10 Measurements to Make Before Buying Your New Window Coverings

Window coverings can dramatically elevate a room’s look, add privacy and enhance energy efficiency. Whether you're choosing blinds, curtains or shutters, accurate measurements are essential for a seamless installation. Inaccuracies can lead to awkward fits, reduced functionality and unexpected costs.

Before you place an order, you’ll want to know your window dimensions down to the millimetre. This guide walks you through how to measure correctly, accounting for inside and outside mounts, frame types, hardware and architectural elements.

1. Identify Your Window Frame Type

Start by examining the frame style of your window. Some windows have wide, ornate frames while others are sleek and minimal. This difference affects how and where your window coverings will sit. Wider frames may suit outside mounts, while slim frames often pair best with inside fits.

Timber and aluminium frames also vary in thickness, influencing both measurement and installation methods. You’ll need to account for how hardware interacts with the material. In some cases, thicker frames might require deeper recesses or longer screws to secure the fittings safely.

By understanding your frame type, you’ll avoid costly returns, misaligned hardware and misfitting window coverings. It also makes it easier to select the right mounting option for your style and functional needs.

2. Measure for Inside Mounts With Precision

If you want your window coverings to sit within the frame, you’ll need accurate inside mount measurements. Measure the window width at the top, middle and bottom, and record the narrowest point. This ensures your covering won’t get stuck or sit unevenly.

Use a metal tape measure for best results, as fabric ones can stretch or flex. Also check for obstructions inside the frame such as handles or locks, which can impact the fit or movement of blinds or shades.

Depth is another important consideration. Some blinds or shutters require a minimum clearance to function properly. Always check the depth of the recess and confirm whether your chosen coverings are compatible with that space.

3. Allow for Extra Width With Outside Mounts

For outside mounts, measure the width of your window and then add 3 to 6cm on each side. This overlap ensures total light coverage and boosts privacy—particularly useful in bedrooms or living areas.

Outside-mounted window coverings are ideal for shallow windows or frames with protrusions. They also help create the illusion of larger windows and are more forgiving of minor measurement discrepancies.

Make sure to consider surrounding elements such as furniture, adjacent walls or light switches. These can affect where you install the brackets and how far your coverings should extend.

4. Account for Overlaps to Control Light

Planning for overlap is essential in ensuring your window coverings are effective. A good rule of thumb is to allow 2 to 5cm of coverage beyond the window on each side to block unwanted light seepage.

This extra coverage not only improves privacy but also helps maintain indoor temperature by limiting heat loss or gain. In spaces like media rooms or bedrooms, it can create near-blackout conditions when needed.

Overlap is also useful when your windows are positioned close together or have furniture nearby. Extending your curtains or blinds just beyond the window frame makes the space look more generous and cohesive.

5. Choose Hardware That Supports Style and Strength

Selecting the right hardware is just as important as choosing the window coverings themselves. It determines how securely the coverings are installed, how they operate and how they look within your space.

You’ll need to consider the weight and type of your coverings. For instance, heavier drapes require sturdy metal rods or brackets, whereas light roller blinds can often be supported by basic plastic fittings. Always check weight ratings when purchasing.

Also consider aesthetics—hardware comes in a range of finishes from brushed steel to painted timber. Matching these to your window coverings and interior décor can unify the design and enhance the room’s visual appeal.

6. Measure Window Height for Inside Mounts

To measure height for an inside mount, take three vertical measurements—left, middle and right—inside the window frame. Use the shortest length to avoid obstructing mechanisms like sills or handles.

This measurement is particularly important for blinds and roller shades that need space to retract properly. A short or tight fit may cause uneven movement or leave light gaps.

Look for irregularities in your window shape or sill. Even minor tilts or curves can impact fit and appearance. Recording these accurately helps you decide if minor adjustments or professional installation might be needed.

7. Extend Height for Outside Mounts

Outside mounts offer more visual flexibility. Measure from where you plan to install the top bracket (often above the frame) to where you want the window covering to end. For floor-length curtains, you might go all the way to the floor, or even allow a few centimetres for a "puddling" effect.

Longer drops can add grandeur to a space or make windows appear taller. On the other hand, more modest heights suit compact rooms or windows positioned above furniture.

Be consistent with your measurement points—measuring from uneven flooring or trim can lead to crooked installations. Plan around fixed elements like cornices or ceiling heights to get a clean look and avoid clash with existing architecture.

8. Factor in Window Orientation and Room Use

Light exposure differs throughout the day, especially for windows facing east or west. Knowing how sunlight enters your room will help you choose both the type and coverage of your window coverings.

For example, if your window faces the morning sun, you may want thicker blinds or double-lined curtains to block out harsh light. In contrast, a south-facing window may need less coverage but more aesthetic presence.

Think about the room’s function as well. Living areas may benefit from light-filtering shades that offer privacy without sacrificing daylight. Bedrooms typically need more opacity. Matching your window coverings to these needs enhances comfort and function.

9. Be Mindful of Standard Window Sizes

Although window sizes vary by home, knowing common dimensions can be helpful. According to Habitus Living , the standard size for a sliding window is 60cm by 210cm. This reference can help guide your initial planning or serve as a benchmark if your windows are custom-sized.

By understanding typical sizes, you can more easily compare covering options or identify whether you’ll need made-to-measure solutions. Most retailers provide standard and custom sizing, but it's still vital to measure your actual windows instead of assuming they’re standard.

10. Prepare for Obstacles and Final Adjustments

Consider everything near the window that could impact your installation. This includes cornices, dado rails, skirting boards, radiators or even furniture placement. Each could potentially obstruct the movement of your window coverings or create visual imbalance.

Before committing to a purchase, walk through the installation path and envision how the coverings will move. Will there be enough clearance for sliding or pulling? Will cords or controls be easily reachable? Pre-emptively addressing these questions ensures a better fit.

Also factor in cleaning and maintenance. Some fabrics and mechanisms are easier to manage in larger windows, while others suit small or high-set openings. Getting it right the first time saves money and time down the track.

Purchasing window coverings isn't just about choosing a colour or pattern—it’s about precision. Taking the time to properly measure width, height and depth ensures your coverings will look beautiful, function smoothly and last longer.

Whether you’re working with inside or outside mounts, accurate measurements prevent problems like light seepage, awkward fits and difficult installation. They also help you select hardware that works with your coverings and suits your décor. Every element, from overlap to orientation, plays a role in achieving the perfect fit.

Incorporating well-fitted window coverings elevates not only the appearance but also the comfort of your living space. From improving privacy to managing natural light, the right measurements ensure your new additions meet every need.

Ready to upgrade your space with stunning, perfectly-fitted window coverings? Contact Windsor Blinds Awnings Shutters today for expert advice, custom solutions and professional service tailored to your home.