Getting accurate measurements for your roller blinds is the single most important step in achieving a professional-looking window treatment. Whether you're ordering custom blinds or purchasing ready-made options, precise measurements ensure a perfect fit that maximises light control, privacy, and energy efficiency.
Key Takeaway
Always measure twice and record in millimetres for Australian suppliers. A 10mm error can mean the difference between a perfect fit and an unusable blind.
Understanding Mount Types: Inside vs Outside Mount
Before you pick up your tape measure, you need to decide how you want your roller blinds mounted. This decision affects not only aesthetics but also how much light blocking and privacy you'll achieve.
Inside Mount (Recess Mount)
An inside mount sits within the window recess, creating a clean, built-in appearance. This option works best when you have a deep enough recess (minimum 50mm depth for most roller blinds) and want to showcase decorative window frames or architraves.
For inside mount installations, you'll need to measure:
- Width: Measure the inside width of the window recess at three points—top, middle, and bottom. Use the smallest measurement to ensure the blind fits without jamming.
- Height: Measure the inside height of the recess from the top to the windowsill at three points—left, centre, and right. Use the longest measurement to ensure full coverage.
- Depth: Measure the depth of the recess to confirm it can accommodate the blind mechanism (typically 45-75mm required).
Outside Mount (Face Mount)
An outside mount attaches to the wall or window frame above the recess. This option provides better light blocking, as it covers gaps around the window, and works well for shallow recesses or when you want to make windows appear larger.
For outside mount installations:
- Width: Measure the total width you want to cover. We recommend adding 50-100mm on each side of the window frame for optimal light blocking.
- Height: Measure from your desired mounting height (typically 100-150mm above the frame) down to the windowsill or your preferred drop length.
Pro Tip
For bedrooms where maximum light blocking is essential, always choose an outside mount with generous overlap. This prevents light leaking around the edges and improves your sleep quality.
Essential Tools for Accurate Measurement
Using the right tools makes the measuring process significantly easier and more accurate. Here's what you'll need:
- Steel tape measure: A 5-metre steel tape provides accuracy and doesn't stretch like fabric measures. Look for one with clear millimetre markings.
- Step ladder: Essential for safely reaching the top of windows and measuring height accurately.
- Pencil and notepad: Record measurements immediately—don't rely on memory.
- Spirit level: Check that windowsills and frames are level. Uneven surfaces may require adjustments.
Common Measurement Mistakes to Avoid
Even experienced DIYers make measurement errors. Here are the most common mistakes and how to avoid them:
Mistake 1: Measuring Only Once
Australian homes, especially older properties, often have windows that aren't perfectly square. Walls settle over time, and what looks like a rectangular window may actually vary by 10-20mm from top to bottom or side to side.
Mistake 2: Using the Wrong Units
Most Australian blind suppliers work in millimetres. Converting from centimetres or inches introduces opportunities for error. Measure and order in millimetres to eliminate confusion.
Mistake 3: Forgetting to Account for Obstructions
Check for window handles, locks, or sensors that might interfere with the blind mechanism. For inside mounts, ensure these don't prevent the blind from rolling up completely.
Mistake 4: Not Checking for Square
Use your tape measure diagonally from corner to corner in both directions. If the measurements differ by more than 5mm, your window isn't square, and you may need to adjust your approach or consult a professional.
Australian Building Standards
Modern Australian homes built to current building codes typically have more consistent window dimensions than older properties. However, always measure rather than assume—even new builds can have variations.
Step-by-Step Measuring Process
Follow this systematic approach for each window:
- Identify your mount type based on recess depth and aesthetic preferences.
- Clear the window area of curtains, plants, or furniture that might interfere with accurate measurement.
- Measure width at three horizontal points and record the smallest (inside mount) or add your desired overlap (outside mount).
- Measure height at three vertical points and record the longest measurement.
- Check and record recess depth for inside mounts.
- Note any obstructions that might affect installation.
- Double-check all measurements before ordering.
Special Considerations for Australian Windows
Australian homes feature several window types that require specific measuring approaches:
Bay Windows
Measure each section of a bay window separately. The angled sections may require individual blinds that meet at the corners.
Bi-Fold Doors
Large bi-fold door openings often benefit from multiple blinds rather than one oversized unit. Consider how the blinds will stack when open and whether they'll obstruct the folding mechanism.
Skylights
Skylight roller blinds require precise measurements and often specialised tracks to hold the fabric in place at an angle. Always measure the actual glass area and consult with suppliers about skylight-specific products.
When to Call a Professional
While DIY measuring is suitable for most standard windows, consider professional measurement services for:
- Unusually shaped or very large windows
- Historic homes with non-standard window configurations
- Motorised blind installations requiring electrical considerations
- Commercial properties or high-value custom orders
Many Australian blind retailers offer free in-home measuring services for orders over a certain value—take advantage of these when available to ensure a perfect fit.