How to Measure Windows for Custom Shades

Accurate measurements are essential when ordering custom shades. Before you begin, decide whether the shade will sit inside the window opening or cover it from the outside. That choice determines where you measure and which dimensions you submit. Use a steel tape measure, record every dimension to the nearest 1/8 inch, and measure each window separately—even when several windows appear identical.

Before You Measure

Gather a steel tape measure, pencil, and paper or a measurement worksheet. Avoid using a cloth measuring tape because it can stretch or sag.

Follow these basic rules:

• Record all dimensions in inches to the nearest 1/8 inch.
• Write measurements as width × height, with width first.
• Measure the window itself rather than an existing shade or blind.
• Measure every window individually.
• Check for handles, locks, cranks, trim, tile, or other obstructions.
• Review the product page for minimum mounting depth and bracket requirements.

Label each measurement by room and window position, such as “Primary Bedroom—Left Window.”

Choose an Inside or Outside Mount

An inside mount places the shade within the window opening. It creates a clean, built-in appearance but requires enough unobstructed depth for the headrail and brackets. Because the shade sits inside the opening, some light may remain visible along the sides.

An outside mount attaches to the wall or trim above and around the opening. It is often the better choice when the window is too shallow, noticeably out of square, or obstructed by hardware. It can also provide broader coverage because the shade overlaps the opening.

Before choosing, check the specific product page for minimum depth, flush-mount depth, bracket clearance, and other mounting requirements.

How to Measure for an Inside Mount

1. Measure the Width

Measure the inside width of the window opening in three places:

• Across the top
• Across the middle
• Across the bottom

Record each measurement to the nearest 1/8 inch, then use the narrowest width when ordering. The narrowest measurement helps the shade fit even when the window opening is not perfectly square.

Do not subtract from the width for clearance. Uilvffo makes the necessary deduction for an inside-mount shade. If a specific product page provides different instructions, follow those product-specific requirements.

2. Measure the Height

Measure the inside height in three places:

• Along the left side
• Through the center
• Along the right side

Use the longest of the three measurements. This allows the shade to reach the bottom of the opening even when the sill or frame is slightly uneven.

3. Check the Window Depth

Measure the unobstructed depth at the top of the window opening, where the headrail and brackets will be installed. Use the shallowest available depth if trim, handles, or other hardware reduces the mounting space.

Compare this measurement with the minimum-depth requirement on the product page. A window may have enough total depth but still lack sufficient clear space for the selected shade.

Suggested image placement: Inside-mount diagram showing the three width measurements, three height measurements, and window depth.

How to Measure for an Outside Mount

1. Choose the Mounting Position

Decide where the headrail and brackets will sit before measuring. Confirm that the wall or trim provides a flat, secure mounting surface and enough clearance for the shade to operate.

2. Measure the Coverage Width

Measure the width of the window opening or outer trim, depending on the area you want to cover. Then add the desired overlap.

As a general guideline, extending the shade 1–2 inches beyond the opening on each side can improve coverage and reduce side light gaps. The appropriate overlap may change depending on the product, available wall space, nearby obstructions, and the level of light control you want.

The total coverage width—not just the window opening—is the width you should enter when ordering.

3. Measure the Coverage Height

Measure from the planned top of the headrail to the desired bottom edge of the shade.

If the window has a projecting sill, the shade may end at the sill. If there is no projecting sill, you may extend the shade below the opening for additional coverage. Make sure the finished shade will not interfere with furniture, vents, handles, or the floor.

Suggested image placement: Outside-mount diagram showing the headrail position, side overlap, and top-to-bottom coverage measurement.

Common Measuring Mistakes

Avoid these errors before submitting a custom order:

• Measuring an existing blind instead of the window
• Assuming matching windows have identical dimensions
• Reversing the width and height
• Taking only one inside-width measurement
• Subtracting your own inside-mount allowance
• Ignoring the window’s shallowest depth
• Measuring an outside mount before choosing the bracket position
• Forgetting to account for handles, locks, cranks, or projecting trim

If a measurement falls between 1/8-inch increments, check it again rather than estimating from memory.

Final Measurement Checklist

Before ordering, confirm that:

• Every window is clearly labeled.
• All dimensions are recorded as width × height.
• Measurements use the nearest 1/8 inch.
• The narrowest inside width is recorded.
• The longest inside height is recorded.
• The window depth meets the selected product’s requirements.
• Outside-mount dimensions include the intended overlap.
• No manual deduction has been made for an inside mount.
• Every measurement has been checked a second time.

Accurate measuring begins with the mounting method. For an inside mount, use the narrowest width, longest height, and shallowest unobstructed depth. For an outside mount, measure the complete area you want the shade to cover.

Product requirements can vary, so review the selected shade’s specifications before ordering. For diagrams and additional instructions, see the Uilvffo window measuring guide or contact Uilvffo support if your window has an unusual shape or limited mounting space.