How to measure your custom curtains: the complete guide for every window type

Why measurements are more important than fabric

A poorly sized curtain loses its performance, regardless of its fabric. Thermal and acoustic performance tests show that a curtain that is too narrow (without a lateral overhang of 15 cm) loses 30 to 40% of its insulation effectiveness. A curtain that is too short (5 cm above the floor) loses 20 to 30% of its ability to block cold and noise due to floor draft effect.

According to ADEME, windows account for 10 to 15% of a home's heat loss, which explains why a poorly sized curtain cancels out part of the expected gain.

In concrete terms: a high-performance thermal curtain (up to 7 °C, measured in the laboratory*) installed without lateral overhang lets cold air through at the sides. A 100% blackout curtain that is 5 cm too short will allow enough light to filter through to disturb sleep (5 to 10 lux). Measurement errors are the primary cause of disappointment after purchasing a custom curtain.

Summary table: how to measure according to your window

Universal rule: for technical curtains (thermal, blackout, soundproof), always take the largest measurement and round up to the nearest centimeter. A slightly too large curtain is easy to manage (hem, floor drop), a too small curtain cannot be fixed.

Classic window with existing rod

This is the most common case. You already have a rod installed above your window.

For the width: measure the rod from end cap to end cap (not the window, not the wall). Multiply this measurement by 2 to 2.5: this is the fullness Kurtens recommends. Example: a 120 cm rod gives a curtain 240 to 300 cm wide. If you order two panels, divide by two: 120 to 150 cm per panel. This flat width is what you enter in the configurator.

For the height: measure from the top of the rod (or the ring, depending on the type of attachment) to the floor. Add 2 to 5 cm for a drop that skims the floor. A curtain that stops 10 cm from the floor loses elegance and insulating performance (cold air draft from below).

For detailed measurement method adapted to Kurtens curtains (with automatic price calculation), consult our interactive size guide.

Window without rod: how to measure from scratch

No rod, no support. You must first decide where the rod will be positioned.

Rod position: 10 to 15 cm above the top of the window. The higher the rod, the more the curtain gives an impression of height to the room. For maximum effect, some install the rod just below the ceiling.

Width: measure the outer width of the window frame (not the glass, the entire frame). Add 30 cm (15 cm on each side): this gives the length of your future rod. Multiply it by 2 to 2.5 to get the total curtain width. Without this overhang, air circulates on the sides and thermal, acoustic, and blackout performance drops by 30 to 40%.

Height: measure from the planned rod location to the floor. Add 2 to 5 cm for the drop. If you choose eyelets, the top of the curtain extends approximately 2 to 3 cm above the rod: take this into account in your measurement.

Bay window: pitfalls to avoid

Bay windows are the most delicate surfaces to measure: often very wide (200 to 400 cm), sometimes asymmetrical, with walls that are not always perfectly parallel.

Essential rule: measure in three places. Width at the top, middle, and bottom. Height on the left, center, and right. Take the largest measurement in each direction. Discrepancies can be 1 to 3 cm, enough to create a visible gap if you take the wrong measurement.

For a bay over 200 cm, two panels that meet in the center are preferable to a single massive curtain. Each panel should overlap by 10 to 15 cm in the center when closed. Without this overlap, light, cold, and noise will pass through the middle.

270 cm is the width of the fabric roll, not an absolute maximum curtain height. The options depend on the combination of width and height. For dimensions not offered in the configurator, contact us to confirm production and whether a joining seam is needed. The configurator accepts any size up to 1,000 cm wide by 270 cm high, or up to 270 cm wide by 600 cm high; beyond that, contact our team for a quote.

Entrance door: measuring for insulation

A curtain in front of your entrance door helps reduce drafts. The width rule is the same as for a window. Take the opening of the door into account.

Width: measure the outer width of the door frame. Add 30 cm, i.e. 15 cm on each side, to get the length of the rod. Multiply this length by 2 to 2.5 to get the total curtain width. Check that the open curtain leaves the doorway completely clear.

Height: from the rod to the floor, with floor contact (1-2 cm excess). The space under the door is the main leakage point (up to 45 cm2 of opening on a standard 90 cm door with a 5 mm gap).

Rod projection: 10 to 15 cm from the wall so that the curtain does not obstruct the opening. Consult our article on what 30 dB attenuation means if your door has both thermal and sound problems.

Attic windows and atypical configurations

Roof windows (Velux type) and sloped windows pose a particular challenge. A curtain held only at the top pulls away from the glass on a sloped window: it also has to be held at the bottom.

Two solutions exist:

• Direct installation on the frame: curtain held by a fixing at the top and one at the bottom, or blind with side guides. In both cases, measure the width and the height of the inner frame of the roof window. For the curtain, the rod pocket is the recommended heading.
• Rod at the base of the slope: placed where the wall meets the sloped ceiling, the curtain hangs vertically and covers the entire sloped surface. Measure the wall width and the height from the floor to the wall/ceiling junction point.

For arched, corner, or curved bay windows: measure the total width in a straight line (not following the curve) and the maximum height. The curtain will hang straight in front of the glazed surface. For any atypical configuration, contact our team with your measurements and a photo.

The 5 most common measurement errors

• Error 1: measuring the window instead of the rod. The width of the curtain should match the rod, not the glass. The rod always extends 15 cm beyond the window on each side.
• Error 2: forgetting the fullness coefficient. A flat curtain without pleats loses aesthetic appeal and insulating performance (no air pocket between the folds). Multiply the rod width by 2 to 2.5.
• Error 3: measuring from the ceiling instead of the rod. The curtain starts at the rod, not the ceiling. If the rod is 10 cm from the ceiling, these 10 cm are not part of the curtain height.
• Error 4: ignoring the type of attachment. An eyelet curtain extends 2 to 3 cm above the rod. A pencil pleat curtain starts directly below the hooks. The visible height varies. Consult our attachment guide.
• Error 5: taking only one measurement. Walls are not always square, and floors are not always level. Measure the height on the left and right, and the width at the top and bottom. Always take the largest measurement. Common deviation: 1 to 3 cm.

Standard size or custom-made: how to decide

Custom-made is recommended whenever technical performance matters: total blackout and thermal insulation directly depend on full window coverage. If no standard size matches, the Kurtens customizer allows you to enter your exact dimensions and see the price instantly.

*Data from tests conducted under optimal conditions.

Comparing with a standard-size curtain, from IKEA for example? Read Does IKEA make made-to-measure curtains?.

Need to close off a wardrobe or storage space under the eaves? Read Sloped ceiling curtain: close off your wardrobe made to measure.

How do I measure a window for curtains?

Choose the heading first. Width is measured on the rod, between its end caps, or on the outer frame plus 15 cm on each side, then multiplied by 2 to 2.5. The drop is measured from the reference point of the heading to the desired hem line.

Measure the drop in several places, as floors are not always level. This reference point depends on the heading: eyelets make the top of the curtain rise above the rod; with pencil pleat tape, the position of the top edge depends on how the hooks are set in the tape. In front of a door, check that the rod's distance from the wall, 10 to 15 cm, and the open curtain let the door open fully. If in doubt about the dimensions to order, have them confirmed by our team.

What curtain width should I choose for my window?

Take the length of the rod, which extends 15 cm beyond the frame on each side, and multiply it by 2 to 2.5: 2 for full folds, 2.5 for fuller folds. When open, the curtain stacks partly on this overhang; how much space it takes depends on its thickness and fullness.

For two panels, divide this width by two. Example: a 230 cm rod gives 460 to 575 cm of curtain, or two panels of 230 to 288 cm. In the configurator, you enter the flat width of one panel.

How do I measure curtains for a curtain pole or a track?

Measure the length of the pole or track and multiply it by 2 to 2.5. Measure the drop from the pole, or from the hook point of the track gliders, to the desired hem line, then adjust it to the heading. When open, the curtain takes up part of the side overhang, depending on its thickness.

The heading follows the support. Eyelets or a rod pocket slide onto a pole. On a track, the curtain hangs from the gliders on hooks, with pencil pleat tape: the position of its top edge depends on how the hooks are set in the tape, to be checked before setting the drop. Our heading guide compares the options. Kurtens sells neither poles nor tracks: measure the one you already have or plan to fit.

With eyelet curtains, what drop should I order and how far are the eyelets from the top?

Measure from the top of the pole to the floor, then add about 2 to 3 cm: with eyelets, the top of the curtain sits that much above the pole. Without this addition, the hem ends up that much higher than intended. The total is an estimate for a curtain that just skims the floor.

Then adjust for the finish: for a curtain that pools on the floor, add the fabric meant to rest on it; for a curtain that stops above the floor, subtract the gap you want. Kurtens eyelets measure 40 mm: check that your pole fits through them. Before setting the drop, ask our team to confirm how far the curtain rises above the pole and the distance between the eyelets and the top of the curtain for the chosen make-up.

What curtain size should I order if the rod is on the ceiling and the window is in a recess?

Fixed to the ceiling in front of the recess, the rod extends 15 cm beyond the opening on each side; inside the recess, it runs wall to wall. Either way, order its length times 2 to 2.5, and a drop from the heading's reference point to the desired hem line, adjusted for the position of the top edge.

In front of the recess, the curtain covers the opening and its sides: this is the set-up to favour for a blackout, thermal or acoustic curtain. Measure from the rod, not from the ceiling, and leave a gap between the two if you choose eyelets, since the top of the curtain rises above the rod.

Inside the recess, check that the curtain does not get in the way when the window opens, and measure the drop on the left, in the centre and on the right: if the curtain must stop above the sill, start from the smallest and subtract the clearance you want. Drops under 150 cm can also be ordered in the configurator: the curtain is made to the exact measurement, at the price of the smallest listed size that covers it.

How do I measure curtains for a bay window?

Measure the track or pole that follows the bay with a flexible tape measure, along its whole path, angles or curve included, then multiply this length by 2 to 2.5. Plan several panels, spread across the sections where they can slide. Measure the drop under each section, from the reference point of the heading to the desired hem line.

Set the drop of each panel according to the section it covers; only use a common drop if it works along the whole length. Another, simpler option: a straight rod across the opening of the bay. The curtain then closes off the whole bay, as in front of a large glazed window: measure the outer width of the bay in a straight line. Add 30 cm to get the length of the future rod, then multiply it by 2 to 2.5 to get the total curtain width.

Kurtens sells neither poles nor tracks; a bendable track is available from a specialist, and what counts is its length once fitted. For a size the configurator does not offer, send your measurements and a photo to our team.

Where can I get custom curtains for an irregular window?

From a made-to-measure curtain maker such as Kurtens. For an arched, curved or angled window, the simplest solution is a rectangular curtain on a straight rod fitted above it, sized from that rod: overhangs, fullness, desired hem line. It falls in front of the whole glazed area. For other shapes, send measurements and a photo to check feasibility.

Measure the total width in a straight line, without following the curve, to set the rod length with its overhang, then apply fullness. Measure the drop from the reference point of the heading to the hem line you want. The configurator offers rectangular curtains in any size up to 1,000 cm wide by 270 cm high, or 270 cm wide by 600 cm high, including drops under 150 cm; any other request goes through the contact page. For storage or a nook under the eaves, also read Sloped ceiling curtain: close off your wardrobe made to measure.

Is it worth getting curtains made to measure?

Yes, as soon as no standard size covers your window with its overhangs and the drop you want. If a standard size matches the curtain width and drop your set-up needs, it is enough. Made to measure matters most for a blackout, thermal or acoustic curtain, whose performance depends on that coverage.

Made to measure sets the dimensions, the range sets the function: then choose the fabric for what you expect, blocking light, insulating or filtering it. Against a measuring error, the optional Exact-Fit Guarantee lets you request a free remake to the right dimensions within 30 days of receipt. The made-to-measure configurator shows the price as soon as you enter your dimensions.

Frequently Asked Questions