How to Measure Old Wood Windows for Replacement

Replacing old wooden windows can be a daunting task for even the most experienced do-it-yourselfer. Replacing an old wooden window may seem like a daunting task, but it doesn’t have to be. Before you embark on this project, it’s essential that you measure your existing windows correctly so that you can purchase the new window replacements with confidence.

With the right information tailored to your specific situation and products, measuring and replacing wood windows is surprisingly straightforward – all it takes is patience and attention to detail. To save yourself time and money in the long run, ensure that your new window fits perfectly by learning how to measure old wood windows for replacement correctly. Read on to learn some of the most important steps for measuring up your existing frames accurately!

How to Measure Old Wood Windows for Replacement

Things to Keep in Mind While Measuring Old Wood Windows for Replacement

1. Size and Shape

The first step in measuring an old wood window for replacement is to measure the size of the existing frame. Measure both horizontally (across) and vertically (down). Note any odd angles or shapes, as these will impact the measurements you take and how your new window fits into the frame.

2. Window Type

Next, identify the type of window you have in your frame. Is it double-hung, casement, or sliding? Each style requires different measurements and will require different installation instructions for the new window.

3. Existing Hardware

In addition to size and shape, you’ll also want to note what kind of hardware your existing window has attached to it. This includes any hinges, locks, handles, and other items that are attached to the frame. These pieces of hardware will also need to be taken into account when replacing your window.

Required Items

Before beginning the window replacement project, it is important to make sure you have all of the necessary materials. You will need

  • A measuring tape
  • A pencil or pen
  • Paper
  • Plastic sheets or drop cloths

10 Ways How to Measure Old Wood Windows for Replacement

1. Width and Height

Start with the outer dimensions of the frame. Make sure to measure from edge-to-edge for both the width and height of your window frame, recording all numbers in inches on a piece of paper. The height should be measured from the top of the window frame to the bottom. The width should be measured from one side of the window frame to the other.

Start With the Outer Dimensions of the Frame

2. Depth

Next, measure the depth of your existing window frame. This number tells you how deep your window unit is and allows you to choose a replacement with similar dimensions. Measure from front to back on the window frame, recording your number in inches.

3. Check for Obstructions

Look around the outside of the existing window frame to make sure that there are no obstructions that will affect your new window’s fit. This might include moldings or other trim, as well as walls or corner pieces that extend out into the frame area from the wall.

4. Height from Floor

Now, measure the distance from the floor to the top of your window frame. This measurement will let you know where to install your new window unit in relation to the floor surface and will help ensure that it fits in with the rest of your room’s décor.

5. Width Between Jambs

Measure the distance from one side of the window jamb to the other. This number tells you how much space is between your window jambs and lets you know if your new window will fit in the existing opening.

Measure the Distance 
From One Side

6. Existing Hardware

Measure any hardware that is already attached to your existing window frame, such as handles, locks, or hinges. This will allow you to purchase the appropriate replacement hardware, ensuring that your new window operates correctly and fits properly in the frame.

7. Notch Measurements

If your existing window has any notches or cutouts for handles, locks, etc., measure these as well. Be sure to measure both the length and width of each notch so that you can purchase a replacement window with the same size notches.

8. Measure Openings and Clearances

Measure any openings or clearances that will need to be taken into account when purchasing your new windows, such as the distance between the edge of the window frame and nearby walls or moldings. This ensures that your new window fits perfectly in its designated spot.

9. Measure Sill

Lastly, measure the width of your existing window sill. This measurement will let you know how wide your new window needs to be so that it fits correctly on top of the sill. Measuring the depth of the sill is also helpful, as it will tell you how deep your window unit needs to be.

10. Double-Check Measurements

Before you purchase any new windows, make sure to double-check all of your measurements and calculations. Make sure that they are accurate and that your window unit will fit correctly in the designated opening before purchasing.

By taking these simple steps to measure your existing windows, you can ensure that the new window replacement will fit properly and look great when installed. With a little knowledge and patience, you’ll be able to successfully replace old wooden windows with ease.

Make Sure to Double-Check 
All of Your Measurements

8 Common Mistakes to Avoid

When measuring old wood windows for replacement, it is important to be precise in order to make sure you get a window that fits perfectly. However, many homeowners make common mistakes that can lead to significant problems down the road. Here are 8 common mistakes to avoid when measuring old wood windows:

1. Not accounting for obstruction is a common mistake people make. Make sure to take into account any molding, trim, or siding that may obstruct the window when measuring. Otherwise, the window won’t fit correctly.

2. Overlooking existing frames can lead to problems as well. If the existing frame is in good shape, it can be reused, and you should measure it instead of measuring only the glass portion of the window.

3. Not accounting for sash weight is another mistake many people make when taking measurements for old wood windows. Sash weight is the weight of the window when it’s open, which affects the amount of space needed for installation.

4. Not measuring in multiple places can also cause problems because it could lead to an inaccurate measurement overall. Make sure to measure at least three different points on each side of the window and take an average of them.

5. Not measuring the window from the outside is another common mistake to avoid when measuring old wood windows for replacement. The external measurement should be taken from the outside of any trim or siding that may be present, not just from the edge of the glass.

6. Not taking into account non-standard measurements can lead to problems as well because most windows are built to standard measurements. If the window opening is an odd size, make sure it’s measured accurately so that you order the correct size replacement window.

7. Not taking into account the manufacturer’s instructions can also be a mistake. Different manufacturers have different installation requirements, so make sure to read their guidelines before ordering any windows.

8. Finally, not double-checking all the measurements can be a costly mistake. Make sure to double-check all of the measurements before ordering any windows, as it’s much easier (and cheaper) to fix a measurement error before you place an order than after.

Manufacturers Have Different 
Installation Requirements

By avoiding these 8 common mistakes when measuring old wood windows for replacement, you can ensure that you get the perfect window for your home.

Frequently Asked Questions

How Long Will It Take to Finish the Project?

The length of the project will depend on the size and complexity of the window, as well as any additional materials that are needed for installation. Generally speaking, a straightforward replacement window can take anywhere from one to three days to complete.

Do I Need to Hire a Professional?

Replacing an old wood window can be done by a homeowner if they have the right tools and knowledge. However, hiring a professional is recommended if you want to make sure the window fits correctly and is installed properly without any issues.


It’s important to gather accurate measurements prior to purchasing a replacement window. It’s also worth noting that some windows may require custom-made replacements due to their age and design. Be sure to measure your windows correctly and with precision in order to ensure that the replacement will be an exact fit. Now’s the time to take action if your old wood windows are in need of repair or replacement.

With the proper knowledge and steps of how to measure old wood windows for replacement, you can easily measure old wood windows for a new installation without compromising on function or aesthetics. Investing in high-quality replacement windows can make all the difference between an outdated space and one that’s fresh, modern, and inviting. Take advantage of this opportunity now by assessing the situation and starting your project on the right foot – remembering that accuracy is key when measuring old wood windows for a new installation.

Leave a Comment