Pool Liner Size Calculator

How the pool liner calculator works

This calculator sizes a single flat sheet of liner that covers the floor of a rectangular pool, runs up all four walls and laps over the edge. Add twice the depth and twice the overlap to both the length and the width, then multiply the two. Twice the depth, because the sheet goes down one wall and back up the other; twice the overlap, because there's an edge on each side.

With the US defaults, a pool 26 ft by 13 ft and 5 ft deep with 1 ft of overlap needs a sheet 26 + 10 + 2 = 38 ft long and 13 + 10 + 2 = 25 ft wide: 950 ft², or $2,185 at $2.30 per ft². The metric default, 8 m by 4 m and 1.5 m deep with 0.3 m of overlap, needs 11.6 m by 7.6 m, which is 88.16 m² and £2,204 at £25 per m².

Where the formula comes from

It's the standard rule for one-piece membrane liners such as EPDM or PVC, and liner suppliers publish it in the same form. Russell Water Gardens, for example, gives liner length as length plus twice the depth plus a 2 ft safety overlap, and the same for width. Its guide says to measure the longest length, the widest width and the deepest depth, and allow 1 ft of overlap on each side. Its worked example is a pond 17 ft by 12 ft and 2 ft deep, which needs 23 ft by 18 ft of liner; because that supplier sells liner in 5 ft steps, the order becomes 25 ft by 20 ft.

Always use the deepest point. If the floor slopes from 3 ft at one end to 8 ft at the other, size for 8 ft. The sheet is then generous at the shallow end, but a sheet that's short at the deep end can't be fixed.

Two more worked examples

A small garden pond 3 m by 2 m and 0.8 m deep, with 0.3 m of overlap, needs a sheet 3 + 1.6 + 0.6 = 5.2 m by 2 + 1.6 + 0.6 = 4.2 m, or 21.84 m², to line 14 m² of floor and wall. A pool 32 ft by 16 ft whose floor falls from 3 ft to 8 ft is sized on the 8 ft depth: 50 ft by 34 ft, 1,700 ft². Its surface-to-line figure of 1,280 ft² treats every wall as 8 ft deep, so for a sloping floor it's an upper limit, not the true fitted area.

The sheet is bigger than the surface it covers

A flat sheet has to fold at each corner, so some of it never touches the pool. The result card shows the surface actually being lined, the floor plus the four walls: 26 × 13 + 2 × 5 × (26 + 13) = 728 ft² for the US default, against a 950 ft² sheet. Of the 222 ft² difference, 4 × 5 × 5 = 100 ft² sits in the four corner folds and 122 ft² is the overlap round the edge. In metric, 68 m² of surface takes an 88.16 m² sheet: 9 m² in the corners and about 11.2 m² of overlap.

That gap matters when you price the job. A supplier quoting per square metre of sheet is pricing the whole sheet, folds and all, which is why the calculator costs the sheet area rather than the surface.

Custom vinyl pool liners are ordered differently

Most in-ground vinyl pool liners aren't cut from a flat sheet on site. They're made to measure for the exact shape of the pool and clip into a track under the coping. Manufacturers design them from a measuring form. Findlay Vinyl's measuring guide tells owners to measure the actual pool rather than rely on the original plans, never to assume the pool is standard, and not to add anything for shrinkage or expansion, because the maker allows for that when the liner is designed. Johnson Products' guide shows the measurements involved: overall length and width, the shallow-end depth up to where the liner clips into the coping, the deep-end depth and the position of the slopes.

For a custom vinyl liner, use this calculator as a rough check on the amount of material and the price range, then order from the maker's form. The surface-to-line figure is the closer guide to what a fitted liner covers.

Choosing the overlap

The overlap is the flap that's buried, weighted down or fixed at the edge. The 1 ft (0.3 m) default matches the supplier guidance above; allow more where the edge detail is complicated or the ground is uneven, and check what your edging or fixing system needs. For a sheet liner, round the result up to the next size the supplier sells, since sheets usually come in set widths and lengths.