To measure your windows for blinds properly, you’ll need to decide whether you want an inside or outside mount, then carefully measure the width and height of the window in multiple places. Accurate measurements are important because even small mistakes can affect how the blinds look, fit, and operate once installed.
Why Accurate Measurements Matter
Getting the measurements right is one of the most important parts of buying new blinds. Even high-quality blinds won’t look good or function properly if the sizing is off.
A better fit improves both appearance and function
Well-fitted blinds:
- Open and close smoothly
- Provide better privacy and light control
- Look cleaner and more professional
On the other hand, blinds that are too small or uneven can leave gaps or sit awkwardly within the frame.
Every window can be slightly different
A lot of people assume all windows are perfectly square, but that’s not always the case—especially in older NZ homes. Measuring in more than one spot helps account for any small variations.
What’s the Difference Between Inside and Outside Mount Blinds?
Before measuring, the first step is deciding how you want the blinds installed.
Inside mount blinds
Inside mount blinds sit neatly within the window frame for a cleaner, more modern appearance.
They’re ideal if you:
- Want a streamlined look
- Have enough window frame depth
- Prefer the blinds to sit flush inside the recess
For inside mounts, accuracy is especially important because the blinds need to fit precisely within the opening.
Outside mount blinds
Outside mount blinds are installed above or around the window frame.
They’re a good option if you:
- Want to make windows appear larger
- Need better light blockage
- Have shallow window frames
Outside mounts are often a little more forgiving when it comes to measurements.
How to Measure Windows for Inside Mount Blinds
Measure the width
Measure the inside width of the window frame in three places:
- Top
- Middle
- Bottom
Use the narrowest measurement to ensure the blinds fit properly.
Measure the height
Next, measure the height in three places:
- Left side
- Centre
- Right side
For height, use the longest measurement.
Check the window depth
You’ll also want to check that your window frame is deep enough for the type of blinds you’ve chosen. Some styles require more recess depth than others.
How to Measure Windows for Outside Mount Blinds
Measure wider than the window
For outside mounts, measure the width you’d like the blinds to cover. Most people add extra width on both sides to improve privacy and reduce light gaps.
Add extra height if needed
It’s also common to extend the blinds slightly above the window frame. This can make windows appear taller and helps block more light when the blinds are closed.
Think about the overall look
Outside mount blinds give you a bit more flexibility visually, so it’s worth stepping back and considering how the finished blinds will look within the room.
Common Mistakes to Avoid
Rounding measurements
Always use exact measurements rather than rounding up or down. Even small differences can affect the fit.
Measuring only once
It’s always worth measuring twice just to be safe. A quick double-check can save a lot of frustration later on.
Using the wrong tools
A steel tape measure is usually the best option, as fabric tape measures can stretch slightly, affecting accuracy.
FAQs
Should I measure in millimetres or centimetres?
Millimetres are usually recommended because they offer greater accuracy, especially for inside-mount blinds where precision matters most.
Can I measure blinds myself, or should I get a professional?
You can absolutely measure blinds yourself if you follow the correct steps carefully. However, for large windows or custom blinds, some homeowners prefer professional measuring for extra peace of mind.
