How To Measure For Replacement Windows and Doors

Measuring windows and doors is not a complicated task. Here is all the information and details you need to know and follow. Read more!
How To Measure For Replacement Windows and Doors

When shopping for replacement windows or doors, having accurate measurements is critical. Buying the wrong size is a waste of time and money, because a proper fit is not negotiable.

Measuring windows and doors is not a complicated task. All you need is a tape measure, a notepad, a pen or pencil. Consider enlisting a helper to hold the tape measure when measuring larger windows or doors. Follow the instructions below.

How to Measure Windows

7 Basic Tips

1. Be sure to take the measure of each window, even if they’re in the same room and appear to be the same size.

2. Work from the window frame, not the glass.

3. Measure width from left to right.

4. Confirm height working from top to bottom.

5. Record measurements to the nearest 1/16 inch.

6. Use a width by length format: a window that is 48 inches wide and 72 inches long is noted as 48″ x 72″ (spoken as 48 by 72)

7. When measuring a multi-pane window, take a picture of it and record the measurements on the printed image. Write down the width and length of each window section and subsections. For example, a 60″ x 20″ window can be composed of two 30″ x 20″ windows.

Measuring Windows

Checking Windows for Square

The first step in measuring for replacement windows is to determine that the corners of the existing window frame are square. Though standard window sizes vary, they have 90-degree corners.

1. From the inside of your home, hold the tape measure in the right top corner where the horizontal and vertical trims meet.

2. Extend the tape measure diagonally to the lower left corner where the trims meet. Record the measurement.

3. Measure from the upper left corner to the lower right corner.

4. If the two measurements are within 1/4 inch of each other, most standard window sizes you purchase will securely fit in your window opening.

5. If they are not within 1/4 inch of each other, you will need to square the frame or find an alternate replacement solution.

Measuring Width

1. From the inside of your home, measure the distance from the inner edge of one side jamb to the other. The side jamb is the vertical piece of trim on each side of the window. If your window is finished with drywall instead of jambs, measure the distance between the drywall on each side.

2. Measure from the surface of the jambs, not from the trim strips or parting beads in your old window opening.

3. Take three horizontal measurements: top, middle and bottom of the window opening.

4. You will choose the smallest of these three measurements to purchase the replacement window.

5. Round up to the nearest inch and record your measurement.

How to Measure Height

1. Remember not to include trim in your measurements.

2. Measure the distance from the high point of the sill of the window (the surface closest to the inside of the window, not the horizontal trim board that extends from the wall) to the top of the window opening.

3. If your window is finished with drywall at the top instead of a head jamb, measure up to the drywall.

4. Make three measurements: left side, center and right side of the window opening.

5. Choose the smallest of these three height measurements for replacement window.

6. Round up to the nearest inch and record.

How to Measure Window Depth

Depth usually isn’t considered when measuring and ordering new windows. However, depth could be an issue if the window opening is too narrow or too deep for a new or replacement window, so you should measure for depth.

1. Ignore all pulleys and parting strips when measuring for depth dimensions. They’ll be removed for replacement window installation.

2. Measure the jamb depth of the existing window. Run a tape measure from the outside of the frame to the inside. Take the measurement from edge to edge of the window frame.

3. You should do the same in several spots around the window frame. Choose the smallest measurement.

4. Window depth should be at least 3 1/4-inches, especially if you live in a modular or mobile home.

Measuring Doors

How to Measure: Doors

Tips for Measuring Doors

Remember that the door is only the part that opens and closes. Anything else is the frame or trim.

1. Measure door width from left to right.

2. Take three measurements: near the top, at the middle and near the bottom, and choose the largest one.

3. Measure door length from top to bottom.

4. Take three measurements: left side, center and right side, and choose the largest one.

5. For multi-sectional doors: measure overall width and length first, then each component door separately.

How to Measure Sliding or Hinged French Patio Doors

1. Step outside your home so you’re facing the exterior of your door.

2. Width:

a. Measure the door at the center. Extend your tape measure horizontally from wall edge to wall edge.

3. Height:

a. Extend the tape measure vertically from the header to the bottom of the door sill, siding to the bottom of the door sill or wall edge to the bottom of the door sill.


If you think your measurements aren’t totally accurate, don’t worry. Our experts will confirm each of them and perform an installation inspection before ordering your new or replacement windows and/or doors. For more information about Air Master products and services, call (787) 999-0717.