7 Easy Steps to Measure Windows Like a Pro

Measuring windows accurately is crucial for ensuring proper fit and functionality of window treatments or replacements. Whether you’re a homeowner embarking on a DIY project or a professional contractor, precise measurements are essential for achieving seamless results. But fret not, measuring windows is a task that can be easily mastered with the right approach and a few simple tools.

To begin, gather the necessary tools: a measuring tape, a pencil, and a notepad. Start by measuring the width of the window. Hold the tape measure at the inside edge of the left jamb, extend it across the window frame to the inside edge of the right jamb, and note the measurement to the nearest 1/8 inch. Repeat the process for the height of the window, measuring from the top inside edge of the head jamb to the bottom inside edge of the sill. Remember, these measurements represent the rough opening dimensions, which include the frame but exclude the trim or molding.

Next, determine the type of window you have. Common types include single-hung, double-hung, casement, and awning windows. The type of window will influence the measurements you need to take. For instance, for a single-hung window, you only need to measure the width and height of the sash, while for a casement window, you’ll need to measure the width and height of the entire frame.

Measuring for Replacement Windows

1. Determine the Type of Window

Identify the style of the replacement window you need, such as casement, double-hung, or bay window. Different window types require specific measurements.

2. Measure the Rough Opening

Measure the width and height of the rough opening, which is the space in the wall frame where the window will be installed. Measure from the interior side of the frame, from stud to stud and from header to sill.

3. Measure the Existing Window’s Size

If replacing an existing window, measure the height and width of the window’s frame, excluding any trim or exterior siding. Also, note the thickness of the existing frame.

4. Calculate the Window Size for Replacement

Subtract the thickness of the existing window frame from the rough opening measurements to determine the size of the replacement window you need. For example, if the rough opening is 36" wide and the existing frame is 1" thick, the replacement window should be 34" wide.

Measurement	Dimension
Rough Opening Width	36″
Existing Frame Thickness	1″
Replacement Window Width	34″

5. Consider Additional Factors

In addition to the above measurements, also consider the following:

Headroom: Measure the space between the top of the window and the next obstruction, such as a header or ceiling.
Sill height: Note the height of the window sill from the floor.
Flange depth: Determine the depth of the window flange, which is the portion that extends into the rough opening.
Additional features: If desired, add measurements for any additional features, such as grids or muntins.

Method 1: Using a Measuring Tape

This method is simple and straightforward, but it requires a measuring tape and a helper. Start by measuring the width of the window from one side to the other. Then, measure the height of the window from top to bottom. Multiply the width by the height to get the area of the window in square feet.

Method 2: Using a Window Calculator

If you don’t have a measuring tape or a helper, you can use a window calculator to estimate the area of your windows. These calculators are available online and they require you to enter the dimensions of your windows (width and height) in inches. The calculator will then automatically calculate the area of the window in square feet.

Method 3: Estimating Window Area for Energy Efficiency

When estimating window area for energy efficiency, it is important to consider the following factors:

The size of the window
The type of window
The orientation of the window
The climate zone
The efficiency of the window

By considering these factors, you can get a more accurate estimate of the window area that is needed to achieve the desired level of energy efficiency.

Calculating Window Area for Energy Efficiency

The following table can be used to calculate the window area that is needed to achieve the desired level of energy efficiency.

Climate Zone	Window Type	Orientation	Efficiency	Window Area (sq ft)
1	Single-pane	North	Low	12
1	Single-pane	North	High	8
1	Double-pane	North	Low	10
1	Double-pane	North	High	6

Employing a Laser Measure for Precision

Laser measures offer unparalleled precision, making them the ideal choice for measuring windows. Follow these steps to ensure accurate results:

Choose a laser measure with a range that exceeds the window dimensions.
Power on the laser measure and select the “distance” mode.
Stand on one side of the window frame, facing the opposite side.
Aim the laser beam at the opposite frame edge.
Hold the laser measure steady for a few seconds to allow the measurement to be captured.
Record the displayed measurement as the window width.
Repeat steps 3-6 for the window height by aiming the laser beam at the top and bottom frame edges.

Calculating the Window Size

Once the window width and height are measured, calculate the total window size using the formula:

Width (W)	Height (H)	Window Size (W x H)
36 inches	54 inches	36 inches x 54 inches = 1944 square inches

Measure the Width

Place the tape measure at the middle of the top of the window frame. Extend the tape measure to the middle of the bottom of the frame. This will give you the width of the window.

Measure the Height

Place the tape measure at the middle of the left side of the window frame. Extend the tape measure to the middle of the right side of the frame. This will give you the height of the window.

Measure the Depth

Place the tape measure at the top of the window frame, inside the window. Extend the tape measure to the bottom of the window frame, inside the window. This will give you the depth of the window.

Tips for Measuring Windows with Unusual Shapes

If you have windows that are not a standard shape, you will need to use a different method to measure them. Here are some tips for measuring windows with unusual shapes:

1. If the window is curved or has multiple curves, divide it into smaller sections and measure each section separately.

2. If the window is triangular, measure the length of each side and the height of the window from the point to the bottom.

3. If the window is oval, measure the width and height of the oval.

4. If the window has a bay or bow, measure the width and height of each section of the bay or bow.

5. If the window has a transom or sidelights, measure the width and height of each transom or sidelight.

6. If the window has a grill or grid, measure the width and height of each section of the grill or grid.

7. If the window is set in a wall, measure the width and height of the opening in the wall.

8. If the window is covered with a window treatment, remove the window treatment and measure the window following the steps above.

9. If you are having difficulty measuring the window, you can consult with a window professional or use a laser measuring tool.

10. Once you have measured the window, add 2 or 3 inches to the width and height of the opening to allow for the frame and installation.

How to Measure Windows

Measuring windows is crucial for ensuring accurate window treatments, such as curtains, blinds, and shades. Here’s a step-by-step guide on how to measure windows like a pro:

Step 1: Measure the Width

Stretch a tape measure across the widest point of the window frame (known as the exterior casing). Take the measurement from the outer edge of the left casing to the outer edge of the right casing. Record this measurement as “width.”

Step 2: Measure the Height

Measure the distance from the top of the window frame (interior casing) to the bottom of the window frame (interior sill). This measurement should be taken from the point where the top casing meets the side casing to the point where the bottom casing meets the side casing. Record this measurement as “height.”

Step 3: Measure the Depth

If you’re planning to install curtains or shades inside the window frame, measure the depth of the window recess. Stretch the tape measure from the inside of the window frame (where the curtains or shades will hang) to the wall behind the window. Record this measurement as “depth.”