Bay Windows

Wallpaper for a Bay Window: Measuring a Curved or Angled Bay

Updated: Aug 2026

A bay window breaks what would otherwise be one flat wall into several angled panes — sometimes three, sometimes five, occasionally a continuous curve on an older bow window. A standard "width × height" calculator wants a single flat wall to work from, and a bay simply doesn't offer one. Here's what actually changes when a wall isn't flat, and how to still measure a bay properly instead of flattening it into a number that doesn't match what's on the wall.

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Measure each pane as its own short wall

Every flat pane of a bay — the two or four angled sides plus the central face — gets its own width and height measurement, the same as any other wall in the room. The angle between panes doesn't matter for wallpaper purposes: strips hang straight down regardless of how the wall next to them is angled, so there's nothing special to calculate about the angle itself, only about treating each pane separately rather than trying to sum them into one flat total.

The window recess splits panes into sections above and below the sill

Most bay windows have a sill or sub-sill running across some or all of the panes, with a shorter run of wall below it and a taller run above and beside the glass. Measure the wall above the sill and any wall below it as separate short sections on each pane, rather than treating the whole pane height as one continuous strip run interrupted by glass.

A curved bow window needs narrower, more frequent strips

Older bow windows are often genuinely curved rather than angled in flat panes, and a flat strip of wallpaper can only hug a curve if it's narrow enough that the small flat facet it creates isn't visible. That means more, narrower strips and more seams than the same width of flat wall would need — plan for a higher strip count on a curved bay, not the same count as an equivalent flat run.

Corners inside a bay are tighter than a standard room corner

The internal angles where a bay's panes meet are usually less than the 90° corners the rest of the room has, which makes pattern matching across them noticeably harder — a strip that lines up cleanly on a square corner can visibly step out of alignment on a bay's shallower angle. If the pattern needs to read as continuous around the bay, plan which strip starts at which corner deliberately rather than papering pane by pane and hoping it lines up.

Order a buffer roll for the extra seams

Splitting one wall's worth of width into several short panes means more seams and more offcut per metre than the same width papered as a single flat wall would produce. A bay window is exactly the kind of job where the seam count, not the total area, is what drives the waste up — order a buffer roll the same way you would for any wall with an unusually high number of short strips.

Worked example: a five-pane square bay

A square bay with two 40 cm angled returns, two 70 cm side panes, and a 1.2 m central pane, all 2.3 m to the picture rail, totals about 5.4 m of width across five panes. On a 53 cm roll, that's 11 strips — but because each pane needs at least one full strip (a pane can't share a part-strip with its neighbour across an internal angle), a 40 cm return still consumes a full 53 cm strip. The five-pane split needs 11 strips against roughly 10 for the same total width on one flat wall — the extra strip is the corner cost of a bay.

Radiators under a bay window — measure the wall below the sill separately

Bay windows very often have a radiator fitted below the window, sitting in the shorter run of wall beneath the sill. If the radiator is shallow, wallpaper still runs behind it as normal wall. If you're papering below a deep radiator you plan to remove and refit, treat that run as its own short section with its own height, since it won't share a strip with the taller wall above the sill. For more on handling reveals and returns around windows, see wallpapering around windows and corners

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Common questions

Is a bay window wall measured differently from the flat walls around it?

Each pane of the bay is measured as its own short wall, the same approach as an alcove's return walls or a hallway's individual straight runs — you're not measuring the bay as one number, you're measuring several small ones.

Do curved bay windows need a different type of wallpaper?

Not necessarily a different product, but a thinner, more flexible paper generally hugs a curve better than a stiff vinyl, which can crack or lift at the tightest part of the curve — check your supplier's guidance for curved or bowed walls before ordering.

Can the planner handle a bay window directly?

There's no single named bay-window template, but the room editor's free-form point-by-point outline handles any number of angled or curved panes — draw each pane as its own short wall the same way you'd sketch it on a floor plan.

Does a bay window need more wallpaper than a flat wall of the same width?

Slightly more, yes. Splitting one width into several panes means each pane rounds up to its own whole strip at the internal corners, rather than one continuous run across a flat wall — so a bay typically uses one or two more strips than the same total width on a flat wall.

How do I measure a bay window with a curved sill?

Measure the wall height and pane widths the same as a flat bay — the sill's curve affects the window, not the wall above and beside it. Treat each section above and below the sill on every pane as its own short measurement.