How to Measure for Roller Blinds (Quick & Accurate)

Learning how to measure for roller blinds is the first step to transforming your windows—and it’s easier than you think! While it might feel a bit intimidating at first, getting those measurements right is absolutely worth it. Why? Because a perfectly measured blind means no awkward gaps, no costly returns, and no frustration. Instead, you’ll enjoy blinds that fit like a glove, giving you privacy, light control, and a polished, professional look. This guide will walk you through every step, from deciding between inside and outside mounts to spotting potential obstacles. By the end, you’ll feel like a pro, ready to measure with confidence and ensure your custom blinds from Brighter Blinds and Doors fit flawlessly.

Inside vs. Outside Mount: Which Do You Need?

Before you even grab your tape measure, you’ll need to decide how you want your blinds to hang. There are two main options: inside mount and outside mount.

• Inside Mount: This style fits the blind snugly inside the window frame, creating a clean, built-in look. It’s a popular choice because it highlights your window trim beautifully. If this is your pick, you’ll need to know how to measure for roller blinds inside mount specifically. For more inspiration, check out our range of roller blinds and indoor blinds.
• Outside Mount (or “Exact Fit”): Here, the blind is mounted on the wall above and around the window frame. This option is perfect if an inside mount isn’t possible or if you want to block out more light.

Choose an outside mount if:

• You want blackout blinds to eliminate light gaps.
• Your window recess is too shallow for the blind’s hardware.
• You want to cover decorative window trim completely.
• There are obstructions like handles or alarm sensors inside the frame.

For outdoor solutions, such as outdoor blinds or roller shutters, an outside mount is often the best choice.

Tools You’ll Need

Having the right tools on hand makes the process smooth and stress-free. Here’s what you’ll need:

• Steel Tape Measure: This is non-negotiable. Cloth or flexible tape measures can stretch, leading to inaccurate readings.
• Step Ladder: For safely reaching tall windows.
• Pencil: To mark your measurements.
• Notepad or Smartphone: To jot down your numbers clearly. Label each one (e.g., “Kitchen Window Top Width”) to avoid mix-ups.

Quick safety note: Modern blinds are designed with child safety in mind. At Brighter Blinds and Doors, our professional installation includes securing chains and using tensioners to eliminate hazards, so you can have peace of mind. If you’re considering alternatives like sheer curtains for a softer look, we’ve got you covered.

How to Measure for Roller Blinds (Inside Mount)

If you’ve chosen an inside mount for that sleek, recessed look, follow these three steps for a perfect fit. The key is to measure multiple points, as window frames are rarely perfectly square.

1. Measure the Width
   Measure the horizontal width inside the window frame at three different points:
   
   • Across the top
   • Across the middle
   • Across the bottom

Circle the smallest of these three measurements. This is the width you’ll use. Using the narrowest measurement ensures the blind won’t scrape the sides of the frame. This step is critical when learning how to measure for roller blinds inside mount.

1. Measure the Drop (Height)
   Next, measure the vertical height of the window frame opening. Again, do this in three spots:
   
   • Down the left side
   • Down the center
   • Down the right side

Circle the smallest measurement. This ensures the blind won’t bunch up on the windowsill.

1. Measure the Recess Depth
   Finally, measure the depth of your window frame from the front of the opening back to the glass or any obstruction. This is crucial because the blind’s headrail and brackets need a minimum amount of flat mounting surface. Check the product specifications for the minimum recess depth required. If your recess is too shallow, you’ll need to opt for an outside mount.
   

Pro Tip: “Exact” vs. “Fabric” Width
When ordering, pay close attention to the terminology. If a supplier asks for the “exact” measurement, they want the precise recess width you recorded. They’ll make the necessary deductions (usually 10–15mm) to ensure the blind fits. If they ask for the “fabric width”, they want you to calculate the fabric size yourself. When in doubt, provide the exact recess measurement and let the experts handle the deductions.

How to Measure for Roller Blinds (Outside Mount)

For an outside mount, you’re measuring the total area you want the blind to cover. This is often called an “exact fit” because the manufacturer will make the blind to the exact dimensions you provide, with no deductions.

1. Measure the Width

Measure the width of the area you want to cover. To minimize light leakage and ensure privacy, add at least 50mm (2 inches) of overlap to each side of the window frame. For example, if your window frame is 1000mm wide, your finished blind width should be at least 1100mm (1000mm + 50mm + 50mm).

1. Measure the Drop (Height)

Decide where you want the blind to end—whether it’s the bottom of the windowsill, the floor, or somewhere in between. Measure from the spot where you’ll mount the headrail (typically 50–100mm above the frame) down to your desired endpoint. The extra height at the top helps block more light and gives a balanced look.

For outdoor spaces, consider pairing your blinds with awnings or shade sails for added comfort and style.

Depth, Brackets, Cassettes & Rounding Rules

 Details matter when it comes to a flawless installation.

• Minimum Recess Depth: Always check the product specifications. A standard roller blind might need 60mm of depth, while one with a decorative cassette could require 80mm or more.
• Bracket & Fabric Gaps: Remember, the fabric will always be slightly narrower than the headrail to accommodate the brackets and control mechanism. This gap is usually around 20–25mm on the control side and slightly less on the other.
• Rounding Rules: Follow the supplier’s instructions precisely. Some may ask for measurements to the nearest millimeter, while others (especially in the US) might use fractions like the nearest 1/8″. For inside mounts, it’s always safest to round down if you’re between measurements.

Check for Problems & Obstructions

 Before finalizing your order, do one last check of the window area:

• Do window handles, locks, or air vents stick out?
• Are there tiles or skirting boards making the frame uneven?
• Is there a radiator below the window that could interfere with a full-length blind?
• Decide which side you want the control chain on. Is it easy to reach?
• Consider motorized options if the window is hard to access.

Common Mistakes & How to Avoid Them

• Using a cloth tape measure: They can stretch. Always use a steel one.
• Measuring only once: Window frames are rarely perfectly square. Measure thrice.
• Ignoring recess depth: This is a common reason inside mount blinds don’t fit.
• Forgetting about obstructions: Handles and vents can stop a blind in its tracks.
• Mixing up width and height: Label your measurements clearly as you go.

Measure Twice, Order Once — Or Let a Pro Do It

Feeling confident? Great! Grab your tape measure and get started. But if you’re still a bit hesitant, don’t worry. At Brighter Blinds and Doors, we want to ensure your window coverings are perfect from the start. We offer a free measure and quote service across Melbourne. Our experts will handle everything, ensuring a flawless fit every time. Contact us today to get started!