How To Measure Windows For Curtains? Here’s An Ultimate Guide

Have you ever hung curtains that just didn’t fit right? I have, and it taught me that measuring your windows correctly makes all the difference. When your curtains fit perfectly, they look great and work well too—keeping your room cozy and stylish.

In this guide, you’ll learn simple, step-by-step tips to measure your windows the right way. I’ll share my own mistakes and easy fixes so you can avoid the same pitfalls. Ready to discover how a few careful measurements can change your space for the better? Let’s get started!

Essential Tools and Materials

Before you begin measuring, it helps to gather all the tools you’ll need. It’s like making sure you have all your ingredients ready before you start cooking.

Tape Measure: Your best friend for accurate measurements.
Pencil and Paper: For jotting down measurements and notes.
Ladder or Step Stool: Useful if you need a little boost to reach higher spots.
Optional Extras: A level to ensure straight lines and a notepad for extra details.

How To Measure Windows For Curtains? Here’s An Ultimate Guide

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Taking a few minutes to set up your space and collect these tools can save you time and frustration later. Trust me, having everything at hand makes the whole process smoother and a lot less stressful!

Step 1: Deciding on Your Curtain Style and Mounting Method

When it comes to hanging curtains, the first choice is how and where you want them to go. There are two main options:

Inside Mount: This means hanging your curtain rod inside the window frame. It creates a neat, streamlined look and is perfect when you want to show off your window’s trim. However, it requires precise measurements so the curtains don’t look too tight or short.
Outside Mount: This option involves installing the curtain rod outside the window frame—usually above or around it. This style gives the illusion of a larger window and can hide unsightly hardware or trim. It also means you’ll need extra fabric, both for length and width, to ensure full coverage and a fuller look.

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Your chosen style affects your measurement needs. For example, with an inside mount, you need to be very exact with the width and height of your window. With an outside mount, you might want to add extra inches on all sides to create a dramatic, gathered effect.

Have you ever wondered why your curtains looked a bit off? Sometimes it’s all about how you mount them. The right choice can really make a difference in how your space feels!

Step 2: How to Measure Window Width

Measuring for an Inside Mount

When you plan to hang your curtain rod inside the window frame, start by measuring the exact width of the window opening. Here’s how:

Place your tape measure at the very left inside edge of the frame and measure straight across to the right edge.
For accuracy, take measurements at the top, middle, and bottom of the frame, then use the smallest number. This helps if your window isn’t perfectly square.
Remember to account for any trim or molding that might affect where the rod sits.

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“Always measure the full width of the window frame—not just the glass—and add an extra 4 to 6 inches on each side. This extra width lets your curtains pool gracefully and keeps the look intentional.”

– Emily Henderson, Stylist, TV host, and author at Style by Emily Henderson

Measuring for an Outside Mount

If you’re hanging your rod outside the window frame, you’ll want your curtains to cover more than just the window opening. To do this:

Start by measuring the window width as if you were doing an inside mount.
Then, add extra width—usually about 3 to 6 inches on each side. This extra fabric ensures that the curtains can be drawn fully open without blocking any of your window and provides a fuller look.

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“To create a seamless look, I measure from the very edge of the window frame. This ensures that no gaps are left uncovered, giving your room that bohemian, cohesive finish my aesthetic is all about.”

– Justina Blakeney, Designer and Founder of The Jungalow (thejungalow.com)

Practical Examples and Common Mistakes

Imagine your window measures 36 inches wide:

For an inside mount, you’d use the 36 inches as your measurement.
For an outside mount, adding 3 inches on each side gives you a total width of 42 inches (36 + 3 + 3).
A common mistake is measuring from the middle of the window or only measuring once, which can lead to inaccuracies. Always double-check your measurements and measure in multiple places to be sure. Have you ever wondered why your curtains looked too tight or too loose? Often, it’s all in the measuring!

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“A proper measurement is key to a signature farmhouse look—I measure from the window trim to the point where I want the curtains to fall, then add a few extra inches for that soft, draped effect.”

– Joanna Gaines, Co-host of HGTV’s Fixer Upper and design expert at Magnolia

By taking your time with these simple steps, you’ll avoid those frustrating moments of mis-measured windows and enjoy a perfect fit every time.

Image by decorsteals

Step 3: How to Measure Window Height

Start by deciding exactly where you want your curtains to begin and end. Here’s how:

Determine the Start Point:
Decide where the top of your curtain will be. For an inside mount, it might be right at the top of the window frame. For an outside mount, you might place the rod a few inches above the frame.
Decide the End Point:
For floor-length curtains, measure from the rod to the floor. For sill-length curtains, measure down to the window sill or your desired length.

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Adjust for Style:
If you’d like a puddle effect or extra fabric at the bottom, add a couple of extra inches—usually 2 to 4 inches. This gives your curtains a soft, luxurious look.
Double-Check Your Work:
Always measure a few times, especially if your window isn’t perfectly level. This ensures accuracy and helps you avoid common mistakes.

“For a relaxed, California-inspired vibe, I always advise measuring both the window’s width and height carefully, and then extending the curtain rod a few inches beyond the frame to let in as much light as possible when the curtains are open.”

– Amber Lewis, Founder of Amber Interiors

By following these simple steps, you’ll get the perfect height for your curtains every time.

Step 4: Additional Measurement Considerations

Dealing with Obstacles:
Sometimes, windows aren’t perfectly simple—there might be handles, extra molding, or uneven frames. In these cases, measure around the obstacles. For example, if a window handle sticks out, note its position so your curtains won’t get caught. Have you ever found one measurement just didn’t work because of a small, unexpected detail? Measuring a few times in different spots can help you spot these issues early.

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“Accurate measurements are the foundation of beautiful drapery. I always remind my clients to include the entire window—including the frame—in their measurements so that their curtains are both functional and visually balanced.”

– Sarah Sherman Samuel, Designer with a minimalist, modern aesthetic

Accounting for the Curtain Rod and Hardware:
Don’t forget that the rod and brackets add extra space. If your rod is mounted outside the window frame, include a few extra inches in your measurements for both width and height. This ensures your curtains have enough fabric to drape nicely without looking too short or too tight.
Tips for Irregular Windows or Multiple Setups:
For windows with unusual shapes or if you’re working with several windows at once, take your time. Measure each window individually, paying close attention to any curves or angles. Writing down each measurement can help you decide if a custom approach is needed for each section. This extra care can prevent later surprises when it’s time to hang your curtains.