How to Measure Windows for Curtains and Blinds

What you need

• A steel tape measure (not a cloth tape)
• A pencil, paper or phone notes
• A ladder if the windows are high

Step 1: Decide inside or outside fit (for blinds)

Inside fit sits within the window frame and looks neat. It needs a frame deep and square enough to hold the blind. Outside fit sits on the wall or ceiling above the frame. It hides gaps and blocks more light around the edges.

Step 2: Measure width

1. For an inside fit, measure the width at the top, middle and bottom of the frame.
2. Write down the smallest of the three. Frames are often not perfectly square.
3. For an outside fit, measure the width you want to cover, usually the frame plus a few centimetres on each side.

Step 3: Measure height

1. For an inside fit, measure the height on the left, middle and right.
2. For an outside fit, measure from where the blind will be fixed to the sill or the bottom you want.
3. Note anything in the way, such as handles, locks or AC pipes.

Step 4: Measure for curtains

• Width: measure the length of the rod or track. Curtains need extra fabric to form folds, so the finished fabric is wider than the track.
• Height: measure from the rod or track to where you want the curtain to end. Choices are just below the sill, just below the sill and apron, or close to the floor.
• Take the measurement at more than one place, since floors may not be level.

Step 5: Write it down properly

For each window note the room, the width, the height, inside or outside fit, and the unit (inches, feet or centimetres). A photo of each window helps.

Common mistakes

• Using a cloth tape that stretches
• Measuring once instead of three times
• Forgetting handles, grills and AC pipes
• Mixing up width and height, or feet and inches
• Ordering before checking fabric samples in your own light

Prefer not to measure?

Blinds that are even slightly wrong can leave gaps or jam. Our team measures every window during a free site visit and brings fabric samples. Read how different blinds compare in our guide to zebra and roller blinds.

A simple worked example

Suppose your bedroom window frame measures 1,200 mm wide at the top, 1,195 mm in the middle and 1,198 mm at the bottom, and 1,500 mm high at all three places. For an inside-fit blind you would note the width as the smallest figure, 1,195 mm, and the height as 1,500 mm. For curtains you would measure the rod or track you intend to fit rather than the glass itself, and decide where the curtain should end.

Curtain styles and what they need

• Eyelet curtains: a clean, modern fold that slides on a rod.
• Pinch-pleat curtains: a formal look on a track or rod; they need more fabric width.
• Sheer curtains: a light layer that softens daylight; often paired with a heavier curtain.
• Blackout curtains: a lined layer for bedrooms; the lining adds weight, so the rod or track must be strong.

Checklist for your site visit

1. Clear the area around the windows so they can be measured.
2. Decide which rooms need privacy, blackout or glare control.
3. Have a rough idea of your budget range and preferred colours.
4. Note any AC units, grills or other fittings near the windows.
5. Keep photographs of the room or furniture that you want the fabric to match.

What affects the quotation

For curtains and blinds the price depends on the number of windows, their sizes, the fabric, the style and lining, the rod or track, any motorisation, and installation conditions such as height. We measure and quote in writing so you know the full cost before you decide.

Frequently asked questions

This guide is general information from the Royal Decor team. Products, prices and timelines vary, and we confirm them in writing after measuring your site.