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How to Measure Internal Doors

How to Measure Internal Doors - A Step by Step Guide

Internal door sizes can vary depending on the style of door, and if you don't measure correctly, you may end up with a door that's either too big or too small for the opening. If the door is too small, it will be difficult to open and close. On the other hand, if the door is too large, it will leave an unsightly gap around the frame. 

If you're looking to add new doors or replace the existing doors in your home, it's important to get accurate measurements. In addition, doors come in a variety of thicknesses, so it's important to measure the thickness of your existing doors before selecting new ones. By taking careful measurements, you can ensure that your new doors will be a perfect fit. 

How to Measure Internal Doors

To ensure a proper fit, take a few simple measurements before placing your order. To start, measure the width of the rough opening. Next, measure the height of the rough opening from the top of the opening to the bottom of the header. Finally, measure the depth of any existing trim around the door frame. 

  • Measure the Door Width

Measure the Door Width

When measuring for an internal door, start by measuring the width of the door. This is the distance between the studs on either side of the opening. To get an accurate measurement, use a tape measure and measure from one side of the door frame to the other. If the doorframe is not levelled, you will need to take multiple measurements and use the average.

  • Measure the Door Height

Measure the Door Height

The easiest way to measure an interior door’s height  is to measure from the top of the doorframe to the floor or the bottom of the header using a tape measure. Again, if the door is not levelled, you will need to take multiple measurements and use the average. 

  • Measure the Door Thickness

Measure the Door Thickness

The door thickness is especially important, as this will determine the size of the hinges that you need. To measure the door thickness, use a tape measure to determine the distance between the door stop moulding and the edge of the door. Then, add an additional 1/8 inch to account for any irregularities. 

How to Measure French Doors

Measuring French doors is a relatively simple task that can be completed in a few minutes with a tape measure. Keep in mind that French doors typically have a larger rough opening than their finished size, so be sure to account for this when measuring French doors.

  • Measure the Door Width

The width of a French door is measured in two ways. The first is the overall width, which is the distance between the two door panels at the widest point. The second is the net width, which is the distance between the door panels after the handles and other hardware have been taken into account. 

To find the overall width, simply measure from one side of the door to the other at the widest point. To find the net width, first measure from one side of the door to the other at the widest point. Then, subtract the width of any handles or other hardware that protrudes from the door.

For example, if the overall width of a door is 36 inches and there are handles that protrude 2 inches each, then the net width would be 32 inches. When measuring French doors, it is important to take both the overall and net width into account to ensure that they will fit properly in their intended opening.

  • Measure the Door Height

To measure French doors, apart from measuring just the door, you will also have to take into account the space that the door will occupy when it is open. Be sure to measure from the top of the doorframe to the bottom of the doorframe and calculate the average height of the door. 


Once you have all these door measurements, you can determine which size door you need. Remember, however, that internal doors are usually slightly smaller than external doors, so be sure to take that into account when making your purchase. Ensure that the width and height of your door opening at its widest and tallest points. With a little careful planning, you can ensure that your new internal door will fit perfectly in your home.

FAQs on Measuring Internal Doors

  • Can I replace just the interior door without frame?

If you have a standard swinging door, then it may be possible to simply replace the old door. However, if you have a specialised door, such as a sliding door or an accordion door, then it is likely that you will need to replace the frame too.

  • Can I fit an internal door myself?

It is not hard to fit an internal door all by yourself. With just the right tools and a little bit of patience, most people can do this straightforward DIY project easily. However, one might need a helping hand while hanging the door.

  • What are the standard sizes for interior doors?

The standard sizes for interior doors in the UK are 66 inches by 27 inches, 79 inches by 30 inches, and 81 inches by 35 inches. The most common size is 81 inches by 35 inches, which is also the largest size.

  • What is the standard size of a French door?

French doors can vary somewhat in terms of width, but they are typically 80 inches tall. The standard width for a French door is 36 inches, but doors that are 42 inches wide are also available. In terms of thickness, French doors typically range from 1 3/8 inches to 2 1/4 inches.

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Author: Shabana kauser

Shabana Kauser, the Director of Emerald Doors, brings over 20 years of invaluable expertise in the door industry. Her visionary leadership has steered the company to new heights, offering an extensive range of internal and external doors while prioritizing quality and customer satisfaction. The website's glowing reviews stand as a testament to her commitment to excellence. To learn more about Emerald Doors, connect with us on Instagram, Facebook, Twitter, and Pinterest.