How to Measure Your Windows for Shutters

Proper window measurements are essential for ensuring your California shutters fit perfectly. While Canadian Shutters always provides free professional measuring during our in-home consultation, understanding the process helps you plan your project and get an accurate price estimate. This guide walks you through measuring for both inside mount and outside mount shutters.

Tools You Will Need

• Steel tape measure (cloth tape measures can stretch and give inaccurate readings)
• Pencil and notepad (or your phone's notes app)
• Step stool or ladder for high windows
• Level (optional but helpful for checking if window frames are square)

Inside Mount Measuring — Step by Step

Inside mount shutters are installed within the window frame, creating a clean, built-in appearance. This is the most popular option for most Toronto and GTA homes.

Step 1: Measure the Width

Measure the inside width of the window frame at three points: the top, the middle, and the bottom. Record all three measurements to the nearest 1/16 of an inch. Use the narrowest of the three measurements — this ensures your shutters will fit within the frame at its tightest point.

Step 2: Measure the Height

Measure the inside height of the window frame at three points: the left side, the centre, and the right side. Again, record all three and use the shortest measurement. This accounts for any unevenness in the frame that might prevent your shutters from fitting properly.

Step 3: Check the Depth

Measure the depth of the window frame from the front edge to the glass or any window hardware. For inside mount shutters, you need a minimum depth of approximately 2.5 inches for 2.5-inch louvers and 3.5 inches for 3.5-inch louvers. If your frame is too shallow, outside mount may be the better option.

Step 4: Check for Square

Use a level to check if the top and sides of the window frame are level and plumb. If the frame is significantly out of square, note this — our professional installers can accommodate minor variations, but it is important information for manufacturing.

Outside Mount Measuring — Step by Step

Outside mount shutters are mounted on the wall or moulding around the window. This is ideal when the frame depth is insufficient for inside mount, or when you want the window to appear larger. Outside mount requires an additional frame, priced at $5 per linear foot of perimeter.

Step 1: Measure the Width

Decide how far beyond the window opening you want the shutters to extend on each side. We recommend at least 1.5 inches of overlap on each side for proper light blocking and coverage. Measure from your desired left edge to your desired right edge.

Step 2: Measure the Height

Decide how far above and below the window opening you want coverage. We recommend at least 1.5 inches above and below. Measure from your desired top edge to your desired bottom edge.

Step 3: Check the Mounting Surface

Ensure the wall or moulding around the window is flat and can support mounting screws. Note any obstructions like handles, locks, or trim that might interfere with the shutter frame.

Inside Mount vs. Outside Mount — Which Should You Choose?

Inside mount is preferred by most homeowners because it creates a clean, seamless look where the shutters sit flush within the window frame. It also preserves the window trim and moulding. Choose inside mount when your window frames have adequate depth and are reasonably square.

Outside mount is the better choice when window frames are too shallow, significantly out of square, or when you want to create the illusion of larger windows. Outside mount also works well for covering multiple narrow windows with a single shutter panel for a unified look.

Pro Tips for Accurate Measuring

• Always use a steel tape measure, never a cloth one — accuracy matters at this scale.
• Measure each window individually, even if they appear identical. Windows in the same room can vary by significant amounts.
• Record measurements in inches and fractions, not centimetres, as this is the industry standard in North America.
• Note the location of each window (e.g., "master bedroom, left window") alongside its measurements.
• Check for any obstructions inside the frame: handles, cranks, sensors, or locks that might interfere with shutter operation.
• If measuring for a bay window or corner configuration, note the angle between window sections.

Common Mistakes to Avoid

• Measuring only once: Always measure at three points for both width and height. Windows are rarely perfectly square.
• Using the largest measurement: For inside mount, always use the smallest width and smallest height to ensure the shutters fit.
• Forgetting to check depth: Insufficient frame depth is the most common reason homeowners need to switch from inside to outside mount.
• Measuring moulding instead of opening: For inside mount, measure the inside of the frame opening, not the outer edge of the moulding.
• Not accounting for obstructions: Window cranks, locks, and alarm sensors can all interfere with shutter operation if not accounted for.

Skip the Guesswork — Get Free Professional Measuring

While this guide gives you a solid foundation for estimating your project, nothing replaces professional measurement by an experienced installer. At Canadian Shutters, we provide free in-home consultations throughout the GTA where our team measures every window with precision tools, identifies any potential challenges, and provides a detailed quote on the spot. Try our online price calculator for an instant estimate, or book your free consultation today.