Accurate measurements are the foundation of a well-fitting custom window shade. This guide explains how to measure for an inside mount or outside mount, what tools to use, and which numbers to submit when ordering custom roller, zebra, cellular, or Roman shades.
Reviewed September 2026. This guide reflects the current SunShieldor product range and ordering requirements. SunShieldor operates its own window shade factory; verify final dimensions, control compatibility and included accessories on the linked product page before ordering.
Before You Measure
Use a steel tape measure, a pencil, and a worksheet. Record every measurement in inches and label each window separately. Do not assume two windows that look identical are exactly the same size.
- Measure each window individually.
- Measure the opening itself, not an existing blind.
- Record width first, then height.
- Measure to the nearest 1/8 inch.
- Do not make your own deductions for an inside mount; submit the actual opening size.
Inside Mount vs. Outside Mount
An inside mount installs within the window opening for a clean, built-in appearance. It requires enough unobstructed depth for the headrail and a reasonably square opening.
An outside mount installs on the wall or trim around the opening. It can cover shallow or uneven openings and may reduce light gaps when enough overlap is added.
How to Measure for an Inside Mount
1. Measure the width in three places
Measure across the inside of the opening at the top, middle, and bottom. Record all three numbers and use the smallest width as your order width. This helps the shade fit even if the window is not perfectly square.
2. Measure the height in three places
Measure from the top of the opening to the sill at the left, center, and right. Use the largest height as your order height so the shade can cover the full opening.
3. Check mounting depth
Measure the clear depth at the top of the window and check for handles, locks, or trim that could obstruct the shade. Product hardware can differ, so contact us before ordering if the opening is shallow.
How to Measure for an Outside Mount
1. Decide how much area to cover
Choose where the headrail will sit and how far the shade should overlap the opening on each side. More overlap generally provides better privacy and light coverage.
2. Measure the finished width
Measure the total width you want the shade to cover, including the planned left and right overlap. Submit this finished shade width rather than the bare window-opening width.
3. Measure the finished height
Measure from the planned top mounting point to the point where the shade should end. Include the space above the opening and any desired overlap below it.
Measurement Checklist
| Mount type | Order width | Order height |
|---|---|---|
| Inside mount | Smallest of top, middle, bottom | Largest of left, center, right |
| Outside mount | Total desired coverage width | Total desired coverage height |
Common Measuring Mistakes to Avoid
- Reversing width and height.
- Rounding to a whole inch instead of using 1/8-inch increments.
- Measuring only once or only in the center.
- Using measurements from an old shade.
- Subtracting from an inside-mount width before ordering.
- Forgetting to check handles, cranks, trim, or mounting depth.
Choose Your Custom Shade
Once your measurements are ready, compare our custom-size shades. Choose a streamlined custom blackout roller shade, flexible light control with a custom zebra shade, an insulating custom cellular shade, or a soft linen-texture custom Roman shade. Each style can be configured as cordless or motorized.
Frequently Asked Questions
Do the same measuring steps apply to Roman shades?
Yes. Use the same inside-mount or outside-mount method for SunShieldor custom Roman shades. Confirm the available mounting depth and enter width first, then height, in inches.
Should I measure in inches or centimeters?
For products sold in the United States, submit measurements in inches. Keep the same unit throughout your worksheet and order.
What if my three width measurements are different?
That is common. For an inside mount, order using the smallest measured width. For an outside mount, order the total width you want covered.
Do I deduct anything for an inside mount?
No. Submit the actual opening measurements. The production allowance is handled during manufacturing for products that require it.
Can I use one measurement for several windows?
Measure every window separately. Small construction differences can affect fit.
What if I am unsure about mounting depth?
Send us a photo and the measured depth before ordering. We can help confirm whether inside or outside mounting is the better choice.