How To Measure An Interior Door: 4 Steps (Do This!)

There are lots of things in a home that we never give much thought or take for granted. Interior doors are some of them. They play a crucial role, enhancing our privacy and putting some space between other family members and us. Yet, we only come to think of them when we have to replace them. Measuring an interior door for replacement sounds tricky, but it is easier than you think. This guide will teach you how to measure your interior door in four quick steps. 

How To Measure An Interior Door

Measuring to replace an interior door only requires a tape measure and pencil and paper. A stepladder or a solid chair may also be useful for easier reach. Tools in hand, here’s how to measure your door in four steps.

1. Measure The Door Slab

If you’re unfamiliar with door lingo, a door slab is a solid panel of wood (or another material) attached to accessories such as hinges, jams, and decorative trimming. Knowing the door slab size is useful if you only want to upgrade the door, not the jambs or frame. 

To find out its size, you have to measure the door slab width, height, and thickness. 

Take the width measurements

For a correct measurement, you have to take the width measurement in three different spots – generally, at the top of the door, in the middle, and at the bottom.

Close the door and stand behind it. Place the tape measure on the door and measure from top left to top right. Record the number on the piece of paper. Now, do the same measuring in the middle of the door and at the bottom. 

Standard, store-bought doors and those made of glass or metal generally have the same width in any spot. However, the width may vary between the spots in the case of custom-made or older doors. If that’s the case, use the largest number when choosing the new door.

Take the height measurement

With the door still closed, place the tape measure on the top of the door (the door slab itself, not the frame or trim) and run it down to the bottom. Record the number. 

Like the width, the height can vary from one spot to another. Thus, you should measure in at least two different spots. Consider the longest dimension for accurate height measurement.

Take the thickness measurement

You can now open the door and place the tape measure on the edge of the door, near the middle. Measure the thickness and write down the number. If the door is old, you might want to measure in different spots for an accurate reading, including the top and bottom of the door.

Once you have all measurements, you can replace the door slab with a new one that will fit perfectly in the frame.

2. Measure The Internal Door Frame 

Measuring the door slab alone is generally enough to find a good replacement. However, if you have an older door, measuring the internal door frame rather than the slab could help you find a perfect fit.

When sizing the door frame, you have to consider the same three measurements: height, width, and thickness.

To measure the height, place the tape measure on the floor and run it up to the lower part of the door’s upper trim

Measure in at least two spots (preferably three), and consider the longest dimension for picking the right door slab.

For the thickness, place the tape measure on the inner side of the door frame at the top of the door and measure to the opposite inner side. Do the same in the middle and at the bottom of the frame, and use the widest dimension when picking the door slab.

As far as the thickness is concerned, measure from the inner area of the frame to its outer area in three different spots. Use the largest dimension. 

3. Measure The Interior Door Jamb

The door jamb is the vertical side of the door frame that holds the hinges on one side and the latch recess and strike plate on the other side. 

One thing to remember is that a door jamb is always part of the frame, but the frame also comprises other elements. 

For measuring the interior door jamb without removing the trim, open the door and measure the distance between the inner sides of the trim or molding. It is always a good idea to take the measurement in three different spots, as explained above.

If you want to remove the trim, measure from the outermost portion of the frame to the other side in three different spots.

4. Measure The Rough Opening Dimensions

If you’re carrying out major renovation works and want to replace the entire door, frame and all – or if you’re installing interior doors in new construction – you have to measure the rough opening (the door opening without any frame or hinges installed). 

Measuring the interior door rough opening is as easy as measuring a door slab. Take the height, width, and wall thickness measurements in three different spots to determine the perfect dimensions for the door frame. 

Most home improvement stores sell interior doors with or without frames. For a perfect fit, we recommend buying an interior door with a frame if you want to replace everything or install a door for the first time. 

Alternatively, you should only buy the door slab after the frame is installed and measure the frame and door jamb to determine its right size.

What size interior door do I need?

Interior doors generally have standard sizes, but you must make sure they comply with the building code requirements

According to the code, standard interior doors must have a height of 80 inches (6’8”) and a width of at least 32 inches measured with the door opened at 90 degrees from the closed position. You should also pay attention to the door swing, which must be at least 90 degrees from the closed position (unless you’re opting for sliding doors). 

This standard dimension also complies with the Americans with Disabilities Act (ADA), meaning the door is wide enough to allow people using wheelchairs to pass through.

Closet and utility doors may have smaller sizes. In this case, the building code allows you to use shorter doors with a height of 78 inches. Their width can vary from 24 to 30 inches (most standard sizes include 24”, 28”, and 30” wide doors). However, all interior doors must have a height of at least 78 inches and a width of a minimum of 24 inches. 

The standard thickness of a door is 1 3/8 inches, but the code doesn’t specify a standard thickness. Thus, you can install thicker or thinner doors based on the thickness of your walls.

While most standard interior doors comply with the dimensions above, some design doors or French doors can be wider – generally 34 or 36 inches wide.

Measurements For Door Sizes

Because most interior doors have a standard height (80 inches), manufacturers and retailers only use the door width to classify the doors they make or sell. Thus, if your door has a standard height (determined through your measurements), you can only use the width to determine which door size to get. The tables below can make things easier.

Door Size To Order Based On Existing Door Measurements 

Existing door widthDoor size to order
23.5” – 24”24”
25.5” – 26”26”
27.5” – 28”28”
29.5” – 30”30”
31.5” – 32”32”
33.5” – 34”34”
35.5” – 36”36”

Door Size To Order Based On Rough Opening Measurements 

Rough opening widthDoor size to order
25.75” – 27”24”
27.75” – 29”26”
29.75” – 31”28”
31.75” – 33”30”
33.75” – 35”32”
35.75” – 37”34”
37.75” – 39”36”

What is the most common interior door size?

The most common interior doors have a height of 80 inches and are 32 inches wide. The most common thickness is 1 3/8 inches

Most French doors have a size of 80 by 36 inches, although older homes may have wider French doors. 

Closet and utility doors are typically shorter and narrower, but they can’t be smaller than 78 by 24 inches (although you may find narrower doors in older homes). 

How do you read door sizes?

Reading door sizes can be confusing, mostly because manufacturers express the size in numbers like 2868 or 3068. What does that mean, anyway? 

To make things easy, remember that the first two digits refer to the width of the door, expressed in inches. The last two to its height, expressed in feet

Thus, a 2868 door is a 28-inch wide door with a height of 6 feet and 8 inches (80 inches). A 3068 door has a height of 6 feet and 8 inches and a width of 30 inches. 

When referring to the height alone, many manufacturers and retailers would call it a 6/8 (read six-eight) door, based on the door’s height in feet (6 feet and 8 inches). 


Measuring an interior door isn’t complicated. However, it is crucial to take your time and take the dimensions in different spots for an accurate measurement. We hope this guide can help you measure your interior door slab, frame, and rough opening so that you can figure out the right door size.

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