Whether you’re replacing existing windows, installing new ones, or adding window treatments such as blinds or curtains, it is important that your measurements are accurate. Proper measurements ensure proper fit and will save you from functionality and aesthetic issues. This guide provides clear instructions on how to measure window size, along with essential tools and expert tips to ensure the job is done right.
Contents
Windows Glossary
Before we begin, let’s explain some common window terms that you will have to know before proceeding:
Sill
The bottom part of the frame that rests on the windowsill can be one piece with the frame or an addition of a separate trim.
Jambs
The side pieces of the frames running vertically have to be measured as accurately as possible, since they form the guides between which the sashes will work.
Head
The top part of the window frame. It is essential to measure this area in order to provide a proper fit and function for both window replacements and treatments.
Tools You Will Be Using to Measure Your Windows
You will not require specialized tools for measuring your windows; you will most likely already have them.
You will need:
- A measuring tape
- A level
- A pencil
- A notebook or sheet of paper
Pro Tip: Keep your tools organized to save time while measuring multiple windows in one session.
How to Measure Window Size for Replacement Windows
Measuring for replacement windows requires accurate measurement of the existing window frame. The goal is to order a new window that fits properly into the space. Here’s how to do it:
Measure the Width
Measure the inside from the left jamb to the right jamb in three locations: top, middle, and bottom. Take the smallest of the three to ensure the window will fit. The width could be different because the frame may have settled or warped over time.
Measure the Height
Take a measurement from the inside of the top jamb down to the inside of the bottom jamb in three spots-left, middle, and right-using again the smallest measurement for the best fit. This is necessary because the height sometimes varies from top to bottom, with much greater frequency in older homes.
Take the Measurement
Measure from inside the window frame at the point where the window meets the jamb, outward to the exterior wall. To that length, add 3 1/4″ for the nominal width of a regular window frame and the room for any clearance. That should ensure your window fits properly. It helps to show whether there is additional framing that could be involved, or some kind of adjustment.
Check the Sill Level
A level tool should be used to ensure the window sill is perfectly level. If the sill is not at level, this will affect the window performance; for any opening window, especially, this can be essential. A level sill ensures a functional and aesthetically pleasing window.
Important Tip: If your window has non-standard shapes or angles, it’s advisable to hire a professional to take measurements or carefully follow the manufacturer’s guidelines for irregularly shaped windows.
How to Measure Window Size for New Construction Windows
For new construction windows, you’ll need to measure the rough opening in the wall rather than an existing frame. Here’s how to do it:
Measure the Rough Opening Width
Go side to side, taking a measurement from jamb to jamb of the opening. Subtract about 1/4 to 1/2 inch to account for the frame of the window. This will provide room for the actual frame of the window to fit into the opening, with wiggle room for adjustments and insulation.
Measure the Rough Opening Height
From the top of the opening to the bottom, take the measurement. Again, subtract about 1/4 to 1/2 inch to allow for a proper fit. The rough opening should be slightly larger than the window itself to allow room for insulation and proper installation.
Check for Square
Use a square to ensure the rough opening is square. Measure the diagonals of the rough opening. If the measurements differ, the opening may be out of square, and adjustments will be necessary to fit the window. It’s vital that the opening is square for optimal window installation.
Measure Depth
Take a measurement from the outside of the wall to the inside. It will give you a clear view of how deep the frame needs to be for perfect fitting. Certain types of windows, especially energy-efficient windows, may require more depth for proper installation.
How to Measure Window Size for Blinds and Curtains
For Blinds
Inside Mount Blinds: Take the width inside the window frame at the top, middle, and bottom. Take the smallest of these measurements for the width. For height, take a measurement from the left side, middle, and right side, then use the smallest.
Outside Mount Blinds: Take width and height measurements around the area the blind would go. Add 2 to 3 inches to each side to allow for maximum light control and privacy.
For Curtains
Width: Measure the width of the window, with its frame, adding 4-8 inches to either side for full coverage.
Height: Take your measurement from the top of your curtain rod or where you will be mounting it, down to where you want your curtain length. Common lengths include just below the sill, to the floor, or pooling slightly on the floor.
Pro Tip: For curtains with decorative rods or finials, consider the extra width these might add.
Expert Tips for Measuring Windows
Take Multiple Measurements: Measure at several points (top, middle, bottom for width; left, center, right for height) and use the smallest measurement.
Measure Twice: Double-check your measurements to avoid mistakes.
Account for Trim: Include window trim and molding if measuring for blinds or curtains.
Check for Square: Measure the diagonals to ensure the frame is square.
Consider Hardware Placement: Account for hardware that may be needed, such as curtain rods or mounting brackets, when measuring for window treatments.
Check for Obstructions: Look out for obstacles that could affect your measurement, such as handles, locks, or trim.
FAQ’s
How do I know what size window I have?
To measure for a window, take the width at the bottom, middle, and top of the jamb, and take the height at the longest and widest visible opening. If there is a frame, take your measurement from the outer edge.
How to calculate window size?
To measure for a window’s size, measure the width and height from the inside edge of the frame. For width, measure across the top, middle, and bottom. For height, measure from the top to the sill on both sides and the center. Include the frame if applicable.
Do window sizes include the frame?
Remember that window sizes generally refer to the opening and do not include the frame unless the question includes it. To measure size, always measure from the inside, using the very outer edges of the frame for sizing.
How to measure to fit a window?
Measure width at top, middle, and bottom and height at left, center, and right-using smallest measurements. Then, measure the depth of the frame, checking diagonals to make sure it’s square. Don’t measure the old frame.
Conclusion
Measuring your windows well now will save you unnecessary time and costs that come with mistakes, while also enabling your new windows or window treatments to just fit perfectly in place. Now and later, the right tools and proper technique will help you enjoy a smooth process in adding functionality and appearance to your space.
If you’re looking to upgrade your windows, get in touch with Mannlee today for the high-quality windows that suit your particular needs. We have a selection of window styles and sizes suitable for any project. Let us provide the perfect windows for your home or business, ensuring years of quality and performance.
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