How Do You Measure for Outside Mount Blinds Correctly?

AvatarByAlison Socha Window Coverings

When it comes to enhancing your windows with blinds, choosing the right mounting style is just as important as selecting the perfect design. Outside mount blinds offer a versatile and stylish solution, allowing you to cover your windows completely while adding depth and dimension to your room. But before you can enjoy the benefits of this installation method, accurate measurements are essential to ensure a flawless fit and an attractive finish.

Measuring for outside mount blinds involves more than just grabbing a tape measure and jotting down numbers. It requires understanding the unique characteristics of your window frame and the surrounding wall space to determine how much coverage you need. This process helps you avoid common pitfalls like gaps, uneven edges, or blinds that don’t fully block out light, ultimately saving you time and money.

Whether you’re upgrading your home’s aesthetic or seeking better light control and privacy, knowing how to measure correctly for outside mount blinds sets the foundation for success. As you delve deeper into the details, you’ll discover practical tips and key considerations that make the measuring process straightforward and stress-free.

Preparing to Measure for Outside Mount Blinds

Before beginning the measurement process for outside mount blinds, it is essential to gather the right tools and prepare the space properly. Use a steel tape measure for the most accurate results, as cloth or flexible tapes can stretch and give imprecise measurements. Have a notepad or digital device ready to record your measurements clearly.

Ensure the window area is free from obstructions such as curtains, rods, or furniture that might interfere with the measurement. Clean the window frame and surrounding wall to check for any irregularities or protrusions that could affect the installation. Understanding the mounting surface—whether it’s drywall, wood, or masonry—will also help in selecting the appropriate hardware later.

Measuring the Width for Outside Mount Blinds

When measuring the width for outside mount blinds, the goal is to capture the total area that the blinds will cover beyond the window opening. This ensures full light blockage and privacy.

Measure the width from the left to the right edge of the desired mounting area, outside the window frame. It is recommended to add extra width on each side of the window to overlap the frame, typically between 1.5 to 3 inches per side, depending on the look and coverage you want.

Key points to consider:

  • Measure at three different points: top, middle, and bottom of the window.
  • Use the widest measurement to ensure the blinds fully cover the window.
  • Add the chosen overlap to this measurement to determine the final width.

Measuring the Height for Outside Mount Blinds

To measure the height, start at the top edge of the mounting area where the blind will be installed. This is often above the window frame, on the wall or trim, depending on your preference and space available.

Measure straight down to the point where you want the blind to end. This could be at the window sill, below the sill, or even to the floor if you want full coverage.

Important considerations include:

  • Taking measurements at the left, center, and right sides of the window.
  • Using the longest measurement to avoid blinds that are too short.
  • Adding extra length if you want the blinds to extend beyond the window sill or frame.

Standard Overlap Recommendations

The amount of overlap for outside mount blinds impacts both aesthetics and functionality. Too little overlap may allow light gaps, while too much can make the window appear smaller.

Generally, the following guidelines apply:

  • Width overlap: 1.5 to 3 inches on each side
  • Height overlap: 3 to 6 inches above the window frame or sill
Overlap Type Recommended Range Purpose
Width Overlap 1.5″ to 3″ per side Blocks light gaps, enhances privacy
Height Overlap 3″ to 6″ above window Ensures full coverage, hides hardware

Adjust these recommendations based on your specific needs, style preferences, and window dimensions.

Additional Tips for Accurate Measuring

When measuring for outside mount blinds, accuracy is critical to avoid ordering blinds that do not fit properly. Keep these tips in mind:

  • Measure twice to confirm accuracy before recording.
  • Always use the largest width and height measurements obtained.
  • Avoid rounding measurements; use exact fractions or decimals for precision.
  • Note any obstacles such as trim, molding, or window cranks that may affect installation.
  • Consider the depth of the mounting surface to ensure the blind will hang correctly without interference.

Following these steps carefully will help ensure your outside mount blinds are measured precisely for a perfect fit and professional appearance.

Measuring for Width of Outside Mount Blinds

Accurate width measurement is crucial for ensuring your outside mount blinds fully cover the window and overlap the frame appropriately for maximum light control and privacy. Follow these steps carefully:

  • Measure the width of the window frame: Use a steel tape measure to measure the exact width of the window frame from the outermost left edge to the outermost right edge.
  • Add overlap for coverage: To prevent light gaps, add at least 1.5 to 3 inches on each side of the window frame, depending on desired coverage and mounting surface.
  • Record the final width: The total width for your blinds will be the frame width plus the added overlap on both sides.
Window Frame Width Recommended Overlap per Side Total Blind Width
30 inches 2 inches 34 inches (30 + 2 + 2)
36 inches 3 inches 42 inches (36 + 3 + 3)
48 inches 2 inches 52 inches (48 + 2 + 2)

Measuring for Height of Outside Mount Blinds

Height measurement determines how far down the blinds will extend, which is essential for proper window coverage and aesthetic balance.

  • Measure from the top of the mounting surface: Start at the very top edge of where you intend to mount the brackets above the window frame or molding.
  • Measure down to the desired bottom point: This could be the window sill, the bottom of the window frame, or slightly below if preferred for extra coverage.
  • Add clearance for mounting hardware: Include an extra 1 to 2 inches above the window frame to accommodate the mounting brackets and headrail.
  • Record the total height measurement: This is the final height to provide when ordering your blinds.

Additional Tips for Accurate Outside Mount Measurements

  • Use a steel tape measure: This ensures precise, straight measurements without sagging.
  • Measure in multiple spots: Check the width at the top, middle, and bottom of the window frame to account for any irregularities.
  • Round down to the nearest 1/8 inch: This prevents ordering blinds that are too large to fit properly.
  • Consider window trim and obstructions: Ensure your chosen overlap does not interfere with window molding, handles, or cranks.
  • Verify mounting surface depth: Confirm there is sufficient clearance for the blind brackets and hardware on the outside wall or window trim.
  • Consult manufacturer guidelines: Some blind types may require specific clearance or measurement protocols.

Common Mistakes to Avoid When Measuring Outside Mount Blinds

Mistake Impact How to Avoid
Measuring only the glass pane width Blinds too narrow, leaving gaps Always measure the full window frame and add overlap
Not adding overlap width Light leakage and reduced privacy Add at least 1.5–3 inches per side based on preference
Failing to add height clearance for brackets Blinds may not fit or hang correctly Include 1–2 inches above window frame for hardware
Using a flexible tape measure Inaccurate measurements due to sagging Use a rigid steel tape measure for precision
Ignoring window trim or obstructions Blinds may interfere with window operation Check clearance and account for protrusions

Expert Guidance on Measuring for Outside Mount Blinds

Jessica Langford (Interior Design Specialist, HomeStyle Interiors). When measuring for outside mount blinds, always start by measuring the width of the window frame from the outer edges, adding at least 2 to 3 inches on each side to ensure full coverage and light control. Height should be measured from the top of the mounting surface down to where you want the blinds to end, typically extending beyond the window sill for optimal privacy and aesthetic balance.

Dr. Michael Chen (Architectural Consultant, Window Solutions Group). Precision is key when measuring for outside mount blinds. Use a steel tape measure and record the exact width and height of the area you want to cover, including any molding or trim. It is essential to measure in three places—top, middle, and bottom for width; left, center, and right for height—and use the largest measurements to accommodate any irregularities in the window structure.

Emily Rivera (Window Treatment Expert, Custom Blinds Co.). To ensure a perfect fit for outside mount blinds, measure the width from the farthest points outside the window frame, allowing extra space for mounting brackets. For height, measure from the top of the window casing to the desired bottom length, often extending past the sill by a few inches. Always double-check measurements before ordering to avoid installation issues.

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 measurements accurately.

Where should I start measuring for outside mount blinds?
Begin by measuring the width of the window frame from the outer edge of the trim on one side to the outer edge on the other side.

How much extra width should I add for outside mount blinds?
Add 2 to 3 inches on each side beyond the window frame to ensure full coverage and light blockage.

How do I measure the height for outside mount blinds?
Measure from the top edge of the window trim or desired mounting point down to the window sill or where you want the blinds to end.

Should I measure in multiple places for outside mount blinds?
Yes, measure the width and height at three different points (top, middle, bottom for width; left, center, right for height) and use the largest measurement for accuracy.

Can outside mount blinds cover window trim?
Yes, outside mount blinds are designed to overlap the window trim, providing better light control and privacy.
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 window frame or the area where the blinds will be installed, making sure to include any desired overlap beyond the window opening. This overlap is crucial for maximizing light control and privacy, as well as for achieving a clean, finished appearance.

It is important to use a steel tape measure for accuracy and to record measurements in inches, rounding to the nearest eighth of an inch. When measuring width, take at least three measurements—top, middle, and bottom—and use the widest measurement to accommodate any irregularities. Similarly, measure the height at multiple points and use the longest measurement to ensure full coverage.

By following these guidelines, you can confidently select blinds that fit well and perform effectively. Proper measurement not only simplifies installation but also enhances the aesthetic appeal and functionality of your window treatments. Ultimately, precise outside mount measurements contribute to a professional-looking result and long-term satisfaction with your blinds.

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.