Whether you’re upgrading the doors of an interior space or remodelling the entryway to your house, maintaining accuracy in the measurement is key to saving time and energy during the entire door installation process. To measure the required space for a door during the door installation process, you have to have a clear idea about the door rough opening. Getting the appropriate door rough opening size can be very frustrating and confusing for the first time. So, what is actually door rough opening, and why it is important during the installation of doors?
The door rough opening includes the necessary dimensions and structural elements required to install a door properly. Therefore, before you purchase a door for your interior space or the entryway, you have to accurately measure the rough opening for the door. Otherwise, you might face an issue to fit the door into the available space. However, it’s really easy to measure the rough opening size for a door. You only need to add an extra 2” to the actual width of the door and 2 ½” to the actual height of the door to get the measurement for rough openings. Therefore, this measurement of rough opening provides the space for the door itself, as well as the door frame. Now, you can measure and frame the rough opening for the door properly.
Rough Opening for Different Door Sizes
Different homeowners prefer different door sizes for the interior and exterior doors. If you have a door that is 30” in width and 80” in height, the rough opening for your door would be 32″x 82 1/2″. Let’s take a look at the following rough opening chart for different door sizes.
| Door Rough Opening Chart | |
| Door Size | Rough Opening |
| 24″ x 80″ | 26″ x 82 1/2″ |
| 28″ x 80″ | 30″x 82 1/2″ |
| 30″ x 80″ | 32″x 82 1/2″ |
| 32″ x 80″ | 34″x 82 1/2″ |
| 34″ x 80″ | 36″x 82 1/2″ |
| 36″ x 80″ | 38″x 82 1/2″ |
| Door Rough Opening Chart (in feet) | |
| Door Size | Rough Opening |
| 2/0 | 2/2 (in feet) |
| 2/4 (in feet) | 2/6 (in feet) |
| 2/6 (in feet) | 2/8 (in feet) |
| 3/0 (in feet) | 3/2 (in feet) |
Different Types of Doors and Their Rough Openings
Even though the above rough opening chart helps you to measure the rough opening for different doors, there are some exceptions. Therefore, it’s better to understand different types of doors and the calculation of rough openings for those doors.
Single Door
For a single door of 2/6 x 6/8 size, the rough opening is 2” wider and 2 ½” taller compared to the actual size of the door. Therefore, the rough opening for a single door is 32” x 82½”.
Double Door Unit
The formula of rough opening for the double door is the same as the single door. Therefore, to calculate the double door rough opening, you have to add 2” in width and 2 ½” in height.
Double Door Unit with Astragal
In the case of rough opening for a double door unit with astragal, the formula is to add 2 ½” in both width and height. Therefore, if the size of the door is 5/0 x 6/8, the rough opening for this door is 62 ½” x 82 ½”.
French Door
The calculation for a French door rough opening is different from the other doors. Here, for the width you have to multiply the width of the door by 2 and then add 2” to that and for the height, you have to add 2 ½”. Therefore, the rough opening for a French door of #0” x 80” is 62” x 82 ½”.
Sliding Door
There is no formula to measure the rough opening for a sliding door. Here, you have to take manual measurements by using a measurement device. For width, measure the length from stud to stud and for the height, measure the length from the bottom to the head jamb.
Why Is the Rough Opening Size Always Bigger than the Actual Door Size?
There are multiple reasons why we need a bigger size for the rough opening compared to the door size-
- First of all, the bigger rough opening size gives us room to adjust the frame and the door. The extra space is necessary to plumb, square, and level the door during the installation process. For this reason, wall framing is also known as rough framing.
- Secondly, different manufacturers make doors of different sizes. Therefore, when you leave an extra space, you get the room to fine-tune the door. On the other hand, when you do not leave any extra space or the rough opening is too tight, your door might not function appropriately.
- Another important reason for having a bigger rough opening size is that the walls expand and contract in different seasons. Therefore, the bigger rough opening size will offer a certain space for the walls to expand and contract. When the humidity level is high, the walls tend to expand by absorbing moisture. Conversely, when the humidity level decreases, the walls tend to contract. Even though the expansion and contraction occur in a very small amount (less than 1/16”), we need to consider this to help the door accurately function.
- Lastly, a bigger rough opening size is crucial to manage the manufacturing faults.
Standard Door Sizes
When you know the standard door sizes, you can easily and rightly calculate the rough opening size for the doors. So, let’s learn about the standard sizes for the width and the height of a door-
- Standard Width Sizes for a Door:
There are three standard sizes for the width of a door, such as 2/6 (30”), 2/8 (32”), and 3/0 (36”).
- Standard Height Sizes for a Door:
There are two standard sizes for the height of a door, such as 6/6 (78”) and 6/8 (80”).
Manual Measurement for the Door Size and the Rough Opening Size:
Here’s how to measure a door easily:
Height:
Take your tape measure from the top of the door to the bottom. Only measure the door itself. If it’s an old door and there are differences in height, go with the tallest measurement.
Width:
Measure from one side of the door to the other, just the door, not the weather-stripping. If your door is old or not a perfect rectangle, measure in a few places and use the widest measurement.
Thickness:
To find out how thick the door is, put your tape measure on the edge of the door or the door frame (called the jamb). Usually, doors are about 4.4cm or 1.75 inches thick.
Once you have accurately measured the size of the door, you can get the measurement for the rough opening size by using the above-mentioned formulas. In most cases, you only have to increase the width of the door by 2” and the height of the door by 2 ½”.
Frequently Asked Questions:
While the RO size remains the same in all standard indoor doors. The calculation for the rough opening size differs in some special types of doors, such as French doors, sliding doors, and atrium doors.
The rough opening width for most standard interior and exterior doors is typically the same. However, there can be variations in the height between the two. Therefore, it is better to ask the manufacturer for the recommended RO.
To address an oversized rough opening, a straightforward remedy is to add a 1×3 furring strip on one or both opening sides.
If the space at the top is too big, put a 1 x 3 block on the door frame’s upper part. Then, you can attach the bracket to this block.
If your wall is mostly standing upright and your door fits nicely, you’re in luck! You can go ahead and use those brackets. Look for the single arrow markings on them; these arrows guide you to place the screws right on the outer edge of the wall. That’s where the drywall is, so you can make small openings there to fit the screw heads. Easy peasy!
