Identifying the Type of Pool Cover
The phrase “pool cover” includes several products that are measured differently. Before using a tape measure, identify whether you are ordering a solar cover, a basic winter or debris cover, a fitted above-ground cover, a custom safety cover, or a replacement safety cover that must work with existing anchors.
| Cover type | Measurements normally needed | Important extra check |
|---|---|---|
| Solar or bubble cover | Pool length and width; step area separately if it extends beyond the main body | Confirm whether the cover will be supplied oversized for trimming or pre-cut to the waterline |
| Standard winter or debris cover | Nominal pool length and width, or diameter for a round pool | Use the maker’s size chart because overlap is often already included in the finished cover |
| Stock safety cover for a standard shape | Inside pool dimensions, shape, step dimensions and location, plus checks for deck and obstructions | Existing anchors usually require a replacement or custom measurement process rather than a new stock layout |
| Custom or freeform safety cover | Detailed perimeter points, A-B distances, overall cross-check dimensions, deck features and obstructions | Use the exact manufacturer measuring form and point order; professional measuring may be required |
This distinction matters because a number printed on a cover package may describe the pool it is intended to fit rather than the physical dimensions of the cover itself. Safety covers in particular are manufactured larger than the water opening so they can overlap the pool edge and connect to anchors on the deck. Measuring the finished cover instead of the pool can therefore produce the wrong order.
Tools You Need to Measure a Pool Accurately
A basic pool can be measured with a good tape and a notebook. A custom pool needs a more organised setup because one misplaced point can change the reconstructed shape.
- A long, non-stretch measuring tape suitable for the size of the pool
- Chalk or removable painter’s tape for marking reference points
- A notebook, printed measuring form, or graph paper
- A pencil or waterproof marker
- A helper for long measurements and diagonals
- A phone or camera for recording steps, raised walls, rails, rocks, spas, and other features
- The cover manufacturer’s measuring sheet when ordering a custom or replacement cover
Record measurements as you take them rather than relying on memory. Use one unit system consistently throughout a custom measuring form. If the form asks for feet and inches, write both clearly. If it asks for millimetres, do not mix centimetres and millimetres in different rows.
How to Measure a Rectangular or Square Pool
A true rectangle is the easiest pool to measure, but length and width alone do not always prove that the pool is square. Older pools, hand-formed shells, coping changes, and renovations can introduce small differences between one side and the other.
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Identify the measuring edge
Use the waterline, inside edge of coping, or other reference specified by the cover manufacturer. Keep that same reference around the entire pool.
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Measure the full length
Measure from one inside end of the pool to the opposite inside end. If accuracy is important for a safety cover, also measure the length along the other side and note any difference.
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Measure the full width
Measure across the pool at the inside edges. On a pool that may not be perfectly uniform, take width measurements near both ends and through the middle.
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Check both diagonals
Measure corner to opposite corner in both directions. Similar diagonal measurements support that the pool is square; a meaningful difference tells you not to assume a perfect stock rectangle.
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Measure steps and projecting features separately
If a step, tanning ledge, bench, or spa extends outside the main rectangle, record its width, projection, position, and any curved or angled edges required by the cover form.
For a simple solar blanket, a manufacturer may need only the longest length and width because the material is supplied slightly oversized and trimmed on the pool. Daisy Pool Covers’ solar-cover sizing guidance, for example, instructs customers to measure pool length and width and to measure step areas separately; uniquely shaped pools can be treated as a rectangle when the cover is being supplied oversized for trimming.
A custom safety cover is less forgiving. It may require exact inside dimensions, diagonals, step geometry, deck measurements, and obstacle locations. If the diagonals disagree or the sides are not equal, record the actual measurements rather than forcing the pool into a theoretical rectangle.
How to Measure a Round Pool
For a round pool, measure the diameter from one inside edge to the opposite inside edge through the centre. Do not measure around the circumference unless the sizing instructions specifically request it. Pool covers for standard round above-ground pools are usually selected by diameter.
It is useful to check the diameter in at least two directions if the pool is older or if the wall does not look perfectly circular. A significant difference can indicate that the pool is out of round or that you are not measuring through the true centre. For a basic winter cover, use the manufacturer’s size chart once you know the actual pool diameter.
Do not add overlap to the diameter on your own unless the instructions tell you to. A cover sold for a particular round-pool size is commonly manufactured larger than the stated pool diameter so it can extend down or beyond the pool edge. The amount of extra material varies by product.
How to Measure an Oval Pool
For a standard oval, record the overall inside length from end to end and the overall inside width at the widest point. Take the width through the centre rather than measuring one of the narrower curved sections near an end.
Above-ground oval pools can also have external buttresses or support structures. Those frame parts may matter for a fitted cover or tie-down system even though they are not part of the water opening. Check whether the product’s sizing chart is based on nominal pool size, inside wall dimensions, or outside frame dimensions before ordering.
For an inground oval that will receive a custom safety cover, the overall length and width are useful cross-checks but may not be enough by themselves. The exact perimeter shape may still need a custom point survey so the finished cover follows the curve correctly.
How to Measure Steps, Ledges, Spas, and Other Extensions
Features that extend beyond the main pool body are a common source of ordering errors. Measure them as separate geometry rather than simply adding their projection to the total pool length. A manufacturer needs to know where the feature begins and ends as well as how far it extends.
External steps
Record the step section’s width along the pool wall and its projection away from the main pool body. Also record its location. For a rectangular pool, note whether it is centred, offset to one side, or flush with a corner. If the manufacturer provides a diagram showing the viewing direction for “left” and “right,” follow that diagram exactly rather than using your own viewpoint.
Tanning ledges and benches
A ledge that remains inside the main waterline rectangle may not change the outer cover shape, but a ledge that projects beyond the normal perimeter does. Sketch its outline and measure the dimensions that change the waterline boundary.
Attached spas
An attached spa can create extra curves, raised walls, spillways, or changes in deck height. Those features often push a safety-cover order into a custom measurement process. Record where the spa meets the pool and include photographs showing the wall heights and the intended cover attachment area.
Rails, ladders, slides, waterfalls, rocks, and raised walls
These features may affect where straps and anchors can run. The current LOOP-LOC measuring form directs measurers to show deck areas, planters, and obstructions near the waterline and to mark items such as ladders, handrails, slide legs, rocks, spillways, spa walls, and raised areas when creating a custom survey. That is a useful reminder that a cover is fitted to the whole installation, not just the blue water shape.
How the A-B Measurement Method Works for Freeform Pools
Freeform, kidney, lagoon, and heavily modified pools cannot always be described accurately with one length and one width. Custom cover manufacturers therefore use triangulation. Two fixed reference points, called A and B, are established outside the pool, and each marked point on the pool perimeter is measured from both A and B.
Those paired distances allow the cover designer to reconstruct the location of each perimeter point. The method is conceptually simple, but accuracy depends on keeping A and B fixed, numbering perimeter points consistently, measuring to the exact same edge every time, and recording every distance correctly.
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Draw a clear pool sketch
Show the pool shape, deck, steps, attached spa, raised walls, planters, rails, waterfalls, rocks, and any other feature that can affect the cover or its anchors.
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Establish fixed points A and B
Position the baseline exactly as the cover manufacturer’s measuring form requires. For LOOP-LOC’s current measuring instructions, the baseline is placed outside the pool, kept from crossing the pool outline, and sized in relation to the pool length.
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Mark numbered points around the perimeter
Place points along the chosen inside pool edge. Use closer spacing through tight curves and mark every corner, transition, obstruction, or feature identified by the manufacturer’s form.
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Measure from A to every numbered point
Keep the A reference point fixed and record the distance from A to point 1, point 2, point 3, and so on around the pool.
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Measure from B to the same points
Repeat the process from B without changing any perimeter marks. Every numbered perimeter point should have both an A distance and a B distance.
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Add independent cross-check measurements
Record overall length, overall width, step dimensions, and other known distances requested by the form. These checks can reveal a recording error before a custom cover is manufactured.
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Submit the sketch and photos with the measurements
Show unusual features clearly. Custom safety-cover manufacturers may require photos or professional review before accepting the measurements.
LOOP-LOC’s measuring instructions call for numbered perimeter points at approximately 3-foot intervals, with closer 1- to 2-foot spacing in small or tight-radius areas. Those figures are specific to that manufacturer’s process, so they should not be copied blindly to another brand. Use the form supplied with the cover you intend to order.
A similar two-reference-point method also appears in Daisy Pool Covers’ pre-cut curvilinear-cover measuring form. Its form has the measurer mark points around the pool and record distances from both reference points to each perimeter point, demonstrating why complex shapes need more than a simple length-and-width measurement.
How to Measure for a Solar Pool Cover
Solar covers are usually the least complicated to size because the material floats on the water and does not need deck anchors. For a rectangular pool, measure the water surface length and width. If steps project beyond the main body, measure the step section separately. For a round pool, record the diameter; for an oval, record the maximum length and width.
Many solar covers are intentionally supplied slightly oversized so they can be trimmed on site. Daisy states that its standard solar covers are supplied oversized for trimming, while its pre-cut service can use waterline measurements or a small upturn depending on the selected fit. This is why you should not add your own allowance until you know how the manufacturer prepares the cover.
If you plan to use a roller, also think about the roller direction. A pool with a wide step section may need the step portion folded onto the main cover during rolling or may require a separate piece. The pool-cover supplier can advise whether the roller should span only the main body or include the step width.
How to Measure for a Standard Winter or Above-Ground Pool Cover
For a standard winter cover, start with the actual pool size: diameter for a round pool, length and width for an oval or rectangle. Then match that measurement to the manufacturer’s sizing chart. The finished cover may be larger than the pool size shown on the label because it needs overlap for securing around the wall or deck.
Do not measure from one outside support leg to another unless the cover instructions specifically define the size that way. On portable frame pools, the widest external frame dimension can be larger than the water opening, while the fitted cover may be designed around the rim. The correct reference is whatever the product’s size chart specifies.
If your pool is a non-standard oval, has an attached deck, unusual top rails, or permanent obstructions, confirm fit before ordering. A cover that nominally matches the water dimensions can still interfere with railing posts, ladders, or deck structures.
Measuring for a Safety Cover Is Different
A safety cover is part of an anchored system, so fit involves the pool opening, cover overlap, straps, springs, anchors, deck material, and nearby structures. This is why custom safety-cover measurements are more demanding than solar-blanket measurements.
LOOP-LOC describes its safety covers as custom fitted using computer-aided design, and its published guidance emphasises measuring steps, ladders, handrails, spas, waterfalls, and other special features. The manufacturer also recommends professional measuring and installation for form-fit pools. That is sensible because an incorrect measurement can affect where the finished cover lands relative to the deck and anchors.
If your pool is a simple standard rectangle and you are considering a stock safety cover, confirm that the stock shape truly matches the pool. Measure both lengths, both widths, the diagonals, the step, and the available deck. A pool that appears rectangular can still be out of square enough to make a custom cover the better fit.
How to Measure for a Replacement Safety Cover
Replacement safety covers deserve special attention because the existing deck anchors may need to be reused. In that situation, measuring only the pool opening is not always enough. The new strap layout must correspond to the anchor pattern, or the deck may require new anchor locations.
First check whether the old cover has a manufacturer label, serial number, order number, or other identifying information. Some manufacturers can reproduce a cover from their original records, which may be more reliable than starting from zero.
If the original record cannot be used, the replacement measuring form may ask for A-B measurements to both the pool perimeter and the existing anchors. LOOP-LOC’s current measuring instructions specifically describe a replacement process in which the A-B baseline is related to the anchor locations and, where possible, the same baseline is used for both the pool and the anchors.
Do not simply measure the old fabric after years of use and assume those dimensions define the replacement. Fabric can stretch, shrink, wear, or sit differently under tension. A manufacturer-approved replacement survey is the safer way to preserve an existing anchor layout.
Common Pool-Cover Measuring Mistakes
Measuring the old cover instead of the pool
The old cover may include built-in overlap and may have changed shape with age. Unless the manufacturer specifically asks for finished-cover dimensions, measure the pool or use the replacement-cover procedure.
Adding extra overlap without checking the size chart
This can result in ordering a cover that is much too large. Start with the actual pool measurements and let the manufacturer’s product dimensions or custom design provide the required overlap.
Ignoring steps and other projections
A main rectangle measurement does not describe a projecting stair section or spa. Record the feature’s position, width, projection, and shape using the cover maker’s diagram.
Assuming a rectangle is perfectly square
Check both diagonals and, for precise orders, both sides and multiple widths. If the values disagree, record what the pool actually measures rather than averaging everything into a theoretical rectangle.
Moving the A or B reference point halfway through
A-B triangulation depends on fixed reference points. If either point moves, the later measurements no longer describe the same coordinate system. Mark the points clearly and leave them unchanged until every dimension has been checked.
Numbering custom perimeter points in the wrong order
The point sequence matters. Daisy’s curvilinear measuring form, for example, explicitly warns that reversing the direction can produce an inverted result. Follow the direction and numbering convention printed on the manufacturer form.
Forgetting the deck and anchor area
A safety cover needs somewhere for its hardware to go. Measure or document narrow deck sections, raised walls, planters, pavers, wood decking, rocks, waterfalls, and other conditions that can affect anchor placement. A perfect pool outline is not enough if the cover cannot be anchored as designed.
How to Double-Check Your Measurements Before Ordering
Rechecking takes less time than correcting a custom order. Before submitting the measurements, compare the written numbers with the sketch and make sure the shape they describe makes sense.
- Re-measure the longest length and widest width.
- Check both diagonals on rectangular pools.
- Confirm that every projecting step or spa has its own dimensions.
- Verify that A and B did not move during a custom survey.
- Make sure every numbered perimeter point has both an A and a B value.
- Check that feet, inches, centimetres, or millimetres are used consistently.
- Compare the pool sketch with current photos.
- Show all obstructions and changes in deck level requested by the manufacturer.
- For a replacement safety cover, include existing anchor information if the new cover must reuse them.
If one number looks inconsistent, re-measure it instead of trying to “correct” it mathematically. Pools can be slightly out of square, curved sections may not be symmetrical, and renovation work can create real differences that a custom cover needs to reproduce.
Frequently Asked Questions
Do I measure the pool or the old cover?
Measure the pool unless the replacement-cover instructions specifically ask for the old cover or existing anchor dimensions. Stock covers are generally sized to the pool, while custom replacement safety covers may use original serial information or a detailed anchor survey.
Should I add extra inches for overlap?
Not automatically. Many covers already include the required overlap in the manufactured size. Record the true pool dimensions first and follow the sizing chart or custom measurement form for the specific cover.
Where do I measure a pool from?
Use the reference specified by the manufacturer, commonly the inside pool edge or waterline for custom covers. The important part is consistency: do not measure one side from the coping edge and another from the outside deck edge.
How do I measure a pool with steps?
Measure the main pool body first, then measure the step section separately. Record its width, how far it projects beyond the main wall, its position, and any curved or angled edges requested on the cover diagram.
Can I measure a kidney-shaped pool with only length and width?
Length and width may be enough for an oversized solar cover that will be trimmed on site, but they are generally not enough for a custom safety cover. A freeform safety cover normally needs a detailed point survey such as the manufacturer’s A-B triangulation method.
Do existing safety-cover anchors need to be measured?
They may need to be if the replacement cover must reuse them. Check whether the original cover can be identified from a serial or order number first. If not, use the manufacturer’s replacement measuring procedure rather than assuming a new stock cover will line up with old anchors.
Measure the Pool First, Then Apply the Cover Maker’s Rules
The safest way to measure for a pool cover is to separate the actual pool dimensions from the allowance built into the cover. Measure the water opening or inside edge consistently, record the true shape, measure steps and extensions separately, and document anything that may affect fit or anchors.
For a standard round, oval, or rectangular cover, those measurements can often be matched directly to a manufacturer’s size chart. For solar covers, the material may be supplied oversized and trimmed. For custom safety covers, use the exact measuring form, keep reference points fixed, document the deck and obstructions, and have the measurements reviewed professionally when the manufacturer requires it. Accurate measuring is less about adding generous extra material and more about describing the pool exactly as it exists.
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