To measure a rough opening for an interior door, add 2 inches to the door’s width and 2.5 inches to its height. This gives enough space for the door frame, shims, and adjustments during installation. For example, a standard 30″ x 80″ door needs a 32″ x 82.5″ rough opening.
Getting this right up front avoids headaches like buying the wrong door size, forcing it into an uneven opening, or dealing with costly frame fixes later—especially in older homes or during remodels where nothing is quite square.
In this guide, I’ll walk you through the exact steps to measure an interior door rough opening, explain how different door types (like pocket or French doors) change the sizing, and highlight common mistakes to avoid—so your new door fits the first time without frustration.
What Are Standard Sizes for Interior Door Rough Openings?
Interior doors come in a range of standard sizes, but your rough opening needs to be slightly larger than the door itself to make room for the frame and shims. In most cases, you’ll add about 2 inches to the width and 2.5 inches to the height of the door to determine the correct rough opening. Here’s how that looks for different types of doors.
Single Doors
For a basic single interior door, add 2 inches to the width and 2.5 inches to the height. So, if your door is 30 inches wide and 80 inches tall, your rough opening should be 32 inches wide and 82.5 inches tall.
Double Doors
Double doors follow the same rule. Measure the total width of both doors, then add 2 inches. Add 2.5 inches to the height. For example, a pair of 30-inch-wide doors (60 inches total) would need a 62-inch-wide rough opening.
French Doors
French doors require a similar calculation. Measure the width of one door, double it, then add 2 inches. Add 2.5 inches to the height. A pair of 30-inch-wide French doors would need a 62-inch-wide by 82.5-inch-tall rough opening.
Sliding Doors
Sliding interior doors don’t have a one-size-fits-all formula. Instead, measure the actual space between the studs (width) and from the floor to the header (height). If you’re replacing an old door, measure the existing opening directly.
Pocket Doors
For pocket doors, the rough opening needs to accommodate both the door and the in-wall track system. The width should be twice the door width plus 1 inch, and the height should be 2.5 inches taller than the door. So for a 30-inch-wide by 80-inch-tall door, you’ll need a 61-inch-wide by 82.5-inch-tall opening.
How Do You Measure Indoor Door Rough Openings?
Getting an accurate rough opening measurement is key to choosing a door that fits properly and installs without issues. Here’s a step-by-step guide to help you get it right the first time.
Step 1: Measure the Width
Use a tape measure to check the width of the opening from stud to stud. Take three measurements: the top, middle, and bottom, which will account for any bowing or shifting in the wall. Use the largest of the three.
Step 2: Measure the Height
Measure from the subfloor (not finished flooring) to the bottom edge of the header on both sides of the opening. Again, take multiple measurements and go with the tallest.
Pro tip: If you’re adding new flooring, subtract the finished floor height from your total measurement to avoid clearance issues.
Step 3: Check for Square
Measure diagonally from top left to bottom right, then from top right to bottom left. If the numbers match, the opening is square. If not, you may need to adjust the framing or use shims during installation.
Step 4: Measure the Wall Depth
Measure the full thickness of the wall from drywall to drywall. Most interior walls are framed with either 2x4s (for a 4 9/16″ jamb) or 2x6s (for a 6 9/16″ jamb). Getting the right jamb depth helps the frame sit flush with the wall.
Step 5: Account for Door Swing
Make sure there’s enough room for the door to open fully without hitting nearby walls or furniture. Also, check that the swing direction (left or right) makes sense for the space.
Standard Sizes for Interior Doors
Most interior doors come in a handful of standard sizes that make shopping and installation easier. The most common widths are 30 inches (2/6), 32 inches (2/8), and 36 inches (3/0), while standard heights are typically 78 inches (6/6) or 80 inches (6/8). Bi-fold doors usually range from 24 to 36 inches per panel, depending on the opening and design.
If your rough opening doesn’t fit a standard size (this is common in older homes or custom builds), you can always order a door to fit. Just keep in mind that custom doors tend to cost more and may have longer lead times.
Tips for the Perfect Fit
Measuring the rough opening is step one—installing the door so it fits right and works smoothly takes a few more considerations. Here’s what to keep in mind before you buy or install:
Leave Room for Shims
Always make the rough opening slightly larger than the door frame. This gives you space to shim the door plumb and level during installation. Skipping this step can lead to a crooked door that sticks or won’t close properly.
Match the Jamb Width To the Wall Thickness
Use the right jamb size for your wall framing. 2×4 walls typically need a 4 9/16″ jamb and 2×6 walls usually need a 6 9/16″ jamb. An incorrect jamb width will leave your frame sticking out or recessed, which looks sloppy and can affect trim installation.
Plan Around Flooring
If you’re installing new flooring—especially tile or hardwood—factor in the finished floor height when measuring the rough opening height. Otherwise, your door could drag or not clear the floor.
Know Your Local Codes
Some rooms, like bedrooms or bathrooms, may have minimum door width requirements under local building codes. Double-check before ordering, especially if you’re working on a remodel or addition.
Check the Door Swing Early
Before buying, decide on the door swing (left-hand or right-hand, in-swing or out-swing). The wrong swing can make a door awkward to use or interfere with furniture or fixtures.
Measure More Than Once
Use the golden rule: Measure twice, cut once. Even a half-inch mistake can mean the difference between a quick install and a frustrating rework.
Inspect the Existing Frame
If you’re replacing a door but keeping the existing frame, check it for damage, warping, or misalignment. An out-of-square frame can make installing a new door a real headache.
Check Wall Alignment
Walls aren’t always perfectly straight — especially in older homes. Use a level or straightedge to spot bows or bulges that could interfere with the door frame or trim.
When To Call a Pro
While measuring a rough opening is usually simple enough for a confident DIYer, there are times when it’s smarter to bring in a professional. If the opening is out of square, the walls are load-bearing, or you’re working with a more complicated setup like a pocket or sliding door, hiring a pro can help you avoid costly mistakes. The same goes if you’re unclear on local building codes or planning a large-scale remodel. An experienced installer can make sure the job’s done right, especially in situations where precision matters or the framing needs adjustment.
Final Thoughts About Interior Door Rough Opening Sizes
Getting your measurements right from the start is the key to a smooth, hassle-free door installation. Always allow space for the frame, shims, and any new flooring, and make sure your jamb depth matches the wall framing. Take your time, double-check your measurements, and think through how the door will swing in the room. If anything seems off — uneven walls, questionable framing, or strange dimensions — don’t hesitate to ask for help. A small bit of expert advice up front can save you a lot of trouble down the road.