Doors may not always come in the exact same sizes. Depending on the style of your home’s entryway, the door may be wider than usual. So with door replacement projects amounting to $1,500 or more, taking a wild guess at the size will not be sufficient if you do not want to waste your investment in this home improvement project.

Do not worry, though, because even if you are not a professional or door expert, you can still take accurate measurements to prepare for your door replacement.

You need to use specific tools that are not too hard to find and learn the necessary steps for doing the task. As you continue reading, you will discover how to measure for a door replacement to determine what door size your home’s entrance requires.


Tools You Will Need for Door Measurements

Regardless of the type of door you are measuring – hinged or sliding – you will need the same group of tools for the task.

  • Tape measure: Measuring the door and door frame using your bare hands or arm’s length is inaccurate, so it is always best to use a tape measure.
  • Pen and paper: You need these to write down the measurements instead of remembering them. You can also use your phone’s note app.
  • Stepping chair or ladder: Unless you can easily measure the highest part of the door, you will have to use something safe and sturdy to step on.

How to Measure For a Hinged Door Replacement

Entryway installations for homes usually involve hinged doors, whether for the entrance to the house or to get inside rooms. The entry doors are generally the heavy type and come with insulation. However, the main characteristic of this door is that the installer attaches it to the frame through hinges.

The rule of thumb for a hinged door is to measure it from the side where the hinges are. To be more accurate, you should take the measurement from inside the house or room. Also, you need to get the dimension from the actual panel that opens and closes. Remember not to include the frame in your measurement.

You can also round up or down if you have a hard time determining the accurate measurement down to the exact decimal value. Round up if you will be purchasing a wood door as you can easily perform sanding if it is larger than it should be. On the other hand, you should round down if you plan to get a fiberglass or steel door.

Step 1: Measure the Width of the Door

Using your tape measure, get the door’s width from these three areas – bottom, middle, and top. Close the door and stand behind it. Lock the door, if necessary, to prevent someone else from accidentally opening it while you are behind the door. Keeping the door locked is even more crucial if you are taking measurements for exterior door replacement.

Start taking the door width measurement from bottom left to bottom right. Remember to record it using your pen and paper or your phone. Then, do the same from the middle left to the middle right. Finally, use your step ladder or chair to measure the width from the top left to the top right. If you end up with slight variations in your width measurements, always go for the largest number.

Step 2: Measure the Height of the Door

Get the height measurement from the top left corner of the door and down to the bottom left. Depending on your reach, you might need to use a stepping ladder or chair to do this more easily. It would be best to have a family member or friend help you out by keeping the chair or ladder stable.

Do the same on the other end, from the top right corner to the bottom right corner. Remember not to include the frame and just measure the actual door panel. If your measurements on both ends do not match, always choose the longest dimension. Keep in mind, though, that you also need to adjust your measurement to accommodate any floor covering you have if this is for an interior door replacement.

Step 3: Measure the Thickness of the Door

You will need to open the door to measure its thickness this time. There are two ways of doing this. One is to run your tape measure across the edge of the door. You can also choose to take the measurement between the stops and the backside of the door jamb. The dimension you will get will be basically the same. So, in general, it is a matter of preference, and you should go with whichever method you are more comfortable using.

Step 4: Measure the Frame Dimensions

Taking the door panel’s dimension should typically be enough when selecting a door replacement. However, if you want to be sure that the new door would fit the existing frame, it is always a good idea to measure the frame’s dimensions as well.

If you choose to do this, you will have to take three different kinds of measurements:

  • Frame width: You can get this by placing your tape measure across the inner side of the door frame. Remember to do this in different vertical positions because if the numbers vary, you should choose the smallest number.
  • Frame thickness: Use your tape measure from the inner area of the side frame to the outer area.
  • Frame height: Depending on the type of door, interior or exterior, you will need to start your measurement from the floor or the threshold, respectively. Extend your tape measure up to the lower part of the door’s upper trim.

How to Measure for a Sliding Door Replacement

The position where you take your measurement for sliding doors is the opposite of what you will have to do with hinged doors. You need to do this from the outside instead. If you are unsure which one is the exterior, that would be the side without the lock.

Contrary to a hinged door, you need to measure the entire sliding door opening since it does not require a gap for trim and weather stripping.

Step 1: Measure the Width of the Space

Using the same set of tools, you can take the width by running your tape measure horizontally across the door. Remember to start and end at the inside of the side jamb. Do this in different areas and pick the smallest number for the most accurate measurement.

Step 2: Measure the Height of the Space

For the height measurement, start from the top of the bottom track and run the tape measure vertically across to the top. You should also do this in different sections and pick the smallest number.

Door Replacement Measuring Tips

Here are some more pro tips you need to know when measuring for a door replacement:

  • Remember to take a hinged door’s measurements from behind since the backside is typically a little wider than the front.
  • The direction of the door swing is often overlooked when replacing a door. So make sure to take note of this too while taking your measurements for your existing door. An inward swinging door opens when pushed towards the room. On the other hand, if you need to pull the door towards your body to open it, it would be an outward swinging door.
  • For wooden exterior or interior door replacement, add a bit of clearance with your measurement. That way, it can accommodate any change in dimension because of the weather. A wood door will eventually contract if exposed to cold weather or expand during the hot months. An allowance of about two to four millimeters should be enough.
  • If you have decorative sidelights, remember to consider their measurement as well. Using the same tape measure, you can get the height by extending the tape vertically and the width horizontally.
  • For a pre-hung door replacement, you will need to remove the trim first with a prybar, so you do not have to include it in your measurement. To figure out the width, start measuring from the outer jamb on one side to the jamb on the other side. You can get the height by extending your tape measure vertically from the sill to the upper jamb. Finally, the measurement for the thickness requires running your tape horizontally across from the side jamb’s inner edge to the exterior edge.
  • If you plan to replace a door for an older home, there are instances when the door might not fit the frame anymore. In this case, you will need to take measurements from the jamb itself. This will help you get a more accurate number for the thickness, width, and height.

Measure with Confidence


Follow these steps to ensure that your new door will fit perfectly with your existing door frame. As you have discovered, they do not require technical skills at all but specific yet straightforward steps on how to measure for a door replacement.

The most important thing to remember before taking the measurement is understanding what type of door you have. Then you will just have to follow the instructions outlined here for the rest. As a general rule, always remember to take several measurements from different areas to account for irregularities in thickness and shape.

Do you need further help in replacing your door? Contact C2 Operations today and schedule a free estimate.