Replacing doors made easy.
Whether you are looking to upgrade an existing door, install a bigger door, or create an entirely new entryway, it is imperative that you know how to measure for replacement doors. Depending on the location and door installation, you will need to measure door sizes differently. So it is important you take note of all this vital information to make replacing doors as painless as possible.
In This Guide:
Understanding Door Replacement
Standard Door Measurements
How to Measure for Replacement Doors
Understanding Door Replacement
Sourcing the right door can be tough, particularly because there are so many different types of doors including interior and exterior doors, both of which vary in size. You need to understand how to measure for replacement doors so that you know what you are looking for and are able to buy the right one. The last thing you want to do is make a purchase and end up with an ill-fitting door.
Terminology
Before you can learn how to measure for replacement doors, you first need to understand some important terminology and jargon involved in the process.
Rough Opening: This is the structural opening that is created within the wall by the head at the top, the wall studs at the sides, and the floor or sill at the bottom.
Door Jamb: The door jamb is the surface that runs vertically down either side of the frame. Both the door hinges and the striker plate (which helps you open, close, and lock the door), are situated on the door jamb.
Door Frame/Jamb Frame: This is the wood frame that the door itself hangs from. Door jamb measurements comprise a top jamb and side jambs, and for exterior doors – a threshold. Interior door frames often have narrow strips called stops, nailed within the frame to create the edge that the door closes against. Exterior doors often have jambs with a built-in step that serves as a stop.
Prehung Door: A prehung door comes with hinges and is already attached to the jamb frame. If it is an exterior prehung door, it will have a door sill or frame and trim. Interior doors, however, don't usually have a sill or frame. Whenever there is a trim, it is important to account for that extra amount when measuring a door to ensure a perfect fit. A prehung door is a good option if you are doing an overhaul and fitting an entirely new door and frame.
Door Slab: As opposed to a prehung door, a door slab or door panel is simply one solid replacement door that has no accessories such as hinges, jambs, or other decorative trims. This is ideal if you are looking to replace just the door and keep everything else intact.
Slab Door: A slab door or a slab-style door is a type of door that has plain, flat sides with no panels or decorative features.
Standard Door Measurements
When measuring a door, remember the standard sizing only includes the door panel, not the frame, jamb, or opening. There are many types of doors available including interior, exterior, and entry doors, all of which vary in size. The right door size depends on your needs and specifications, which need to be factored in when selecting the door location, size, style, and building codes.
Standard Interior Doors
When installing replacement doors for the interior of your home (bedroom, bathroom, or passage), you should know that they are usually thinner and smaller than exterior doors. Since they do not have to open to the outside, they are usually left untreated as they don't have to weather the elements. As determined by International Residential Codes (IRC) both interior and exterior doors have to meet standard door requirements. Closets, however, are narrow and don't need to meet those requirements.
Door Frame: A door frame typically measures 1/2 to 3/4 inches narrower and about 1/2 inch shorter than the rough opening. This ensures you have enough room to fit the frame and square it up before fastening it to the framing of the rough opening.
Height: Standard interior doors should be a minimum of at least 80 inches, the same as that of an exterior door. Doors that are 80 inches tall are 6 foot, 8 inches in measurement which is why they are also known as "6/8 doors."
Width:The most common widths for interior doors for bedrooms, bathrooms, and passages, vary between 28 and 32 inches, though there are other sizes available.
Thickness: The standard thickness for interior doors is 1 3/8 inches, but if your door is taller than 80 inches or wider than 36 inches, the recommended thickness increases to 1 3/4 inch.
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Standard Exterior Doors
When it comes to exterior door installation, these models are usually bigger and made of thicker treated wood, as they open up to the outside and need to weather the elements. For sliding doors, the standard width and height can vary, though they do have an average height of 80 inches and an average width of 6 feet.
Height: As with interior doors, standard exterior doors should be a minimum of 80 inches in height. They can go up to 96 inches in standard sizing.
Width:Though exterior doors are usually larger than interior doors, they typically have a standard thickness of about 36 inches. It is possible to find smaller ones in standard sizes of 30 or 32 inches wide.
Thickness: The standard thickness of an exterior door is 1 3/4 inch, thicker than that of an interior door.
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How to Measure for Replacement Doors
Before you shop for your new door you will need to measure for it. Though it sounds simple enough, there is some technique that goes into taking down the correct sizes. Follow these steps for how to measure a door accurately so that you have the information you need to choose the size.
Tip!
It is always better to round down to the nearest inch because a door that's a little smaller will work fine, but one that is too large may not fit at all.
Measure for Door Slab Replacement
The measurements you need will depend on whether you are replacing the frame and hinges as well, or just the door slab. If the frame and hinges are in good condition and you want to keep them as is, you may simply need to know how to measure for a replacement door slab. These measurements are far easier to take as there are no additional features to account for.
Tip!
Before you replace your door be sure to measure your current door frame and not the door to get the correct dimensions for your replacement door.
Width: In order to get the door width, you need to take three measurements on the inside of the door frame. Run the tape measure along the width of the door frame from left to right in three places. Start with the top, the middle, and end with the bottom. The smallest of these measurements will determine the width of the door.
Height: To get the height, you need to measure inside each vertical side of the door frame. The shortest length will be the height. Remember when you measure for the height, you will need to account for any carpeting (for interior) or threshold (for exterior).
Thickness: If you are just replacing the door slab and keeping the frames, you need to ensure that you purchase a door with the same thickness as the current one. To measure the thickness you should run a tape measure along the edge of the door. You should also measure the rebate in the frame – this is where the door sits when it is closed. These measurements should be similar in size, around the standard thickness of 1 3/4 inches.
Additional Measurements: Measuring a door does require a few additional steps to to ensure the perfect fit.
- Measure the location of the three hinges. To do this, measure from the top of the door to the top of each hinge.
- Measure the width and height of each hinge.
- Measure from the top of the door to the middle of the hole for the door handle (bore hole). For the most accurate measurement, it's a good idea to remove the door handle entirely.
- Measure the distance from the center of the bore hole to the closest door edge as well.
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Swing: When you take door measurements, you will also need to take note of the way the door opens. To do this, stand in front of
the door so that it opens outwards away from you. Check to see what side the hinges are on. If they sit on the left, that means the door is a left-hand open away, if they sit on the right, it means the door is a right-hand open away.
Measure for Prehung Door Replacement
Interior prehung doors usually include side and top jambs, but don't have a door sill, threshold, or decorative trim. Exterior prehung doors usually have a four-sided frame with a threshold, many of which include an
exterior trim. How to measure a door to replace with a prehung model will depend on whether you are replacing an existing door or installing it in a space where there was no door before. Any changes will likely require an adjustment to the rough opening size.
Replace an Existing Door
To replace an existing door, first remove any trim so that you can get to and measure the door frame itself.
Width: Place the tape measure on the outer jamb on one side to the outer jamb on the opposite side. Be sure to measure the top, middle, and bottom, and use the smallest dimension as the width.
Height: Run a tape measure from the sill to the upper jamb. If it is an interior door, measure from the floor upward, and from the door sill upward for an exterior door. Do this in three locations and note the smallest figure.
Thickness: Place the tape measure of the inner edge of the side jamb to the exterior edge. To ensure you get accurate dimensions, make sure not to include the outer trim.
Installing a New Door
How to measure a door for a space where there was no door before requires a little more effort. You will need to begin with the rough opening – the space in the wall where the door frame will sit. A rough opening is usually 2 inches more than the door width and 2 1/2 inches taller than the door height. This extra space allows your door and door frame to sit level and square while still offering enough space for the door to expand and contract with the change of seasons.
Width: To measure the width of the rough opening, place the tape on the inner stud on one side and measure along the stud to the other side. Measure the top, middle, and bottom and use the smallest figure as the width.
Height: Measure the height from the floor or the sill to the lower part of the header of the rough opening. Be sure to measure in three different spots and use the smallest figure as the height.
Thickness: For a prehung door, you will measure the thickness of the wall itself and not the frame of the door slab, as there is none. Place the tape measure on the wall of the rough opening and note the dimensions. Use the smallest dimensions on the exposed drywall or sheeting.
Replacing doors isn't all that hard when you get the measurements right and understand the basic anatomy of a door.
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