Ordering beautiful new roller shades brings excitement—until the worry about measurements sets in. Getting it wrong can lead to frustrating light gaps, shades that don't operate smoothly, or an unprofessional look. The good news? Measuring like a pro is simple when you know the one rule that changes everything: you must decide how you'll mount the shade before you measure. This isn't just a guide; it's your blueprint for success. We'll walk you through the critical initial choice, then provide two separate, foolproof measurement processes to ensure your new shades fit flawlessly from day one.
Follow this sequence:
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Make The Key Decision: Choose between an inside mount or outside mount.
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Gather Your Tools: You only need two things.
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Follow the Right Path: Use our dedicated steps for your chosen mount.
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Double-Check & Record: Avoid the most common oversight.
Before You Measure: The Critical First Decision
Your entire measuring process hinges on this choice. Don't pick up the tape measure until you've decided. For a comprehensive look at the pros, cons, and aesthetics of each, read our guide on choosing between an inside or outside mount.
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Inside Mount: The shade is installed within the window frame (the recess). It offers a clean, built-in look but requires sufficient depth.
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Outside Mount: The shade is installed on the wall or trim surrounding the window. It makes the window appear larger, can cover unattractive trim, and is best if the recess is too shallow.
Quick Reference:
| If you want... | Choose this mount: |
|---|---|
| A sleek, built-in look with visible trim. | Inside Mount |
| To block more light, cover imperfect frames, or have shallow depth. | Outside Mount |
| To make the window appear larger. | Outside Mount |
What You'll Need & The Golden Rules
Tools:
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A metal tape measure (cloth tapes can stretch and sag).
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A notepad and pen to record every number clearly.
Three Golden Rules of Measuring:
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Measure in Inches: Record to the nearest 1/8th of an inch. Do not round up or down.
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Measure Three Times: Width: measure at the top, middle, and bottom. Height: measure at the left, middle, and right.
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Use the Smallest Measurement: For inside mount, use the smallest width and smallest height you record. This guarantees the shade will fit the tightest spot.
How to Measure for an Inside Mount
An inside mount must fit within the window recess. Precision is non-negotiable.
Step 1: Measure the RECESS WIDTH.
Place your tape measure horizontally inside the window frame.
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Measure from the left interior surface to the right interior surface.
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Measure at the top, middle, and bottom of the recess.
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Record all three numbers. The manufacturer will use the smallest of these to ensure your shade doesn't rub the sides.
Step 2: Measure the RECESS HEIGHT.
Place your tape measure vertically inside the window frame.
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Measure from the top interior surface (where the bracket will go) down to the window sill.
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Measure at the left side, middle, and right side.
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Record all three numbers. Use the smallest height.
Step 3: Check the RECESS DEPTH.
This is often missed but crucial! Measure from the front of the window frame (where the shade will be) back to any obstruction (like a window sash, lock, or handle). The shade mechanism needs this space to fit. If depth is limited, an outside mount may be necessary.
How to Measure for an Outside Mount
An outside mount gives you flexibility. You're determining how much of the wall you want the shade to cover.
Step 1: Determine the SHADE WIDTH.
Decide how far you want the shade to extend past the window glass on each side to prevent light gaps on the sides. We recommend extending at least 1.5 to 2 inches beyond the glass on each side for optimal coverage.
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Measure the exact area you want the shade fabric to cover. This is your "overall shade width."
Step 2: Determine the SHADE HEIGHT.
Decide where you want the top of the shade (the headrail) to be and where you want the bottom to fall.
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For maximum light blockage and a full look, mount the bracket 2-3 inches above the window frame and have the shade extend 2-3 inches below the sill.
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Measure from your chosen top point to your chosen bottom point. This is your "overall shade height."
Step 3: Verify a Flat Surface.
Ensure the area where the brackets will mount is flat and clear. Use a level to check.
Troubleshooting Common Measuring Scenarios
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My window isn't square (width measurements vary). This is normal in older homes. For inside mounts, provide all three widths/heights. The manufacturer will build to the smallest, ensuring it fits. For outside mounts, this is less critical.
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There's a window crank or handle in the way. For inside mounts, measure the clearance depth from the frame to the obstacle. You may need an outside mount. For outside mounts, ensure your chosen width and height clear the obstacle.
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I have trim or molding I want to cover. Use an outside mount. Measure the width and height of the trim itself, then add your desired overhang (e.g., 2 inches per side) to get your final shade dimensions.
Final Checklist & How to Submit Your Measurements
Before you finalize, review this table. Getting your custom roller shades should be exciting, not stressful.
| Task | For Inside Mount | For Outside Mount | ✅ |
|---|---|---|---|
| Mounting Decision Finalized | I have sufficient recess depth. | I want to cover trim or block max light. | |
| Width Recorded | Three widths taken, smallest one noted. | Desired coverage width decided and measured. | |
| Height Recorded | Three heights taken, smallest one noted. | Desired coverage height decided and measured. | |
| Depth/Obstruction Checked | Recess depth measured and meets requirement. | Mounting surface is flat and clear of obstructions. | |
| Units Noted | All figures recorded in inches to 1/8". | All figures recorded in inches to 1/8". | |
| Measurement Double-Checked | All numbers verified one last time. | All numbers verified one last time. |
How to Submit:
When ordering, you will typically provide:
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For Inside Mount: The exact width and exact height (based on your smallest measurements). The manufacturer builds the shade slightly smaller (about 1/4" to 1/2") to ensure operational clearance.
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For Outside Mount: The exact overall width and exact overall height you want the shade to be. The manufacturer builds to these dimensions.
Your Next Steps:
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Make the Mount Choice: Use our guide to choose between inside and outside mount.
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Measure Meticulously: Follow the steps above, or for absolute confidence, use our companion guide on fool-proof measuring with a tape measure.
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Explore Your Options: With your perfect measurements in hand, browse the styles available for custom roller shades.
Explore Custom Roller Shades
Frequently Asked Questions
Should I measure the window myself or have a professional do it?
If you are comfortable with a tape measure and follow this guide carefully, you can measure yourself successfully. However, for very expensive custom shades, complex windows (arches, angles), or if you lack confidence, professional measuring is a wise investment to guarantee perfection.
What is the single most common measuring mistake?
Assuming the window is square and measuring only once. Windows, especially in older homes, are rarely perfectly square. Measuring at only one point often leads to a shade that is too wide for the recess at another point. Always measure width in three places and height in three places.
If I'm ordering multiple shades, do I need to measure each window?
Yes. Measure every single window individually. Even windows that look identical in the same room can vary by a fraction of an inch. Treat each as its own project to ensure a perfect fit for all.
Can I just give you the size of the existing blinds or shades I'm replacing?
This is not recommended. The existing window treatment may not have been the correct size to begin with, or the window itself may have settled or changed. Always take fresh, precise measurements of the window opening or desired coverage area.
I hope this guide has empowered you to measure with confidence. For visual learners or those who want to see the process in action, exploring our other resources on installation and fit can provide additional clarity and ensure your project is a complete success.
