how to measure windows

Mistake-Free Guide on How to Measure Windows




It’s crucial to understand which measurements to take, whether having storm windows installed or hanging new curtains. Measuring windows to find the right size for replacement isn’t a difficult task, but accurate measurements are vital. Take your time to get it right, since purchasing the incorrect window size will waste much more time and money.

This guide will educate you on how to measure replacement windows, window screens, storm windows, round windows, plus useful tips.

Why You Should Measure Windows with a Professional?

New windows are an investment that will give cost-savings and a whole new look for the home, but only if you choose the right size windows for your house.

Measuring windows yourself is a great starting point to determine your general budget, but it’s highly recommended to consult with a local window repair company to get truly correct measurements. The last thing you want to have is a window that’s too small for the opening and, therefore, less efficient or a window that’s too large and cannot be installed.



It’s also best to work with a window replacement company to install your new windows. Most people replace their windows since they want to save on their utility costs. Windows that fit poorly thanks to a bad installation can produce a range of issues, from high heating bills to uncomfortable drafts. According to the U.S. Department of Energy, up to one-third of a home’s heat loss occurs through its doors and windows.

Professional window installers have experience and tools to ensure your new windows look exceptional and perform exactly as they’re designed to.


How to Measure a Window for Replacement

Read on as we show you the correct steps to learn how to measure windows for replacement accurately.

Required measuring tools

  • Measuring tape;
  • Paper and pencil;
  • Slide rule;
  • Ladder.

Step 1: Take three horizontal measurements of the window frame for the width

  • Measure the distance horizontally across the frame at the top, at the middle, and at the bottom from each side jamb;
  • Circle the smallest measurement of the three numbers;
  • The smallest measurement is the rough opening width, the main measurement to reference when buying a replacement window.
Measure Horizontally


Step 2: Take three vertical measurements of the window frame for the height

  • Measure the distance vertically across the frame from top to bottom on the right, middle, and left side of the window from the window sill to head jamb;
  • Circle the smallest measurement of the 3 numbers, this’s your rough opening height.
Measure Vertically


Step 3: Take the depth of the window’s opening

  • Finding the correct depth is crucial since some windows will be too deep to fit into a replacement window opening;
  • Release a tape measure from the outside of the frame to the inside and record the measurement from edge to edge of the frame;
  • Repeat the action in several locations around the window frame and rely on the smallest measurement once again as your concluding dimension.
Measure Depth


Tip – Before you begin taking the measurements, you have to inspect the frame. If it’s rotten in some places or has some other form of damage, you’ll need to repair or change it. Otherwise, the replacement windows won’t do you much good.

Window screens measuring

Learning how to measure window screens isn’t so complicated. If a screen is replaced and the existing damaged screen is available, or another window of the same size screen, just measure height and the screen width.

Follow the instructions below.

  • Survey the distance between the screen channels on the window frame. Take away 1/8-inch from the measurement for the width dimension;
  • To take the height of the new screen, raise the window sash and gauge from the lip along the screen channel to the sash. Sum 1/8-inch to the measurement for the height dimension.

How to measure storm windows

The process for measuring storm windows is similar to determining measurements for single- or double-hung windows.

To take the width, measure jamb-to-jamb from the inside of the trim on one side to the trim’s inside on the other side of the window.

  • Survey at the bottom, middle, and top of the window;
  • Note the shortest measurement as the width.

To measure the height, survey from the sill to the inside of the trim at the top of the window.

  • Gauge the left, center, and right side of the window. Write the shortest measurement as the height of your storm window;
  • Applying the smallest measurements for the height and width will ensure that the storm window’s flanges will fit appropriately inside the exterior trim of the window’s opening.
how to measure for a new window

Round window measuring

Measuring a window curved or features a round top can be a challenge at first, but it’s still relatively simple. There are various specialty windows applications, but most have some sort of curvature that needs to be measured for replacement.

  • Start by measuring the square part of the window and excluding the arched portion of the window;
  • Next, record a measurement from the window’s lowest point to the arch’s highest point. This will always be in the exact center of the window. Remember to not consider any trim pieces in your measurements.


Why are Accurate Window Measurements Important?

Having accurate window measurements in advance can save you a lot of trouble in the long term. While replacing a window typically isn’t a complicated home improvement project, even minor inaccuracies can turn a simple project into a nightmare. Incorrect measurements may result in a poor fit, leading to future issues. Accuracy is the key to ensuring a proper fit and installation, which may maximize energy savings.

Make an in-home consultation to receive accurate measurements before ordering. Still, many homeowners like to measure from home before visiting a showroom. This will give you a better clue of size requirements and help you shop with calmness, as you’ll be able to get a rough idea of size, style, and preference.

What are the Standard Window Measurements?

Most windows feature standard, consistent dimensions designed to fit into the common rough opening sizes in homes. If your house has standard rough openings, you can opt from a wide diversity of standard windows that can be put right into the openings. While these dimensions won’t work for every window replacement, they’re tailored to fit most homes.

Get a grasp two of the most standard window size measurements:

  • 2020 window – The 2020 opening is a common type of window within most standard homes and measures 24 x 24 inches, width by height. There is a half-inch taken off of the width and height of the window to ensure proper fit, making it a 2020 window. These dimensions are common in both old and new houses;
  • 3038 window – Another standard window size is the 3838 window. This type is given its name because it measures 44 x 44 inches in size, but a half-inch is taken off for height and width.
how to measure replacement window

How to Measure for Replacement Windows – Best Tips

Extra tips for how to measure windows include:

  • Measuring only to the interior trim of the windowsill and the sash stop will result in the new window being too small;
  • Take all measurements from inside the home;
  • Correct size numbers will ensure the windows install adequately, and will aid to maximize energy savings;
  • When planning a window replacement project, it’s pivotal to approach the steps in your project in the right sequence. Measure your windows first, then pick, and buy replacement windows. Only then you should remove old windows to make ready for the new windows;
  • Standard replacement window project should take about an hour to complete; the time may vary based on the project’s specific requirements;
  • Once the window is in place, make sure the window is square — the window frame should sit ideally square with the sides straight;
  • Whether you’re changing a single window or every window in the house, carefully record the measurements as you take them.


Most Common Windows Measuring Mistakes

These are the 5 most common mistakes you must avoid while measuring a window.

  • Not measuring the windows separately – Often, homeowners fail to distinguish between windows of the same style and size. So, you must remember that the dimensions of windows seeming identical may differ thanks to framing. Therefore, you must measure the windows separately;
  • Not measuring width and height in 3 places – In addition to measuring the windows individually, you also have to measure their width and height in 3 distinct places — bottom, top, and middle. When you measure the height/width in 3 areas, it becomes easier to capture the difference in sizes of the bottom and top openings;
  • Neglecting window depth – While measuring a window, homeowners often ignore to survey its depth. You can’t choose the right window blinds without measuring a window’s depth, height, and width. It’s always critical to measure window depth from the edge of the opening to the glass;
  • Measuring window openings just from the inside – There are always chances that you may choose hanging the covering on the outside of the window. You can’t cover a window externally without measuring the width and height of its opening from outside. You can use the steel tape to take 3 evenly stepped measurements and determine the largest point;
  • Forget to double-check window measurements – Many people purchase wrong-sized windows by mixing up a window’s height and width. It’s always important to measure the height, width, and depth precisely. Hence, you must not forget to double-check the measurements.

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