How to Measure for Vertical Blinds for Sliding Glass Doors: The Foolproof Guide

The Challenge of the Sliding Door

Sliding glass doors (patio doors) are the trickiest part of the house to cover. They are high-traffic areas, they are huge, and they have protruding handles that ruin standard installations.

Whether you are replacing broken 90s-style vertical blinds or upgrading to a modern solution, precision is everything. A mistake of just half an inch can mean your blinds drag on the floor or get stuck on the door handle.

Grab your steel tape measure (never use cloth tape!), a pencil, and paper. Here is the professional way to measure for a sliding glass door.

Decision 1: Inside Mount vs. Outside Mount

Before you measure, you must decide how you want to hang them.

Option A: Inside Mount (The Clean Look)

The headrail fits inside the window frame (recess).

Pros: Looks built-in and tidy.
Cons: Rarely works for sliding doors. Why? Because most sliding glass doors don’t have enough “depth” in the frame to hold the blind and clear the door handle.
Requirement: You typically need at least 3-4 inches of clear window depth past the handle.

Option B: Outside Mount (The Standard Choice)

The headrail is mounted on the wall above the door frame or on the trim (architrave).

Pros: Clears the door handle easily; blocks more light; makes the door look wider.
Cons: The hardware is visible (unless you have a valance).
Verdict: 95% of sliding door installations are Outside Mounts.

How to Measure for an OUTSIDE Mount (Recommended)

Since most homeowners choose this for sliding doors, we will start here.

Step 1: Measure the Width

You aren’t just covering the glass; you want to cover the frame for privacy.

Measure the width of the door frame from outer edge to outer edge.
The “Privacy Add-On”: Add 4 to 6 inches to your total measurement (2-3 inches per side). This overlap ensures that when the sun hits the side, light doesn’t leak in, and people can’t peek through the edges.
- Example: If the frame is 70″, order a 74″ or 76″ width.

Step 2: Measure the Height

This is critical. You don’t want the vanes dragging on the floor and collecting dust.

Decide where you will mount the headrail (usually 2-3 inches above the door frame for structural support).
Measure from that spot down to the floor.
The “Clearance Deduction”: Deduct 0.5 inch (or 1 inch if you have thick carpet) from the total height.
- Why? Vertical blinds stretch slightly over time. You want them to “float” just above the floor.

Step 3: The “Handle Check” (Don’t Skip This!)

This is the #1 mistake DIYers make.

Measure how far your door handle sticks out from the wall (projection).
Ensure your mounting brackets (spacer blocks) extend further than the handle. If your handle sticks out 2 inches, but the blind hangs at 1.5 inches, it will hit the handle every time you close it.

How to Measure for an INSIDE Mount

If you are lucky enough to have a deep recess (drywall returns) and no obstructing handle:

Step 1: Measure the Width (3 Places)

Measure the inside width at the Top, Middle, and Bottom.

Record the Narrowest measurement.
Why? If your frame is slightly bowed, the blind needs to fit the tightest point, or it will jam.

Step 2: Measure the Height (3 Places)

Measure the inside height at the Left, Center, and Right.

Record the Shortest measurement.
Why? If you use the tallest height, the blind will drag on the floor at the shorter end.

Step 3: Check the Depth

Measure the depth of the top casing. Compare this to the manufacturer’s “Minimum Flush Mount Depth” requirement.

A Modern Alternative?

While you are measuring for vertical blinds, ask yourself: Do I really want slats again?

Vertical blinds are functional, but they can be noisy and notoriously hard to clean. Many modern homeowners are switching to Large-Format Roller Shades or Sliding Panels for patio doors.

Roller Shades: Can be installed as two separate shades (split) for versatile control.
LazBlinds Advantage: Our custom-cut roller shades offer a sleeker, slat-free look that fits modern interiors perfectly.

Have your measurements ready? Whether you choose vertical or roller, precision is key. Shop Our Custom Patio Door Solutions

The Challenge of the Sliding Door