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How to Measure Your Windows Like a Pro

Measuring your windows correctly is the first step to ensuring your new blinds fit perfectly and look professional. Whether you’re installing Roller, Venetian, or Roman blinds, accurate measurements make all the difference between a seamless finish and a frustrating redo. With a few simple tools and the right method, anyone can measure like a pro.

What You’ll Need

Before you start, gather a steel measuring tape, pencil, paper, and a step ladder if your windows are tall. Always measure in millimetres (mm) for the most precise results—this is the standard measurement used by most blind manufacturers in New Zealand.

Step 1: Decide on Inside or Outside Mount

The first decision when measuring for blinds is whether they’ll be inside-mounted or outside-mounted.

• Inside mount: The blind fits neatly within the window frame for a streamlined look. This is ideal for modern interiors and when you want to showcase your window trim.
  
  

• Outside mount: The blind is installed on the wall or architrave, covering the entire window area. This approach is perfect for increased light blockage or when your frame isn’t perfectly square.
  
  

Choose the mount type that best suits your style and functional needs before taking any measurements.

Step 2: Measuring for an Inside Mount

For an inside mount, measure the width and the drop (height) of the inside recess in three places—top, middle, and bottom for width; left, centre, and right for drop.

• Record the smallest width and the longest drop.
  
  

• Double-check your measurements to the nearest millimetre.
  
  

This ensures your blinds fit neatly within the recess, without scraping or sticking.

Tip: Check that the recess is deep enough to accommodate your chosen blind. Roller blinds, for example, require sufficient clearance for the mechanism to operate smoothly.

Step 3: Measuring for an Outside Mount

If you prefer an outside mount, measure the exact area you’d like the blind to cover.

• For width, extend the measurement at least 50–100 mm beyond each side of the window frame to block more light.
  
  

• For drop, start from where the blind will be fixed (above the window) and measure to your preferred endpoint—typically the bottom of the sill or slightly below for a more tailored look.
  
  

Outside mounting is a great option for bedrooms or media rooms where full light control is essential.

Step 4: Double-Check and Label Each Window

If you’re measuring multiple windows, label each one clearly—“Living Room Left” or “Bedroom 2 Right”—so it’s easy to match your measurements later. Recheck each figure before ordering.

Common Mistakes to Avoid

• Rounding measurements—always record the exact millimetre.
  
  

• Mixing up width and drop dimensions.
  
  

• Assuming all windows are identical, measure each one individually.
  
  

Accurate measuring ensures your blinds fit perfectly and function as they should. In New Zealand, most blind suppliers, including professional installers, base their manufacturing on your provided measurements, so precision matters. By following these simple steps and choosing the right mount, you’ll achieve a flawless, made-to-measure result—just like a pro.

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Nov 25, 2025