How to Measure for Custom Blinds: Edmonton DIY Step-by-Step Guide (2026)

Measuring for custom blinds looks simple until you end up with a shade that’s 3/8″ too short and a refund conversation you didn’t want to have. The good news: with a steel tape, 10 minutes per window, and the checklist below, you can measure your whole home accurately enough for a quote — and accurately enough to order directly if you’re confident. This is the step-by-step guide we give Edmonton homeowners who want to DIY the measure before a consultation, or who are ordering online and want to get it right the first time. We’ll cover inside mount, outside mount, depth, the weird windows (bays, arches, french doors), and the mistakes that cost people money.

Before You Start: What You’ll Need

• A steel measuring tape — not a cloth or plastic one. Cloth stretches; steel doesn’t. A 25-foot tape is ideal; 16-foot works for standard windows.
• A pencil and a notepad (or your phone’s notes app). Write measurements down immediately — don’t rely on memory across 10 windows.
• A stepladder for tall windows. Measuring tall windows from the floor with a flex tape is how mistakes happen.
• A helper (optional but recommended for windows over 48″ wide). Holding a steel tape taut across a 60″ window is harder than it sounds.
• A small flashlight for checking window frame depth and obstructions.

One thing you do not need: precision tools, lasers, or anything fancy. A decent steel tape and careful attention to detail is all any professional installer actually uses.

Step 1: Decide Inside Mount or Outside Mount

This is the first decision and it changes everything about how you measure.

Inside mount

The blind sits inside the window frame, flush against the glass side. This is the cleaner, more built-in look and works on most modern windows. You need at least 2″ of usable depth inside the frame for most roller and cellular shades, and 3″+ for zebra blinds or shades with side tracks. Measure the depth carefully — if your window has cranks, latches, or tilt-out hardware, those eat into your usable depth.

Outside mount

The blind mounts on the wall above and extends past the window opening on both sides. Use outside mount when: (1) your window frame is too shallow for inside mount, (2) you want maximum light blocking (outside mount is the go-to for blackout bedrooms because it seals the edges), (3) the window is a weird shape or has visible damage to the frame you want to hide, or (4) you want the window to look larger than it is. Quick rule: if you want the “clean modern” look and the frame is deep enough, go inside mount. If you want maximum blackout or need to hide something, go outside mount. For most bedroom blackout setups, outside mount is our default recommendation.

Step 2: Inside Mount Measurements (The 3-3-1 Method)

For every inside mount window, you take three widths, three heights, and one depth. Here’s why: window openings are rarely perfectly square. A new construction frame might be 1/4″ wider at the bottom than the top, or an older home might be off by 1/2″ or more. Measuring at multiple points catches this.

Measure width at three points:

1. Top width: inside-frame-to-inside-frame, at the very top of the window opening.
2. Middle width: same measurement, at mid-height.
3. Bottom width: same, at the very bottom.

For your order width, use the narrowest of the three. The factory will cut to your number exactly — if you give them the widest measurement and the frame narrows elsewhere, the blind won’t fit.

Measure height at three points:

1. Left height: inside-frame-top to inside-frame-bottom (or windowsill), on the left side.
2. Middle height: same, down the middle.
3. Right height: same, on the right side.

For your order height, use the tallest of the three (so the blind reaches the sill all the way across). The exception: if you don’t want the blind to touch the sill at all, order the shortest measurement minus 1/2″.

Measure depth once:

From the wall plane (where the blind bracket will mount) to the innermost obstruction — usually the glass itself, or a crank, latch, or tilt-out handle. Record the depth and note what limits it. Your fabricator needs to know if there’s a crank at 1-1/2″ deep or just clear glass at 4″.

Record measurements as width × height

Always width first, then height. So “36-1/4 × 58” means 36-1/4 inches wide, 58 inches tall. Getting this backwards is the single most common ordering mistake and it’s embarrassing for everyone involved.

Step 3: Outside Mount Measurements

Outside mount is more forgiving because you’re the one choosing how much the blind extends past the window. A few principles:

• Extend at least 2″ past the opening on each side for good light-gap coverage. For blackout bedrooms, extend 3″+ on each side.
• Mount the bracket at least 2″ above the opening (3″+ is better) so the blind hardware doesn’t sit right on top of the window trim. This looks cleaner and lets you raise the blind fully above the opening.
• For the height, measure from the bracket location down to where you want the blind to end — typically 1-2″ below the sill, or all the way to the floor for drapery-style drops.

Write down the finished width you want (not the window opening width) and the finished height you want. Your fabricator orders to those numbers.

Step 4: Double-Check Depth (Inside Mount Only)

This is where most DIY measurements go wrong. Depth determines which products can even fit in your window. Here’s what different products need:

• Roller shades: 1-1/2″ minimum depth for standard roller tube, 2″ for larger tubes (larger blinds).
• Single cell cellular shades: 1-1/2″ minimum depth.
• Double cell cellular shades: 2″ minimum depth.
• Zebra blinds: 2-1/2″+ depth (zebra has a thicker cassette than roller).
• Cellular with side tracks: 3″+ depth.
• Horizontal 2″ faux wood blinds: 2-1/2″+ depth.
• Motorized anything: typically 2-1/2″+ depth to fit the motor tube.

If your depth is under the minimum, you can still do inside mount with a “partial inside mount” (the blind hangs slightly proud of the frame) or switch to outside mount.

Step 5: Write Everything Down in a Consistent Format

Here’s the format we use and recommend:

Window ID | Room | Mount | Width (in) | Height (in) | Depth (in) | Notes
W1 | Primary bedroom | Inside | 36-1/4 | 58 | 3-1/2 clear | 3 widths matched within 1/8
W2 | Primary bedroom | Inside | 36-1/8 | 58 | 3-1/2 clear | Matched W1
W3 | Kitchen over sink | Outside | 48 | 42 | n/a | Extend 3 past, 3 above
W4 | Living room | Inside | 71-1/2 | 60 | 2 (crank) | Narrowest at bottom

A spreadsheet or simple notepad list works. The key is making sure every window has: room, mount type, width, height, depth, and notes about any obstructions or irregularities. If you’re sending this to us for a quote, this format saves a follow-up call.

Special Cases: The Tricky Windows

Bay windows (3 windows, often at 135° or 90° angles)

Measure each of the three windows independently — same 3-3-1 method for each. Note the angle between the windows (most Edmonton bays are 135°, but some new builds use 90° or even 120°). You’ll end up with three separate blinds, not one; the angles matter for where the blinds meet at each corner. Sketch the top-down view if you can.

Arched or rounded-top windows

Measure the widest point and the tallest point. For arched windows, you’ll also need a few “spring points” along the curve — we usually ask homeowners to take a photo with a tape held vertically at the peak and we’ll handle the pattern. DIY arched measuring is hard; if you have several arches, book a consultation.

French doors

Each door gets its own blind, typically inside mount to the door panel itself (not the door frame). Depth is usually tight on french doors (1-1/2″ or less). Also measure the handle position — many french-door blinds need to accommodate a door knob or lever. Specialized hold-down brackets keep the blind from swinging when the door moves.

Sliding patio doors

Measure the full opening (door frame inside-to-inside) in width and height. For vertical blinds or a panel track system, the blind runs outside mount above the door frame. Measure from 3″ above the door frame to the floor or the height you want; add 3-4″ to the opening width on each side for light-gap coverage.

Skylights and cathedral windows

Don’t DIY these. Book a measure. The pricing is different, the mounting is specialized, and a bad measurement on a ceiling window is much harder to fix than on a wall window.

The Most Common Mistakes (And How to Avoid Them)

1. Using a cloth measuring tape. Cloth stretches. A 60″ measurement can read 59-3/4″ to 60-1/4″ depending on how taut you pull. Use steel.
2. Rounding to the nearest half-inch. Measure to 1/8″ precision. 36-1/4″ is not the same as 36-1/2″ to a blind factory — that 1/4″ can be the difference between fitting and not.
3. Measuring over existing blinds or drapes. Remove the old window covering first. Existing brackets can block accurate inside-frame measurements by 1/4-1/2″.
4. Only measuring once. Always three widths, three heights for inside mount. Frames are rarely square.
5. Forgetting depth. Depth determines which products can even be used. Record it for every inside-mount window.
6. Mixing up width and height. Width first, always. If you’re unsure, write “W” and “H” next to each number.
7. Not noting obstructions. A window crank at 1-1/2″ depth kills most inside-mount options. Note it.

When to Skip the DIY Measure and Book a Pro

DIY measuring works great for 90% of standard Edmonton windows. Skip it and call us if:

• You have arched, circular, or oddly-shaped windows.
• You have 10+ windows and want a single cohesive quote with professional measurement guarantee.
• Your windows are in a heritage home with frames that are visibly out of square (more than 1/2″ variation).
• You’re doing skylights, cathedral windows, or anything above 10 feet off the floor.
• You want warranty coverage on fit — most of our custom products carry a measurement guarantee only when we measure. DIY measurements are your responsibility.

For context on full-home pricing with pro measurement included, see our Edmonton custom blinds cost guide.

Quick Reference: Measuring Checklist

1. Pick mount type (inside or outside)
2. Steel tape, notepad, flashlight ready
3. For inside mount: 3 widths, 3 heights, 1 depth per window
4. Take narrowest width, tallest height for inside mount orders
5. Record to 1/8″ precision, width × height, with mount type and notes
6. Double-check depth against product minimums before ordering
7. Sketch or photo any unusual windows

Ready for Accurate Quotes?

If you’ve measured your home and want a written quote, send us your list — room, mount type, dimensions, and a photo if anything is unusual. We’ll quote within 48 hours. If you’d rather have us measure, we offer free in-home consultation across Edmonton and area with measurement guarantee on any order. Book a consultation or send your measurements directly.

Frequently Asked Questions

How accurately do I need to measure for custom blinds?

To 1/8″ precision. Blind factories cut to your exact numbers, so a 1/4″ rounding error can mean a blind that doesn’t fit. Use a steel measuring tape (not cloth or plastic), measure three times at different points, and record every measurement to the nearest 1/8″.

Should I measure for inside mount or outside mount?

Inside mount if your window frame has at least 2″ of depth and you want a clean built-in look. Outside mount if your frame is shallow, you want maximum blackout coverage (especially in bedrooms), or you want to make the window look larger. For most bedrooms we recommend outside mount; for most living rooms, inside mount.

What’s the minimum depth needed for inside-mount blinds?

Single cell cellular shades and basic roller shades need 1-1/2″ minimum depth. Double cell cellular shades and 2″ faux wood horizontal blinds need 2″ to 2-1/2″. Zebra blinds need 2-1/2″+. Motorized products typically need 2-1/2″+ to accommodate the motor tube. Cellular with side tracks needs 3″+. Measure before choosing the product.

How do I measure a bay window for blinds?

Treat it as three separate windows, each with its own independent measurement (three widths, three heights, one depth each). Also note the angle between the bay windows — most Edmonton bays are 135° but some newer builds use 90° or 120°. You’ll order three blinds total, not one, and the angles affect how they meet at each corner.

Do I measure the opening or the finished blind size?

For inside mount: measure the window opening exactly — the factory accounts for the deduction needed to fit the blind inside. For outside mount: measure the finished size you want the blind to be (including the extension past the window on each side), because the factory builds to your stated dimensions.

Can I measure windows myself or should I have a professional do it?

DIY measuring works well for standard rectangular Edmonton windows — just follow the 3-3-1 method with a steel tape. Skip the DIY and book a pro measure for arched windows, skylights, cathedral windows, or any window over 10 feet off the floor. Also consider a pro measure on whole-home orders where measurement guarantee coverage matters.