Inside Mount vs. Outside Mount Window Shades

September 12, 2026

Measuring a window for inside-mount or outside-mount custom shades

Quick answer: Choose an inside mount for a clean, built-in appearance when the window opening has enough clear depth. Choose an outside mount when the opening is shallow or uneven, or when you want additional overlap for privacy and light coverage.

Reviewed September 2026. Always use the current product page and the finished dimensions you intend to order.

Inside Mount vs. Outside Mount at a Glance

Mount type	Where it installs	Main advantage	Measurement to submit
Inside mount	Within the window opening	Clean, recessed appearance	Actual opening width and height
Outside mount	On wall or trim around the opening	More coverage and flexibility	Finished shade coverage width and height

When to Choose an Inside Mount

An inside mount keeps the shade within the opening and leaves more trim visible. It works best when the opening is square, deep enough for the headrail and free of handles or locks that could obstruct the shade.

Measure width at the top, middle and bottom.
Use the smallest width as the order width.
Measure height at the left, center and right.
Use the largest height as the order height.
Do not make an extra deduction; submit the actual opening size.

When to Choose an Outside Mount

An outside mount attaches above or around the opening. It is useful for shallow openings, uneven frames and windows where additional overlap may reduce visible light gaps.

Choose the top mounting point.
Measure the total finished width, including overlap beyond the opening.
Measure from the mounting point to the desired lower edge.
Check that trim, handles and nearby furniture will not interfere.

How to Round Measurements to 1/8 Inch

Record every measurement in inches. Round width down to the nearest 1/8 inch and round height up to the nearest 1/8 inch. Measure every window separately even when adjacent windows appear identical.

Download the printable window measurement worksheet (PDF)

Does the Mount Method Change by Shade Style?

The same basic finished-width and finished-height logic applies to SunShieldor roller, zebra, cellular and Roman shades. Headrail depth and hardware can differ, so confirm the current product specifications before ordering.

For the complete illustrated process, read How to Measure Windows for Custom Shades. Then select a custom roller shade, custom zebra shade, custom cellular shade or custom Roman shade.

Frequently Asked Questions

Which mount blocks more edge light?

An outside mount can provide more overlap around the opening, which may reduce visible edge gaps. Results depend on the window, fabric and selected coverage.