How to Measure Your Pool for a Custom Cover

Modern Tarps

3 hours ago

6 min read

Key takeaways

To measure a pool for a cover, record length and width at the widest points, then add your chosen overhang before ordering.
Rectangular pools need only a few measurements, while freeform and Roman-end shapes require a grid of offsets from a straight baseline.
Always account for coping width, overhang and anchor point positions, or the finished cover will pull short or sag.
The most common measuring mistakes are guessing curves, ignoring coping, and measuring the water instead of the pool edge.
A professional measure-and-quote removes the guesswork and gives you a cover that fits the first time.

To measure your pool for a cover, record the length and width at the widest points from the outer edge, note the coping, and add your chosen overhang before you order. Curved pools need a few extra offset measurements, but the principle stays the same: measure the pool structure, not the water. Get those numbers right and a custom cover fits cleanly on the first fit.

A cover that fits well does real work. It keeps leaves and dirt out, slows evaporation, and adds a safety barrier over open water. Drowning is the leading cause of death for children ages 1 to 4, with about 4,000 fatal unintentional drownings each year in the United States (CDC, Drowning Facts, retrieved 2026-09-30). A properly sized cover is one layer of protection among several, and it only works if it actually fits the pool.

Tools You Need for an Accurate Pool Measurement

Getting an accurate measurement starts with the right kit. You do not need anything fancy, but guessing with a short household tape is where most bad fits begin. Gather everything before you start so you are not walking back and forth mid-measure.

Here is the basic list:

A long measuring tape, ideally 30 metres, or a laser distance measurer for straight runs.
A second person to hold the tape end and keep it taut.
Chalk, tape or pegs to mark reference points on the coping.
A notepad or phone to record every figure as you go.
A rough sketch of your pool shape drawn before you measure.

Draw the sketch first. Mark north, the position of steps, and any raised walls or spillways. Every measurement you take then has a clear home on the page. Trying to remember numbers without a diagram is how a 6-metre reading ends up recorded against the wrong edge.

Measuring Rectangular, Freeform and Roman-End Pools

Different pool shapes call for different measuring methods, and the shape decides how many readings you take. A rectangle needs a handful of numbers. A freeform pool needs a grid of them. Match your method to your shape and the cover maker gets a true picture of the surface.

Rectangular and square pools

Rectangular pools are the simplest. Measure the length along one long side, then the width across one short side, both at the widest point from outer edge to outer edge. Take a second reading on the opposite sides to confirm the pool is truly square. Older pools often drift a few centimetres out of true, and that difference matters for a tight cover.

Also measure both diagonals, corner to corner. If the two diagonals match, the pool is square. If they differ, note both, because your cover has to follow the real shape rather than an assumed one.

Freeform and kidney-shaped pools

Freeform pools need the offset method. Lay your tape in a straight line down the full length of the pool to create a baseline. At regular intervals along that baseline, say every 500mm, measure straight out at a right angle to the pool edge on both sides. Each of these offset readings maps a point on the curve.

The closer your intervals, the more accurately the cover follows the shape. Tight curves and narrow waists need more points than long, gentle sweeps. Record each offset with its position along the baseline so the pattern can be rebuilt exactly.

Roman-end pools

Roman-end pools combine straight sides with one or two curved, semicircular ends. Measure the straight section as you would a rectangle, then treat each curved end with the offset method above. Note where the straight run meets the curve, since that transition point controls how the cover drapes around the rounded end.

Accounting for Overhang, Coping and Anchor Points

A cover has to reach past the water and onto the surround, so your measurements must include more than the pool opening. Overhang, coping width and anchor positions all change the finished size. Skip them and even perfect edge measurements produce a cover that falls short.

Overhang is the extra material that extends beyond the pool edge, usually 150mm to 300mm depending on the cover type and how it fastens. This overlap is what lets the cover anchor and seal against debris. Confirm the overhang before ordering, because it gets added to every edge reading you took.

Coping is the capping around the pool rim. Measure its width, because covers that fix to the outside of the coping need those extra centimetres on every side. Then mark every anchor point: the deck fixings, straps or track positions. A cover sized for the water but not the anchors will sit wrong no matter how neat your numbers were.

Think of the full sequence as three layers: the pool edge, the coping, and the overhang out to the anchors. Measure each layer and note it separately. The cover maker then combines them rather than guessing where one stops and the next begins.

Common Measuring Mistakes That Ruin the Fit

Most poor-fitting covers trace back to a small handful of measuring errors, and every one is avoidable. Knowing them in advance is the easiest way to protect your order. A cover cut from wrong numbers cannot be stretched to fit later.

Watch for these:

Measuring the water, not the edge. The water sits below the coping, so a surface reading is always short. Measure the outer pool edge.
Guessing curves instead of taking offsets. Eyeballing a freeform shape never rebuilds the curve. Use the baseline-and-offset method every time.
Ignoring coping width. Forgetting the capping leaves the cover short on every side at once.
Forgetting the overhang. Recording only the opening produces a cover with no material to anchor.
A single reading per dimension. Pools drift out of square with age. Two readings per dimension, plus diagonals, catch the difference.
Not marking anchor points. Fixings that were never measured force awkward, uneven tension across the cover.

Measure twice and write everything down. If two readings of the same dimension disagree, measure a third time rather than averaging on the spot. Small errors compound across a large cover, and a 2-centimetre slip on each side becomes a visible gap once the cover is on.

A well-fitted cover also earns its keep beyond neatness. The US Department of Energy notes that covering a pool cuts evaporation and the energy needed to keep water warm, which is a real saving in the hot, dry conditions common across Gauteng and Limpopo (US Department of Energy, Energy Saver, retrieved 2026-09-30). None of that benefit lands if the cover leaves gaps.

Booking a Professional Measure-and-Quote

If your pool is anything other than a simple rectangle, a professional measure-and-quote is the surest route to a cover that fits first time. An experienced installer captures the shape, coping and anchor points in one visit and turns them straight into a pattern. It removes the guesswork that trips up most DIY measures.

Moderntarps offers a door-to-door measure-and-quote across Gauteng, Mpumalanga, North West and Limpopo, then manufactures the custom cover to those exact figures and installs it. Because the same team measures and fits, the numbers never get lost in translation between site and workshop. For safety covers specifically, professional measuring also matters for meeting recognised standards such as ASTM F1346, which sets out how a safety cover should perform over open water (ASTM International, F1346, retrieved 2026-09-30).

If you would rather measure yourself, do it methodically: sketch the pool, gather a long tape and a helper, and record edge, coping, overhang and anchor points as separate layers. Then double-check every figure before you order. Either way, the goal is the same: a cover cut to fit your actual pool. Book a measure or start your own sketch this week, while the pool is easy to reach and the season is on your side.

Frequently asked questions

How do I measure my pool for a custom cover?

Measure the length and width at the widest points from the outer pool edge, note the coping width, then add your chosen overhang. For curved pools, take offset measurements along a straight baseline to capture the shape.

Should I measure the water surface or the pool edge?

Measure the pool edge, not the water line. The water sits below the coping, so measuring the surface gives you a cover that is too small and leaves gaps around the perimeter.

How much overhang should a custom pool cover have?

A typical overhang is 150mm to 300mm beyond the pool edge, depending on the cover type and anchoring method. Your installer confirms the right allowance based on the coping and fixing points.

Can I measure a freeform or kidney-shaped pool myself?

Yes, but it takes care. Lay a straight baseline along the length, then measure perpendicular offsets to the pool edge at regular intervals. A booked professional measure is more reliable for complex curves.

Do I need to account for anchor points when measuring?

Yes. Anchor points, coping width and any raised features affect where the cover sits and how it fastens. Marking these before you measure prevents a cover that fits the water but not the surround.