Let's be real - I messed up my first window shade measurement. Ended up with gaps that let in light exactly where I didn't want it. Had to wait weeks for replacements too. That's why I'm writing this guide - so you don't suffer like I did. Getting measurements right for window shades and blinds is 90% of the battle.
Before You Grab That Tape Measure
First things first. You need to know where those blinds or shades will sit. This changes everything about how to measure for window shades and blinds.
Mounting Types Demystified
| Mount Type | Where It Sits | Best For | My Personal Take |
|---|---|---|---|
| Inside Mount | Inside window frame | Clean look, shows off trim | My favorite for modern homes |
| Outside Mount | On wall above window | Covering drafts/hiding flaws | Life-saver in my old apartment |
Check your window depth before committing to inside mount. For wood blinds, you need at least 2.5 inches. Less than that? Outside mount is your friend.
Gut Check: Measure every single window even if they look identical. In my last house, twin windows differed by ¼ inch. Just enough to cause headaches!
Tools That Actually Matter
- Steel tape measure (cloth tapes stretch - trust me, I learned the hard way)
- Notebook and pencil (phone notes get deleted)
- Step ladder for high windows
- Flashlight to see recesses clearly
The Step-by-Step Measurement Process
How to Measure for Inside Mount Blinds and Shades
Pro Tip: Measure at the front of the recess where the blind will sit - not the back!
- Measure width in three places (top/middle/bottom). Write them all down
- Measure height in three places (left/center/right)
- Use the smallest measurement of each. Manufacturers deduct ¼-½" anyway
My kitchen window example: Top width 35.5", middle 35.25", bottom 35.5". I ordered 35" wide blinds. Perfect fit.
How to Measure for Outside Mount Window Treatments
Here's where you get creative coverage:
- Decide overlap (I add 3-4" per side for light blockage)
- Measure exact width where brackets will go
- Add overlap to height measurement (top and bottom)
| Overlap Purpose | Minimum Overlap | My Recommended Overlap |
|---|---|---|
| Basic coverage | 1.5" per side | 2" per side |
| Block light leaks | 3" per side | 4" per side |
| Cover bad trim | Measure flaw + 1" | Measure flaw + 2" |
Special Window Situations
Measuring Bay Windows for Shades
Bay windows require trigonometry? Not quite:
- Measure each window separately
- Note angles between sections (take photos!)
- Specify mounting surface (ceiling vs. wall)
I once saw someone order single shade for curved bay - total disaster. Don't be that person.
French Doors and Sliding Glass Doors
- Mount inside the door frame
- Account for handles in height measurements
- Consider top-down shades for privacy control
Critical Mistakes to Avoid
After helping dozens of friends, here's where people slip up:
| Mistake | Result | How to Avoid |
|---|---|---|
| Assuming level windows | Uneven gaps | Measure height in 3 places |
| Ignoring obstructions | Blinds won't operate | Check for window cranks/tracks |
| Measuring only once | Ordering wrong size | Measure twice, order once |
Manufacturer Quirks I've Learned
Not all companies size the same way:
- Hunter Douglas: Requires exact recess measurements
- Levolor: Deducts ½" automatically
- Custom Stores: May want both recess and desired size
Always ask "Is this the size I should order or the recess size?" before submitting.
Your Top Questions Answered
Do I measure in inches or centimeters?
Use inches if in the US - most manufacturers work in 1/8" increments. Centimeters often cause rounding errors.
Should blinds cover the entire window?
For inside mount: Yes, they'll be slightly smaller than recess. For outside mount: Extend beyond the glass for best light control.
How important is the 1/2 inch deduction?
Critical! I tried ignoring it once - blinds jammed constantly. This space allows for brackets and smooth operation.
Can I install blinds myself?
Absolutely. Most take under 30 minutes with basic tools. I've done 12 windows in one weekend. Hardest part is getting measurements right for window shades and blinds.
Measurement Checklist Before Ordering
Run through this list (I keep copies in my toolbox):
- □ Measured width in 3 places?
- □ Measured height in 3 places?
- □ Used smallest measurements?
- □ Noted obstructions (handles, cranks)?
- □ Confirmed mounting type?
- □ Checked window depth for inside mounts?
- □ Added overlaps for outside mounts?
- □ Written measurements clearly (window labels help!)
The Golden Rule of Measuring Window Treatments
I'll leave you with what a 30-year installer told me: "Measure like the manufacturer owes you money."
Taking time to understand how to measure for shades and blinds prevents 90% of installation nightmares. Once you nail this, choosing fabrics and styles becomes the fun part!
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