Ordering new window treatments transforms a room, adding privacy, light control, and serious style. However, achieving that flawless designer look all comes down to a crucial first step: taking accurate measurements. When you learn how to measure windows properly, you guarantee a smooth installation and a beautiful final result.
Custom blinds are built specifically to your exact specifications. Unlike off-the-shelf options, there is no wiggle room for error. A fraction of an inch can mean the difference between a perfect fit and blinds that scrape against the window frame or let in unwanted light.
This guide walks you through the entire process. We cover the essential tools you need, the exact steps for both inside and outside mount blinds, and expert tricks to get perfect measurements the very first time.
Essential Tools Required for Measuring Windows
Before you approach your window, gather the right equipment. Using the correct tools makes the job easier and prevents costly measurement mistakes.
- Steel Measuring Tape: Never use a cloth tape measure or a wooden yardstick. Cloth stretches over time, and yardsticks cannot fit snugly into window corners. A standard steel tape measure provides the rigidity and precision required for custom window treatments.
- Notepad and Pencil: Have a dedicated piece of paper ready. You need to write down every measurement immediately to avoid memory errors. Always use a pencil so you can easily correct mistakes.
- Step Ladder: For taller windows, use a sturdy step ladder. Stretching or guessing measurements from the floor leads to inaccurate numbers.
- Carpenter’s Level: This helps you check if your window frame is perfectly straight, which is especially important for older homes where windows might have settled.
Step-by-Step Instructions: Measuring Inside Mount Blinds
Inside mount blinds sit entirely within the window frame. They provide a clean, modern look and highlight your window’s decorative molding. Because they sit inside the opening, precision is critical.
Step 1: Check Window Depth and Squareness
First, ensure your window frame has enough depth to accommodate the mounting brackets. Measure from the front of the window frame back to the glass. If your window lacks the minimum depth required by the manufacturer, the blinds will protrude.
Next, check for “squareness” by measuring the window diagonally from corner to corner in both directions. If the two diagonal measurements differ significantly, your window is not square. In this case, an outside mount might be a better option.
Step 2: Measure the Width
Measure the inside width of the window frame in three distinct places. Measure straight across the top, the middle, and the bottom. Write down all three numbers. For inside mount blinds, always use the narrowest measurement. The factory will make the necessary deductions to ensure the blinds do not rub against the sides of your window.
Step 3: Measure the Height
Measure the inside height of the window frame in three places as well. Measure from the top inside edge down to the window sill on the far left, the center, and the far right. Record all three measurements. For most inside mount blinds, you use the longest measurement.
Step-by-Step Instructions: Measuring Outside Mount Blinds
Outside mount blinds attach directly to the wall or molding above the window. This mounting style makes a window appear larger, blocks more light, and hides unattractive window frames. Since these blinds sit entirely outside the opening, the measuring process focuses on coverage rather than fitting into a tight space.
Step 1: Determine the Width
Measure the exact width of the window opening. To ensure adequate light control and privacy, you need the blinds to overlap the window on both sides. Add at least three inches to each side of the window opening. For example, if your window opening is 56 inches wide, you should order a 62-inch wide blind. Write down this final, larger number.
Step 2: Determine the Height
Decide exactly where you want to mount the headrail. Most people mount the hardware one to three inches above the window frame or molding. Measure from your desired starting point at the top down to where you want the bottom of the blinds to rest.
If your window has a prominent sill, measure down to the sill. If it has no sill, you might want the blinds to drop two to three inches below the bottom of the window opening to block maximum light. Record this total height.
Measuring Tips and Tricks for Ultimate Accuracy
Even with clear instructions, capturing the perfect numbers requires attention to detail. Follow these expert tips to ensure accuracy.
- Measure to the Nearest 1/8th Inch: Do not round up or down to whole numbers or half inches. If your measurement falls on a 1/16-inch or 1/32-inch mark, round down to the nearest 1/8-inch. This tiny adjustment prevents the blinds from being built too large for the space.
- Format Your Numbers Correctly: Always record your measurements in a strict Width by Height (W x H) format. This is the universal standard for custom blinds. Swapping these two numbers is the most common reason people order incorrect sizes.
- Measure Every Single Window: Even if two windows look identical, they rarely are. Framing differences and house settling mean that windows right next to each other can have slightly different dimensions. Never assume one measurement fits all.
Common Mistakes to Avoid When Measuring
First, never take your own deductions. Many people measure their inside mount window and then subtract half an inch to ensure the blinds fit. Do not do this. Provide the factory with your exact window opening measurements. The manufacturer calculates and takes the precise deductions required for that specific product.
Second, do not measure the old blinds. Materials stretch, warp, and age. Measuring your old, worn-out blinds will almost certainly result in incorrect dimensions for your new window treatments. Always measure the hard window opening itself.
Finally, ignoring window hardware creates installation headaches. Look out for crank handles, alarm sensors, or unique latches on the window frame. These obstructions take up space and might interfere with how your new blinds hang or operate.
Conclusion
Ordering custom window treatments represents a significant investment in your home. By taking the time to measure your windows correctly, you protect that investment and ensure a stunning final product. Whether you choose the sleek profile of inside mount blinds or the broad coverage of outside mount blinds, accuracy is your best friend.
Always use a reliable steel measuring tape, check your windows for squareness, and strictly adhere to the Width by Height format. If you follow the detailed steps outlined in this guide, you can confidently submit your order knowing your custom blinds will arrive perfectly sized for your space. Grab your notepad, start measuring, and get ready to transform your windows.
FAQs About Measuring Windows for Custom Blinds
Do I need to make deductions for inside mount blinds?
No. You should always provide the exact dimensions of your window opening. The manufacturer automatically takes a small deduction (usually about 1/8 to 1/2 inch, depending on the product) so the blinds can operate smoothly without scraping the sides of the frame.
What should I do if my window is not perfectly square?
If your diagonal measurements reveal that your window is significantly out of square, an outside mount is usually the best solution. Outside mount blinds cover the entire window area, completely hiding the asymmetrical framing underneath.
Can I mount blinds outside if I have window molding?
Yes. You can mount the brackets directly onto flat wood molding, or you can mount them on the wall completely above the molding. Just make sure you account for the depth of the molding when choosing your brackets so the blinds clear the trim when lowered.
How do I measure a window with no sill for inside mount blinds?
If your window lacks a bottom sill, measure the height down to the point where you want the blind to end. Usually, this is the very bottom edge of the drywall opening. Provide this exact measurement, and the blind will be crafted to rest gently at that point.
