How to Measure Windows for Exterior Shutters

Your Measuring Toolkit

Getting new exterior shutters is one of the fastest ways to boost your home's curb appeal — but only if they fit. Shutters that are too short or too narrow look off regardless of style or color. Knowing how to measure for shutters before you order saves you money, time, and frustration. The goal is simple: measure your windows accurately so you get shutters to fit every opening on the first try.

You don't need much:

• Steel tape measure — more accurate than fabric or plastic
• Pencil and notepad — write measurements down immediately; don't rely on memory
• Ladder — for upper-floor windows

That's it. Two people make the job easier, especially on taller windows.

Step 1: Measure the Shutter Height

Height is the measurement that matters most when you measure for exterior shutters. Getting the shutter height wrong (almost always too short) is the most common sizing mistake homeowners make.

When measuring the height, start at the bottom of the window and run your tape to the top of the window casing (the trim surrounding the frame). Do this on both the left and right sides, since window size varies even within the same house. Use the smaller of the two measurements.

Step 2: Measure the Shutter Width

Each shutter sits on one side of the window, so you're determining the width of a single panel, not the full window. The right way to measure window shutters is to always work from the window opening, not the overall window frame.

When measuring the width of your window, take the measurement at the opening only, not the casing. For the most proportional look, each shutter should be approximately half the width of the window. This way, if the shutters were functional, they'd close to cover the window completely – which is exactly the visual you're going for, even with decorative shutters.

Use this quick reference:

Decorative vs. Functional Shutters: Does It Change How You Measure?

For decorative shutters – the kind most homes have today – you measure as described above. The goal is proportion: the shutter should look like it could close over the window.

For functional shutters that actually open and close, measure the window opening only (not the casing) and subtract ¾" from the total pair width and ½" from the height to allow clearance for the hardware.

The same principle applies when you measure for outside shutters on historic or coastal homes where shutters still need to operate. For taller mounted shutters, consider adding divider rails – horizontal breaks that split the panel into two independently operating sections for better light control.

Measuring for plantation shutters follows a similar sizing logic, but interior window treatments like these also require a depth measurement to ensure the frame fits within the window recess. Material matters here too: faux wood shutters are a popular choice because they hold their shape in humid conditions and are easy to clean — a practical advantage exterior vinyl can't match indoors.

Window shutters come in all these types, and the measuring foundation is the same – functional sizing just adds a layer of precision on top.

Measuring for Special Windows

Arched or Radius-Top Windows

You'll need two height measurements: the high point (bottom to the peak of the arch) and the low point (bottom to where the curve begins). Width is measured the same way as a standard window.

Double or Wide Windows

Treat a double window as one unit. Measure the full combined width, divide by two, and that's your shutter width. Sizing each individual pane separately throws off the proportions across the whole opening.

Common Measuring Mistakes to Avoid

• Measuring only once. Windows are rarely perfectly square. Always take two width measurements (top and bottom) and two height measurements (left and right).
• Forgetting the casing. For decorative shutters, height should include the window trim, not just the glass.
• Assuming all windows are the same size. Even windows that look identical can differ by half an inch or more. Measure every one.
• Rounding down on height. When in doubt, go up a size. A shutter that's slightly taller looks intentional. One that's too short looks like a mistake.

If you're updating the look of your home in the Midwest, Feldco offers vinyl window shutter replacement across Illinois, Wisconsin, Michigan, Iowa, and Indiana. Whether you want to paint shutters to match a new color scheme or replace them entirely, getting the measurements right is always the first step. Get a free quote today!