measure windows

How to Measure For Replacement Windows

Are you thinking about getting replacement windows for your home but aren’t sure how to properly measure for sizing purposes? Here’s what you need to know.

Maybe you’re starting to notice a draft in your older home, or your windows are too resistant to opening and closing. Condensation might be building up between the layers of glass, or the frames are wearing away. If you’re noticing these signs, it’s time to replace your windows.

You might get excited and jump into looking for the best replacement windows right away, but you can’t do anything yet. The first step you must take is measuring your home windows.

New window installation starts with knowing the exact sizes of all the windows in your home. Measuring might seem like an easy task, but there are some nuances you must respect if you want the perfect fit.

With a project as expensive as replacing windows, you want to be absolutely sure of your purchase. In this guide, you’ll learn how to perfectly measure your home windows for replacement.

Tools for Measuring Home Windows

When you set out to measure your residential windows, you’ll need knowledge of some important window terms. You’ll also need to know some essential rules of measuring and a few simple tools.

When it comes to talking about windows, you’ll need to know these window terms:

  • Jamb – Click here to see example (opens in a new window)
  • Sash –  Click here to see example (opens in a new window)
  • Sill
  • Header
  • Rough opening

A jamb is a box or frame in which a window is enclosed. The sash is the actual window pane. Jambs are made up of a sill and a header, or the bottom and top respectively.

The rough opening is the actual opening into which you will need to fit your windows. It is called a rough opening because sizes are not exact, but rounded up.

When it comes to measuring, there are some rules you need to follow:

  • Always record all of your measurements width first, height second
  • Always round your measurements down to the nearest 1/8th of an inch
  • Don’t assume your frames are square
  • Measure the interior of the jamb, not out to any trim

To get started, you’ll need these tools:

Now that you know the basics, you can get started. Take your time and double-check your measurements.

Compare Replacement Window Cost

Measuring for Replacement Windows

When you are ready to start measuring for your replacement windows, you’ll need to use your tape measure to measure the width and height of each window. Remember that you should be getting a measurement for the rough opening, so you should keep your tape measure in the interior part of the window jamb.

Make Sure Your Frames Are Square

Making sure your frames are square means making sure that they have a 90-degree angle at each corner. You can make sure your frames are square by following a simple trick.

Imagine an X inside your window frame. You’ll want to measure from corner to corner in an X shape.

  • Measure the space between the top left corner and bottom right corner
  • Measure the space between the top right corner and bottom left corner

These two measurements should be equal within reason. You can allow for a margin of error between 1/8th to 3/16th of an inch. If the measurements are not equal, it means your frame is out of square.

Compare Prices

In the case that your frames are not square, you will want to seek further help from a professional. Attempting to replace windows on your own will lead to unsuccessful installations and costly mistakes.

In extreme cases, you may need to have a professional fix the frames. If your frames are very old and damaged, they’ll need to be replaced as well. In less severe cases, a professional can help fix the angles of the frame before installing windows.

Find the Width of the Window

Because window measurements are always recorded as width first, you should start by measuring the width of the window. Measure your window from side to side of the interior of the jambs.

Take three width measurements:

  • At the top of the window
  • At the center of the window
  • At the bottom of the window

To get the most accurate reading, you’ll need to move the window out of the way. You want to get the measurements from the center-most points of the frame. For example, you should slide the window pane up on a double-pane window to get the bottom measurement, then slide it back down to get the top measurement.

In order to get the correct size windows, you’ll need them to fit into the jamb at the smallest measurement. To ensure the fit, circle the smallest measurement you got from the three width measurements.

Find the Window Height

Now that you have the width, you should move on to the height measurements. You should also keep these measurements to the inside of the jambs and take three separate measurements.

  • At the right jamb of the window
  • At the center of the window
  • At the left jamb of the window

In the same way that you ensured your replacement windows would fit for the width, ensure it with the height. Circle the smallest height measurement you obtained.

Find the Window Depth

In general, standard windows tend to have the same depth. Specialty windows, like those for modular or mobile homes, tend to be thinner. It is always good to check, but it won’t be as important as height or width.

The importance of depth will mostly matter if you are choosing to replace the entire window with its frames instead of just using window inserts.

If you are just using inserts, measure the space from the front to the back of the jamb. Make sure you are only measuring the jamb itself, not any extra trim or siding. The jamb should be at least 3 and 1/4 inches to accommodate the replacement windows.

Most replacement windows are made to fit a jamb measured 4 and 9/16 inches. You’ll only need to check this measurement in one place rather than three places.

Ensure Proper Measurements

Once you have all your measurements, make sure you’ve taken the smallest measurement from each dimension. You’ll also need to make sure you’ve rounded them down to the nearest 1/8th inch.

You can bring these measurements to your chosen supplier or a professional to go over which replacement windows you can choose from.

Custom or Standard Size Windows?

When it comes to windows, there are actually no real standard sizes across the industry. You can, however, find standard sizes within a manufacturer. If there is a specific size window you are looking for, you can find a manufacturer with that size to start.

You can’t always find a manufacturer that provides windows in the size you need. This is less likely for very common types of windows, but if you have special windows in your home, or you own an old home, you might have a hard time finding the right size.

In the case that you can’t find the right size, you might have to custom order windows. This can mean extra costs and a long time waiting for your windows to be delivered.

Types of Replacement Windows

There are many different types of windows you can choose to replace your windows with. You can determine what type of window you want based on its function and style.

If you need good ventilation, a double-hung window is a way to go. This is the most common type of window on the market. The sashes even tilt outward, making it easy to clean the exteriors of your windows without going outside.

If you have a great view outside, you might want to consider sliding windows. These windows come with two or three sliding panels and allow for a wide, less-obstructed view.

Awning windows are crank windows that open upwards to create a type of awning over your window. This prevents water from getting inside when it rains and is a preferable choice for preventing intruders.

If you don’t need a window that opens, you can choose to install a picture window. This allows for an unobstructed view and much less maintenance than other types of windows.

No matter the types of replacement windows you choose, you will be able to measure your current windows in the same way. Just make sure you are buying a window that has the same dimensions as your current windows. Otherwise, you’ll need to change out the rough opening size and frame before you install.

How Much Does It Cost to Replace Windows?

The cost of your replacement windows will range according to brand, quality, style, and location of your window. In general, the standard cost of average windows could land between $250-750 per window.

This price can go up drastically if you are ordering higher quality windows and having them installed in difficult to reach places. It will also be much higher when you are ordering custom-sized windows, and if you’re rushing the delivery schedule.

Higher pricing for windows could land between $850-1250 per window.

Start Your New Window Installation Today

Now that you’re equipped to measure your windows properly, you can get started with exploring your options for replacement windows. The best replacement window company can walk you through the steps and help you find the perfect replacement windows. You’ll no longer have to suffer from your current home windows!

Begin your new window journey today by comparing window contractor costs with

Compare Replacement Window Cost

1 Comment
  1. Sliding doors are doors that open by sliding instead of swinging on hinges. They can be made of wood, glass, or metal and are often used to separate two rooms or as an entrance to a patio or deck.

Leave a Reply