How to Measure for Blinds? Step-by-Step Guide
May 15, 2025
Key Notes
Inside-mount measurements require precise width and height at three different points for each window.
Outside-mount measurements need additional overlap for optimal light blocking and privacy protection.
Measure each window individually, as homes often have subtle variations between seemingly identical openings.
Record all measurements in decimal inches (not fractions) with width always listed first.
The Basics: Tools and Techniques
Accurate measurements are the foundation of perfectly fitting blinds.
While the process may seem straightforward, even small measurement errors can lead to ill-fitting window treatments that compromise both functionality and appearance.
In homes where protection from intense sunlight is crucial, properly measured blinds make all the difference in comfort, energy efficiency, and style.
Tools You Need for Accurate Measurements
Successful blind measurement begins with the right tools and a clear understanding of mounting options. This foundation ensures precision throughout the process.
You'll need:
Steel measuring tape for consistent readings
Step stool for reaching tall windows safely
Notepad to record measurements
Pencil for marking measurement points
Level to check for uneven surfaces
Consider investing in a laser measuring tool for high or difficult-to-reach windows. These tools provide precise measurements without requiring ladder work in challenging spots.
Step-by-Step Measurement Guide
Inside Mount Measurement Techniques
For inside mounts, you'll measure the exact window opening where the blinds will sit.
Follow these steps for precision:
Measure width at three points: Take measurements at the top, middle, and bottom of the window opening.
Record the narrowest measurement: Blinds must fit within the smallest width to avoid scraping against the sides.
Measure height at three points: Measure from the top inside edge to the windowsill at the left, center, and right sides.
Record the shortest measurement: This ensures your blinds won't hit the bottom when fully extended.
Check depth: Measure the depth of your window frame from the glass to the edge of the frame. Most blinds require at least 2 inches of depth for proper installation.
Outside Mount Measurement Techniques
For outside mounts, you'll measure the area you want the blinds to cover rather than the window opening itself:
Determine desired width: Measure the width of the window opening, then add at least 2 inches on each side (4 inches total) for optimal light blocking and privacy.
Determine desired height: For windows with sills, measure from where you want the blinds to start (typically 3 inches above the window) to the sill. For windows without sills, add 3-4 inches below the window opening.
Consider overlapping requirements: For maximum light control – especially important in bright Florida conditions – plan for blinds to extend 3-4 inches beyond the window opening on all sides.
Verify mounting surface: Ensure you have enough flat surface area for brackets, typically at least 2 inches above the window and on each side.
Addressing Common Challenges
Even the most seemingly straightforward windows can present measurement challenges.
Here's how to handle common issues:
Handling Uneven Windows
Many homes, especially older ones, have windows that aren't perfectly square. Here's how to address this challenge:
Check for squareness: Measure diagonally from corner to corner in both directions. If these measurements differ by more than 1/4 inch, your window isn't square.
Use the smallest measurements: For uneven windows, always use the smallest width and height measurements to ensure proper operation.
Consider outside mounts: For significantly uneven windows, outside mounts often provide better results as they don't rely on the window frame for alignment.
Use shims during installation: Note areas of unevenness so you can use shims during installation to create a level mounting surface.
Measuring Specialty Window Shapes
Arched, circular, and triangular windows require specialized approaches:
For arched windows:
Measure the width at the base of the arch
Measure the height from the base to the highest point
For half-circles, measure the radius from the center of the base to the highest point
For circular windows:
Measure the diameter at several points through the center
Use the smallest measurement to ensure proper fit
For triangular windows:
Measure all three sides
Measure the height from the base to the apex
Note the angle of each corner
For these specialty shapes, consider consulting with window treatment professionals who can provide templates and custom solutions.
Advanced Considerations for Modern Blinds
Integrating Smart Home Technology
Motorized blinds require special measurement considerations:
Power source planning: Determine whether your motorized blinds will be hardwired, battery-operated, or solar-powered, as this affects mounting depth requirements.
Clearance for components: Allow additional space for motors and other mechanical components, typically requiring at least 3 inches of mounting depth for inside mounts.
Wiring considerations: For hardwired options, plan pathways for electrical connections and ensure measurements account for these routes.
Group operation planning: If controlling multiple blinds with one motor, measure to ensure all windows in the group have identical dimensions.
One Wrong Number Could Throw The Whole Thing Off
We’ll handle the measuring, so your blinds fit like they should
Frequently Asked Questions
How much additional overlap should I add for outside-mount window treatments?
For optimal light blocking and privacy, add 1.5-2 inches of overlap on each side and 3-4 inches at the top and bottom of your window opening.
What tools do I need for accurate window measurements?
At minimum, you'll need a metal measuring tape (not cloth or plastic), a pencil, and paper. A level can also be helpful to check if your window frames are square.
My windows have unusual features like rounded tops or divided panes. How do I measure these?
For specialty windows, measure the widest and tallest points of the opening. For arched or rounded windows, measure the full height to the highest point and note the window shape when ordering. Many manufacturers offer templates for specialty shapes.
How do I account for window sills when measuring for treatments like roman shades or blinds?
For inside mounts, measure from the top of the window opening to the sill. For outside mounts that will extend beyond the sill, ensure there's enough clearance for the treatment to operate properly without obstruction.
Conclusion
There’s a lot riding on getting those numbers right, especially if you’re aiming for blinds that actually sit flush, block the light properly, and don’t catch every time they’re raised or lowered.
Even small things, like uneven frames or shallow mounting depths, can throw the whole thing off. And while the measuring process isn’t hard, it does ask for precision and a bit of patience.
If you’d rather have someone handle it who knows the quirks of Florida homes – and can spot the issues before they become problems – you can book a free appointment with our team. We’ll measure everything properly, bring samples to compare, and make sure your window treatments look as good as they function.
