A Practical Guide To Measuring Curtains & Blinds | How To

First things first

Before you pick up the tape measure

• Use a metal tape measure. Keep it straight and taut. A soft sewing tape can stretch or bend.
• Write down width first, then drop. Width is left to right; drop is the vertical length from the agreed starting point to the bottom.
• Use one unit throughout. Centimetres are convenient; record millimetre precision, for example 124.6cm. If an order form uses millimetres, 124.6cm = 1,246mm.
• Measure every window separately. Label them by room and position, even when they look identical.
• Measure twice. Have someone help with wide windows and use a suitable, stable step ladder where needed.
• Note anything in the way. Handles, tiles, radiators, deep sills, furniture and inward-opening windows can all affect the fit.

For made-to-measure orders, follow the measurement labels on the quote or order form. If these differ from a general guide, ask us which measurement is needed before submitting your final sizes.

01 · Curtains

How to measure for curtains

You need two main measurements: the width of your pole or track and your chosen curtain drop. Decide on your heading style first, because it affects where the drop begins.

Step 1. Position your pole or track

Ideally, fit your pole or track before taking final measurements. As a starting point, position it around 15cm above the window opening and extend it around 15–25cm beyond each side, where space allows. This gives the curtains room to sit beside the glass when open.

These are planning suggestions, not fixed rules. Thick, interlined or very wide curtains may need more stacking space. Check the position against the ceiling, adjacent walls and the projection of your sill or radiator. If the fittings are not installed yet, label your measurements as provisional.

Step 2. Measure the width

• Pole: measure between the decorative ends, called finials. Exclude the finials themselves.
• Track: measure the usable curtain-running length. For a track with overlapping sections, record each section and the overlap separately so the workroom can confirm the total coverage.
• Curved or bay track: measure along the track’s path, not a straight line across the bay. See the special-window advice below.

Step 3. Find the correct starting point for your drop

Step 4. Choose where the curtains finish

Step 5. Check the drop in three places

Measure at the left, centre and right from the same reference level. Keep all three readings. For curtains that must clear the floor or sill, work from the shortest reading and take off your chosen clearance once. If the difference is noticeable, send the readings and a photo before settling on a finished drop.

Finally, note any side returns, centre overlap or unusual brackets. These affect the making-up details and should be agreed separately from the basic pole width.

02 · Blinds

How to measure for Roman blinds

A recess is the opening in the wall that your window sits inside. First decide whether the blind will sit within this opening or on the wall above it.

Inside recess: measure the opening

1. Choose the fitting position. Check the specified headrail and bracket depth, allowing for handles, vents and opening windows. There is no single minimum depth for every blind.
2. Measure three widths: across the top, middle and bottom at the depth where the blind will hang. Include any tiles or trim that narrow its path.
3. Measure three drops: from the top of the recess to the sill at the left, centre and right.
4. Record every reading. Highlight the smallest width and smallest drop for a standard Roman blind, and label them “recess measurements — no deductions made”.
5. Confirm the order convention. Ask whether the workroom needs the recess size or the finished blind size. If it asks for recess size, do not subtract a fitting allowance yourself unless instructed.

Outside recess: measure the area to cover

1. Mark the top position. For a Roman blind, around 15–20cm above the opening can be a useful starting point. Ask about the raised stack depth: longer blinds and different fold styles may need more space to clear the glass.
2. Choose the side overlap. Around 5cm on each side is a starting point where space allows. Check adjacent walls, switches and trim.
3. Choose the bottom position. Around 5cm below the opening may suit a clear wall. A projecting sill or radiator may mean the blind needs to stop elsewhere or sit further forward.
4. Measure between your marks. Record the full width and the full top-to-bottom drop. Label these as the intended finished coverage, with overlaps included.

Overlap helps reduce edge gaps, but blackout fabric or lining does not guarantee a completely dark room: light can still enter around the blind.

Measuring for roller blinds and other systems

Roller fabric is narrower than the overall blind mechanism. Confirm whether the quoted width means bracket-to-bracket width or fabric width. For outside fitting, check that the actual fabric will cover the opening by your chosen amount.

For recess roller blinds, record the width at the bracket position as well as the narrowest width further down. Use the specific roller system’s measuring instructions to select the order size; do not automatically apply the Roman-blind rule to every product.

No-drill, Perfect Fit, Venetian, vertical, roof-window and motorised systems can have different measuring requirements. Identify the exact product before taking final order measurements.

Bay windows, doors & awkward spaces

• Bay windows: send a sketch with each section, the angles if known, and photographs. Adjacent blind headrails and projecting handles can clash at corners. Do not deduct a guessed amount or divide the whole bay into equal blinds.
• French or patio doors: check the opening arc, handle clearance and where curtains or raised blinds will sit when you use the doorway.
• Part-tiled recesses: record widths between the tiles as well as above them. The headrail must fit at the top and the fabric must pass through the narrowest part.
• Sloping floors or uneven openings: supply all readings and note the difference. Avoid averaging them into a size that may catch at the tightest point.
• Curtains and blinds together: check that the curtain pole projects far enough forward for both treatments to move freely.

If the shape is unusual, use your first measurements to start a conversation rather than as final cutting sizes.

03 · Choosing your fabric

How much fabric will you need?

Measuring the window is the first stage. The amount of fabric depends on the design as well as the finished dimensions, so a curtain drop of 2 metres does not necessarily mean you need 2 metres of fabric.

If you are making your own, use the allowances in your sewing pattern or blind-kit instructions. If we are making up your curtains or blinds, send us the measurements and your chosen fabric so the quantity can be confirmed for the design. Hem allowance can vary from project to project.

Explore our curtain fabrics or find out about our making-up service.

04 · Keep everything together

Your measurement record

Copy these fields into your notes or print this page. Use a separate record for each window; the blank cells are for your handwritten notes.

Before you request your quote

• I have measured each window twice and labelled the units.
• I have recorded the full pole / track width for curtains.
• I have stated exactly where the curtain drop starts and ends.
• I have identified recess measurements or intended finished blind coverage.
• I have clearly noted any clearance or overlap already included.
• I have checked handles, sills, opening windows and operating space.
• I have included photographs where the fit needs explaining.

Common measuring questions