How to Measure Your Windows for Plantation Shutters: A Complete Guide for Every Window Type

Accurate measurements are the most important step when ordering custom plantation shutters. Even a small measuring error can cause shutters to fit poorly, leave visible gaps, or prevent panels from closing properly.

This window measuring guide explains how to measure for plantation shutters across common window types, including standard windows, bay windows, arched windows, and sliding glass doors.

Accurate DIY shutter measurements depend on understanding mounting style, window depth, and frame structure. Whether installing an inside mount or outside mount shutter, the same measurement principles apply.

Tools You’ll Need Before Measuring

Using the correct tools helps ensure precision shutter sizing.

Recommended tools include:

• Steel tape measure for accurate measurements
  
• Laser measure for tall or wide openings
  
• Notepad and pencil to record measurements immediately
  
• Level to check whether the window frame is square

Plantation shutters are custom fabricated, so measurements should be recorded carefully down to fractions of an inch.

Step 1: Choose Inside Mount or Outside Mount

Before measuring, determine whether the shutters will use an inside mount or outside mount installation.

• Inside mount shutters sit inside the window recess.
  
• Outside mount shutters attach to the wall or trim surrounding the window.

This decision determines which measurements you will use when ordering shutters.

When to Choose an Inside Mount

Inside mount shutters sit within the window frame, creating a clean, built-in appearance. This style is common because it preserves the window trim and keeps the shutters aligned with the interior frame.

Inside mount installations work best when the window frame is square and deep enough to hold the shutter frame and louvers.

Before choosing inside mount shutters, check for hardware such as locks, handles, or cranks that may interfere with shutter movement.

When to Choose an Outside Mount

Outside mount shutters attach to the wall or trim surrounding the window.

This option is useful when:

• The window recess is shallow
  
• The window frame is uneven or out of square
  
• The window has an unusual shape

Outside mount frames can also hide irregular window edges and create a more symmetrical appearance.

Measuring Inside Mount Plantation Shutters

Inside mount shutters require measurements taken directly inside the window opening.

Check Window Squareness (Diagonal Test)

A square window frame will have equal diagonal measurements.

To check:

1. Measure from the top-left corner to the bottom-right corner
   
2. Measure from the top-right corner to the bottom-left corner

If the measurements are very close, the frame is generally square and suitable for inside mount shutters.

If there is a large difference between the diagonals, an outside mount installation may provide a better fit.

Use the 3-Point Measuring Method

Window openings often vary slightly in size. The 3-point method helps identify the narrowest areas of the frame.

Measure width in three places:

• Top of the opening
  
• Middle of the opening
  
• Bottom of the opening

Measure height in three places:

• Left side
  
• Center
  
• Right side

For inside mount shutters, always use the smallest measurement recorded for width and height.

You should also measure window depth, which is the distance from the front of the frame to the glass. Adequate depth is required for the shutter frame and louvers.

Measuring for Outside Mount Shutters

Outside mount shutters require measuring the space the frame will cover rather than the interior recess.

Measure the total width and height of the window opening, including trim if applicable.

Outside mount frames typically overlap the opening slightly to reduce light gaps.

For outside mount shutters, use the largest measurement recorded so the frame fully covers the window opening.

Frame styles such as L-frames or Z-frames may also influence how the shutters attach to the wall or trim.

Measuring Special Window Types

Some window styles require additional measurements.

Custom plantation shutters from Shutter Supplies can be made for a wide range of window shapes and sizes.

Bay and Bow Windows

When measuring bay windows for shutters, measure each section of the window individually rather than measuring the entire structure as one opening.

Record the width and height of every panel section and note the angle where the windows connect.

Bow windows follow a similar process, although the panels usually form a smooth curve rather than sharp angles.

Arched and Shaped Windows

Arched windows require several measurements:

• Full width of the window
  
• Height of the rectangular section below the arch
  
• Height from the start of the curve to the highest point

These measurements define the shape needed for arched plantation shutters.

Sliding Glass Doors

Sliding glass door shutters require:

• Full height from floor to the top of the door frame
  
• Total width of the door opening

You should also check where the door panels slide so the shutter panels can open without blocking the door.

For partial coverage, cafe plantation shutters may be used. In this case, measure only the lower portion of the window.

Measuring Mistakes That Cause Costly Remakes

Because plantation shutters are custom built, incorrect measurements can result in shutters that do not fit properly.

Common measuring mistakes include:

• Skipping the diagonal squareness test
  
• Taking only one width or height measurement
  
• Forgetting to measure window depth
  
• Ignoring hardware that may block the louvers
  

FAQs

What is the minimum window depth for plantation shutters?

Inside mount shutters require enough recess depth to fit the frame and louvers. Outside mount shutters do not depend on recess depth because they attach to the wall or trim.

Do I use the smallest or largest measurement?

Use the smallest measurement for inside mount shutters so the frame fits inside the opening. Use the largest measurement for outside mount shutters to ensure full coverage.

What if my window frame is not square?

Minor variations are common. Small differences may still allow inside mount shutters, while larger differences may require outside mount installation.

📞 Call 281-704-3838 to get professional advice or request a quote for custom plantation shutters from Shutter Supplies and ensure your measurements are accurate before ordering.