How Do You Accurately Measure for Outside Mount Blinds?

AvatarByAlison Socha Window Coverings

When it comes to enhancing your windows with style and functionality, choosing the right blinds is just the beginning. One popular option that offers a sleek, custom look is outside mount blinds. But before you can enjoy the perfect fit and flawless finish, accurate measurements are essential. Knowing how to measure outside mount blinds correctly ensures that your new window treatments not only complement your space but also operate smoothly and provide the coverage you desire.

Measuring for outside mount blinds involves understanding the dimensions of your window frame and the surrounding wall space, as well as considering factors such as overlap and clearance. This approach differs from inside mount measurements, as the blinds are installed on the wall or molding outside the window opening. Getting these measurements right is crucial to avoid common pitfalls like blinds that are too narrow or too short, which can affect both aesthetics and functionality.

In the following sections, we’ll explore the key steps and tips for measuring outside mount blinds with confidence. Whether you’re a seasoned DIYer or a first-time buyer, mastering this skill will help you achieve a polished look and a perfect fit for your window treatments.

Measuring Width for Outside Mount Blinds

When measuring the width for outside mount blinds, accuracy is crucial to ensure full coverage and proper fit. Begin by using a steel tape measure for precision. Measure the width of the window frame from the outer edge of one side trim to the outer edge of the opposite side trim. This dimension determines the overall width of the blinds.

To provide adequate light blockage and privacy, it is recommended to add extra width beyond the window frame. Typically, adding 2 to 3 inches on each side is sufficient. This overlap helps prevent light gaps and accommodates any mounting hardware.

If the window trim is uneven or has protrusions, take multiple width measurements at the top, middle, and bottom of the window. Use the largest measurement to ensure the blinds cover the entire window area without gaps.

Measuring Height for Outside Mount Blinds

Measure the height of the window area where the blinds will be installed. For outside mounts, this means measuring from the top edge of the window frame or desired mounting point down to the bottom edge where the blinds should end. Use a steel tape measure and record the measurement in inches.

It is important to extend the height measurement beyond the window frame by 2 to 3 inches to allow the blinds to fully cover the window and any trim below. This also ensures that the blinds will not leave gaps at the bottom when lowered.

If mounting above the window frame, measure from the mounting surface (wall or molding) to the desired bottom point. Take height measurements at multiple locations—left, center, and right—to account for any uneven surfaces. Use the longest measurement for ordering.

Determining the Mounting Location

The mounting location affects both the measurements and the installation process. Outside mount blinds are typically mounted on the wall or window casing above and outside the window frame. Consider the following when choosing the mounting position:

  • Ensure there is enough clearance for the blinds to hang freely without obstruction from window handles or cranks.
  • Check for any molding or trim that may interfere with mounting brackets.
  • Verify that the mounting surface is flat and sturdy enough to support the weight of the blinds.
  • Confirm that the chosen mounting location complements the room’s aesthetic and provides optimal light control.

Important Measurement Tips and Considerations

Accurate measurements are essential to avoid ordering blinds that are too small or too large. Keep these tips in mind:

  • Always use a steel tape measure for precision.
  • Measure in inches and record each measurement carefully.
  • Avoid rounding measurements; provide exact dimensions.
  • When in doubt, measure twice to confirm accuracy.
  • Note any obstructions or irregularities around the window.
  • Consider the type and style of blinds, as some may require additional clearance.

Sample Measurement Guide

The following table summarizes recommended measurement practices for outside mount blinds:

Measurement Aspect How to Measure Recommended Allowance Notes
Width Measure from outside edge of one window casing to the opposite edge Add 2 to 3 inches per side Ensures full coverage and light blockage
Height Measure from mounting point above window to desired bottom point Add 2 to 3 inches below window frame Prevents gaps at the bottom
Multiple Measurements Measure width and height at multiple points (top, middle, bottom) Use largest measurement Accounts for uneven surfaces
Mounting Surface Check for obstructions and flatness of wall or casing N/A Ensures proper installation

Preparing for Accurate Measurements

Before beginning to measure for outside mount blinds, gather the necessary tools and ensure the measurement area is clear and accessible. Accurate measurements are critical for a proper fit and optimal function of your blinds.

  • Tools Needed: Steel measuring tape (preferably 12 feet), a pencil, paper or digital device for notes, and a step ladder if measuring high windows.
  • Window Surface: Clean the area around the window frame to remove dust or debris that might interfere with precise measuring.
  • Check Surroundings: Confirm there is adequate space around the window for the blinds to extend beyond the window opening as required by outside mount specifications.
  • Note Obstructions: Identify any handles, cranks, or nearby moldings that could affect the blind’s placement or operation.

Measuring Window Width for Outside Mount Blinds

The width measurement is the most important dimension when ordering outside mount blinds. It determines how much the blind will cover horizontally across the window.

Follow these steps to measure width accurately:

  1. Measure the full width of the desired coverage area on the wall outside the window frame.
  2. Take three separate measurements: one at the top, one at the middle, and one at the bottom of the window area.
  3. Record all measurements and use the widest measurement as your final width.

This method ensures the blind fully covers the window, compensating for any slight variations in the window frame or wall.

Measuring Window Height for Outside Mount Blinds

Height measurement determines how far down the blinds will extend, providing complete coverage and light control.

To measure height correctly:

  1. Identify the desired starting point at the top of the blind. This is usually where the mounting brackets will be installed, above the window frame on the wall.
  2. Measure from this top mounting point straight down to the point where you want the blind to end, typically the window sill or slightly below it.
  3. Take three measurements—left side, center, and right side—to account for any inconsistencies in wall or window height.
  4. Use the longest height measurement for ordering to ensure full coverage.

Determining Extension Beyond the Window Frame

Outside mount blinds need to extend beyond the window frame to provide proper light blocking and privacy. The standard recommendation is to add an additional 2 to 3 inches on each side of the window width and 3 to 6 inches above the frame for the height.

Dimension Recommended Extension Purpose
Width 2-3 inches per side Blocks light gaps and enhances privacy
Height 3-6 inches above window frame Allows mounting space and full window coverage

Adjust these extensions based on the specific window casing, molding, or architectural features. For example, wider extensions may be necessary for ornate moldings or deep window frames.

Recording and Verifying Measurements

Accurate documentation and verification are crucial before ordering blinds.

  • Write down all measurements clearly including width and height, noting the units (inches or centimeters).
  • Double-check measurements by re-measuring the window area to confirm accuracy.
  • Label each measurement indicating which part of the window it corresponds to (e.g., top width, bottom height).
  • Consult manufacturer guidelines as some blind types may require specific measurement adjustments.
  • Consider professional measurement if unsure or if the window area has complex features.

Professional Insights on How To Measure Outside Mount Blinds

Linda Martinez (Window Treatment Specialist, HomeStyle Interiors). When measuring for outside mount blinds, accuracy is paramount. Begin by measuring the width of the window frame from the outermost edges, ensuring you include any molding or trim. It’s best to take three width measurements—top, middle, and bottom—and use the largest number to guarantee full coverage. For the height, measure from the top of the window frame down to where you want the blinds to end, often extending several inches below the sill for optimal light control and privacy.

James O’Connor (Senior Design Consultant, Custom Blinds Co.). The key to a perfect outside mount blind installation lies in allowing sufficient overlap beyond the window frame. I recommend adding at least 2 to 3 inches on each side of the window width and extending the length beyond the sill by a similar margin. This ensures no light gaps and provides a clean, finished look. Always use a steel tape measure and record measurements in both inches and fractions for precision.

Dr. Emily Chen (Architectural Engineer, Window Solutions Research Group). From an engineering perspective, outside mount blinds require careful consideration of mounting surface depth and clearance. When measuring, it’s crucial to verify that the mounting area is flat and unobstructed. Measure the depth from the wall to the window frame to ensure the blind’s headrail will fit without interference. Additionally, confirm that the mounting brackets can be securely installed on the chosen surface to maintain structural integrity and long-term durability.

Frequently Asked Questions (FAQs)

What tools do I need to measure for outside mount blinds?
You will need a steel tape measure, a pencil, and a notepad to record your measurements accurately.

Where should I measure for the width of outside mount blinds?
Measure the exact width of the window frame or the area you want to cover, including any molding or trim if you want the blinds to overlap.

How do I measure the height for outside mount blinds?
Measure from the top edge where the blinds will be mounted down to the desired endpoint, typically the window sill or slightly below it.

Should I add extra inches when measuring for outside mount blinds?
Yes, add at least 2 to 3 inches on each side to ensure full coverage and to block light effectively.

Can I use the same measurements for inside mount and outside mount blinds?
No, inside mount blinds require precise window frame measurements, while outside mount blinds need measurements of the area you want to cover, including overlap.

How do I ensure my measurements are accurate for outside mount blinds?
Measure at least twice, record all dimensions clearly, and consider any obstructions or trim that may affect the fit of the blinds.
Measuring for outside mount blinds requires careful attention to detail to ensure a proper fit and optimal functionality. The process involves measuring the width and height of the area outside the window frame where the blinds will be installed, allowing for adequate coverage and overlap. Accurate measurements should be taken at multiple points to account for any irregularities, and the largest measurement should be used to guarantee full window coverage.

It is essential to consider the mounting surface and any obstructions, such as trim or molding, when determining the placement of outside mount blinds. Providing extra width and height beyond the window opening helps to block light effectively and enhances privacy. Additionally, understanding the specific installation requirements of the chosen blind style can influence measurement techniques and final dimensions.

Ultimately, precise measurement is critical to achieving a professional appearance and ensuring the blinds operate smoothly. Taking the time to measure correctly not only prevents costly errors but also contributes to the overall aesthetic and functionality of the window treatment. By following expert guidelines and double-checking measurements, you can confidently select and install outside mount blinds that meet your needs and enhance your space.

Author Profile

Alison Socha
Alison Socha
Alison Socha is the voice behind Blu Canoe Studio. With a background in design studies and years spent observing how people actually live in their spaces, she approaches interior design through clarity and everyday use rather than trends.

Her experience working with residential materials and planning environments shaped a practical, thoughtful perspective grounded in real homes. Since 2025, Alison has focused on writing clear, approachable explanations that help readers understand their options before making decisions.

Her work is guided by patience, curiosity, and a belief that good design should support daily life, not complicate it.