Wondering how to measure for Vertical Blinds so you get a flawless fit the first time? Avoiding common measuring mistakes is key to achieving a polished look and smooth installation. Here are some quick tips on how to measure.

To measure for vertical blinds, start by choosing your mount type: inside or outside. For an inside mount, where blinds fit within the window frame, measure the width in at least 3 places, and use the smallest width. Measure height also in at least 3 places and use the tallest height. For an outside mount, where blinds are installed above or on the wall surrounding the frame, measure the total area you want covered and add 2–3 inches to both width and height for overlap. Always record measurements to the nearest 1/8 inch for the most accurate fit.

1. Gather Necessary Tools

Before you start, make sure you have everything you need for accurate, reliable measurements. Precision is key to a perfect fit, even small errors can affect how your blinds look and operate.

• Steel tape measure – Essential for accuracy; avoid cloth or plastic tapes, as they can stretch and throw off your results.

• Pencil and notepad – Record each number carefully and double-check your entries.

• Good lighting – Bright, even light helps ensure you read and mark measurements correctly.

• Clear workspace – Remove clutter and obstacles so you can measure without interference or mistakes.

• Ladder or step stool (if necessary) – Provides safe access to tall or hard-to-reach windows for accurate measurements.

2. Consider Inside or Outside Mount

Choosing between an inside or outside mount affects both the look and function of your blinds.

Inside mounts offer a clean, built-in appearance and work best if your window frame is deep enough. Outside mounts can make windows appear larger and are ideal for shallow frames or to cover unattractive trim. For wide openings such as sliding glass doors or patio doors, an outside mount is often recommended to ensure full coverage and smooth operation.

Your choice will determine where you start and end your measurements, so decide before you begin.

Pros and Cons: Inside Mount Verses Outside Mount

Inside Mount

Pros:

• Sleek, custom look – fits neatly within the frame for a clean appearance.

• Preserves window trim – keeps molding and casing visible.

• Ideal for layered treatments – pairs well with drapery or valances.

• Better light control – provides a tight, built-in fit.

Cons:

• Requires sufficient window depth – needs enough recess for headrail and vanes. 

• May allow small light gaps – minimal spacing at edges can let in light.

• Highlights uneven frames – imperfections are more visible with inside mounts.

Outside Mount

Pros:

• Makes windows appear larger – adds visual height and width to small openings.

• Hides imperfections or trim – conceals uneven surfaces or unattractive frames.

• Flexible for shallow frames – ideal when there isn’t enough depth for an inside mount.
  Maximizes privacy and light blockage – overlaps the window for full coverage.

Cons:

• Covers some wall space – requires additional width and height beyond the frame.

• May interfere with nearby moldings or fixtures – ensure enough clearance before installing.

• Less built-in appearance – sits outside the window recess for a more prominent profile.

Additional Considerations

When deciding on an inside or outside mount, consider factors like stack width, clearance, and surrounding obstacles to ensure your blinds fit and function perfectly.

• Plan for stack width: Vertical blinds stack to one side (or both, for split stacks) when fully open, meaning part of the window will remain covered in an inside mount, but may be accounted for with an outside mount.

• A 3½″ vane blind typically stacks about 7–8 inches on a 40″ window and 25–30 inches on a 160″ window. These measurements are approximations and may vary depending on design choices.

• Add extra width: Include 2–3 inches of overlap on each side to help the vanes clear the window or door completely and improve light control.

• Check for obstacles: Look for trim, handles, or moldings that might interfere with headrail placement or vane movement.

• For sliding glass doors: Position the stack on the opposite side of the active door panel to keep pathways open and maintain your view.

3. Measure Window Width

If you're wondering where to start measuring for vertical blinds, start by determining the width of your window.

For inside mounts, measure inside the window frame at the top, middle, and bottom, and record the narrowest width for the most accurate fit.

4. Measure Window Height

While all measurements matter, height is especially important to ensure your vertical blinds provide full coverage and a precise fit. Accurate height measurements should account not only for the window opening, but also for the headrail height and the small gap between the vanes and headrail, which together determine the total hanging length (or drop) of your blinds.

For inside mounts, measure from the top inside edge of the frame down to the sill in three places: left, center, and right. Use the longest measurement to ensure full coverage.

5. Double Check Measurements

Double-Check or Let Us Handle It: 3 Day Blinds provides free in-home measuring and professional installation, ensuring a perfect fit every time.

Accuracy is everything. Double check each measurement and record them clearly. Organize your notes by window and room to avoid confusion. When you’re ready to order, communicate your measurements exactly as taken to your design consultant, don’t make deductions or additions unless instructed. At 3 Day Blinds, your design consultant will confirm all measurements during your free in-home consultation, ensuring a perfect fit.

6. Common Mistakes When Measuring for Vertical Blinds

Avoid these common measuring errors to ensure a perfect fit and professional finish:

1. Skipping the mount decision - Failing to choose between an inside or outside mount before measuring leads to incorrect dimensions and fitting issues.

2. Using the wrong tape measure - Cloth or plastic tape measures can stretch and cause inaccuracies. Always use a steel tape measure for precise results.

3. Rounding measurements - Never round up or down. Record all measurements to the nearest ⅛ inch for accuracy.

4. Ignoring window frame depth - Insufficient depth may prevent proper inside mounting. Verify that your frame meets the minimum depth requirement for your vane size.

5. Forgetting stack width - Overlooking how much space the vanes occupy when open can block part of your view or door. Always factor in stack width in your total measurement.

6. Not checking for obstacles - Trim, handles, or nearby fixtures can interfere with headrail installation. Clear and measure the space carefully.

7. Mixing width and height values - Label and organize measurements by window and direction to prevent mix-ups when ordering.

8. Ignoring professional help - Measuring seems simple, but minor errors can lead to costly reorders. 3 Day Blinds Design Consultants provide free professional measuring, ensuring a perfect fit the first time.

7. Order Your Vertical Blinds

Once your measurements are finalized, your 3 Day Blinds design consultant will do the proper deductions and review with you the product's design considerations, ensuring your custom-made blinds will be crafted to your specifications. With 3 Day Blinds, you’ll receive a no-obligation, same-day quote from your Design Consultant, who will expertly coordinate the installation process to ensure a seamless experience.

8. Professional vs. DIY Installation

Instead of tackling the complexities of installation yourself, allow our professionals to manage the process for you. Our team ensures your blinds are measured and installed precisely, enhancing your home's style and functionality.

When you choose 3 Day Blinds, you get more than just installation:

• Limited Lifetime Warranty – Enjoy peace of mind knowing your custom blinds are backed by long-term protection.

• Fully Custom Designs – You choose the type, color, vane size, material, and valance style to match your décor perfectly.

• Fast Turnaround Times – From consultation to installation, our streamlined process brings your vision to life quickly.

9. Enjoy Your New Blinds!

With your new vertical blinds installed by our experts, enjoy the enhanced style, privacy, and light control they bring to your home, and take pride in the beautiful transformation of your space.

To keep your blinds looking their best for years to come, check out our guide on how to clean window coverings for easy care tips and maintenance recommendations.

3 Day Blinds provides professional measuring and installation services nationwide, bringing expertise and convenience right to your door.