How to Measure Windows for Blinds: 3 Tips for Measuring

Window blinds are shades in homes and other spaces that limit or keep out sunlight, increase privacy, and enhance interior design. Blinds are made from hard materials like wood or vinyl, unlike drapes and curtains. There are also faux wood blinds that are more durable and moisture-resistant than standard wood blinds. Blinds have slats that can be angled open with a mechanism or pulled with a cord for light control, customizing the amount of privacy and sunlight you get in a room. (Blinds also come in cordless versions.) Horizontal blinds work well for small windows, while long, vertical blinds usually pair with sliding glass doors.

Inside mounts are mounted and fitted within your window’s frame or trim. Follow these steps to properly measure the window casing to optimize functionality:

1. 1. Depth: The depth will be the smallest measurement—take measuring tape and record the distance from the window’s glass to the edge of the window frame. This measurement is important, as different blinds will have different depth requirements. Be sure to check the measurements on blinds before purchasing.
2. 2. Width: Measure the width by placing your measuring tape inside your window casing on the left side. Moving your tape in a straight line, measure the left edge to the right one, bending the tape perpendicularly when reaching the right side to get an accurate measurement. Sometimes frames warp, so be sure to measure at three locations (the top, middle, and bottom) of the inside of your window frame. Choose the narrowest measurement so your blinds are correctly sized.
3. 3. Height: Measure the height of your window from within the casing. Your measuring tape should stretch from the bottom side of the casing at the top of the window to the top of the sill at the base of the window.

Outside mount blinds sit outside of a window frame, offering more light control. These are also good for window casings without enough depth and are often accompanied by a valance. Follow these steps to measure for outside mount blinds:

1. 1. Determine the headrail point. Before you take out the measuring tape, first mark the headrail—the top part of your blinds outside of the window. Make a small “x” with a pencil where the center of your headrail should be.
2. 2. Measure the width of the window. Measure your window’s width with steel measuring tape inclusive of the casing (trim or frame). Add an inch or two to each side (so, up to four inches total) to calculate how wide your blinds should be.
3. 3. Measure the height of the window. Measure the distance from your window sill up to the pencil mark you made for the headrail. If your window doesn’t have a sill (sliding doors, for example), you can measure from your pencilled “x” mark down to the desired stop point. This may be the floor or another point, and you can factor in an extra inch for flexibility. With these recorded measurements, you will have everything you need to purchase the correctly-sized blinds.

If you are getting customized blinds or purchasing blinds from a store, ensure you have the correct measurements for an efficient installation process. Consider these measuring tips, whether you’re installing roller shades, solar shades, or vertical blinds:

1. 1. Measure to the nearest eighth inch. Most blinds will be measured to this degree of precision, so be sure your tape measures in eighth inches.
2. 2. Measure all of your windows. Whether you are moving into a home with existing windows or are installing new windows yourself, be sure to measure each window separately. Before making a purchase, record the measurements of each window, as window sizes may slightly vary.
3. 3. Remove all obstructions. To get the best measurements, remove any plants, books, or knick knacks that sit on your window sills; simply measuring around them won’t give the most accurate height or width measurements.

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