Most door projects go wrong at the tape measure, not in the showroom. Standard door sizes exist to make shopping simple, but the numbers only help if you know which number you are holding. The slab, the rough opening and the clear space you actually walk through are three different measurements, and mixing them up is how people end up with a door that will not close or an opening that will not take a door at all.
Here is the whole system in plain numbers, including the one measurement that almost every size chart skips.
Start with the three numbers that matter
Before any chart makes sense, you need to know what you are measuring.
- The slab is the door panel itself. A 30 inch door means a panel 30 inches wide.
- The rough opening is the framed hole in the wall, stud to stud, before any jamb or trim goes in. It is always bigger than the slab.
- The clear opening is the gap you actually walk or carry furniture through once the door is hung and standing open. It is always smaller than the slab.
Write down which one you measured. A surprising share of ordering mistakes come from someone measuring a rough opening and then ordering that number as a slab size.
Standard interior door sizes
Interior doors run from 24 to 36 inches wide and are almost always 80 inches tall. Height is the easy part. Width is where the real choice lives, and the right width depends on which room the door serves.
| Room | Common width | Height |
|---|---|---|
| Closet or pantry | 24 or 28 in | 80 in |
| Bathroom | 28 or 30 in | 80 in |
| Bedroom | 30 or 32 in | 80 in |
| Primary bedroom | 32 or 36 in | 80 in |
| Hallway or main passage | 32 or 36 in | 80 in |
| Laundry or utility | 28 or 30 in | 80 in |
The most common interior door in American homes is 30 by 80, with 32 by 80 close behind. Taller options exist. Eighty four inches, or 7 feet, shows up in upgraded builds, and 96 inches is used in homes with 10 foot ceilings. Both cost more and are rarely stocked, so expect a wait.
Interior slabs are 1 and 3/8 inches thick. That thickness is the reason hinges, locksets and jambs all interchange so easily, and it is why an exterior door will not simply drop into an interior frame.
One detail worth knowing: residential code sets no minimum size for interior doors. Only the main exit door is regulated. Everything else is convention, which gives you more freedom than most people realize.
Standard exterior door sizes
The front door standard is 36 by 80 inches. If your home was built after 2000, that is very likely what you have.
- Widths: 30 inches for side and utility entries, 32 inches for back doors and many older homes, 36 inches for the standard front door, 42 inches for oversized entries.
- Heights: 80 inches is the baseline, 96 inches is increasingly common in new builds with tall ceilings.
- Thickness: 1 and 3/4 inches, thicker than an interior door because it carries weather, security and insulation duty.
Double doors come in total widths of 60 inches (two 30 inch panels), 64 inches (two 32s) and 72 inches (two 36s). A single door with one sidelite usually totals 48 to 52 inches. With two sidelites, figure 60 to 66 inches.
The code requirement here is narrow and specific. IRC section R311.2 requires every home to have at least one exit door with a clear width of 32 inches and a clear height of 78 inches. A standard 36 inch door clears that comfortably. If you want other numbers that behave the same way, the rise and run limits for stairs are the other place code gets specific about everyday dimensions.
Rough openings: add 2 inches and 2.5 inches
The rule is simple. A rough opening should be about 2 inches wider and 2.5 inches taller than the door slab.
| Door slab | Rough opening |
|---|---|
| 24 by 80 in | 26 by 82.5 in |
| 28 by 80 in | 30 by 82.5 in |
| 30 by 80 in | 32 by 82.5 in |
| 32 by 80 in | 34 by 82.5 in |
| 36 by 80 in | 38 by 82.5 in |
That extra space is not waste. It is room for the jamb, the shims and the adjustment you will need when the floor turns out to be slightly out of level. Framing an opening tight to the slab size is the most common do it yourself framing mistake in this category, and fixing it means opening the wall again.
When you measure an existing rough opening, take the width at the top, middle and bottom, and the height on both sides. Then use the smallest number you got. Walls move, and the door has to clear the tightest point.
The measurement almost nobody checks
Here is the part that most size charts leave out entirely. A 32 inch door does not give you 32 inches of walking space.
Once the slab hangs in a jamb with a stop, and the open door itself sits in the way at 90 degrees, a 32 inch slab leaves roughly 29.5 inches of actual clear passage. You lose about two and a half inches to hardware you cannot remove.
That gap matters in three situations.
- Wheelchair or walker access. Accessibility guidance asks for 32 inches of clear opening measured from the face of the door to the stop. To get a true 32 inches clear, you generally need a 36 inch door.
- Moving furniture. A sofa that needs 31 inches will not pass through a 32 inch door, whatever the label says. Check the clear number. The same arithmetic decides whether a piece can reach a narrow living room at all.
- Aging in place. Specifying 36 inch doors for bedrooms, bathrooms and main hallways costs very little extra while the walls are open, and is close to impossible to add later.
Jamb depth: the detail that stalls installs
Jamb depth has to match your wall thickness, and two standards cover most houses.
- 4 and 9/16 inches for walls framed with 2×4 studs.
- 6 and 9/16 inches for walls framed with 2×6 studs.
If your wall is thicker than the jamb, which is common in older homes with plaster or where someone furred out a wall, you need a jamb extension. That is a cheap and simple fix, but only if you find out before the door shows up on a truck.
Older homes play by different rules
If your house predates 1950, assume nothing. Exterior openings of 32 by 78 and 30 by 78 were common. Interior doors can be narrower and shorter than anything sold today, and some are no longer square because the house has settled around them.
You have three options with a non standard opening.
- Order a custom size. Expect to pay 30 to 50 percent more and wait 6 to 12 weeks.
- Reframe the opening to a standard size. More work up front, a cheaper door, and far easier to replace the next time.
- Keep the existing frame if it is sound and square, and order a slab only.
For a house full of odd doors, reframing to standard sizes during a renovation usually pays for itself the second time you need to replace one.
Prehung or slab: how to decide
A prehung door arrives already mounted in its frame with the hinges attached. A slab is just the panel.
Choose prehung when you are framing a new opening, replacing a damaged or out of square frame, or you are not confident about cutting hinge mortises by hand.
Choose a slab when the existing frame is solid and square, the hinge positions match, and you are simply tired of looking at the old door. A slab costs less and installs faster, but it has to match the old door exactly on hinge layout and swing direction.
A five minute decision path
- Measure the existing slab: width, height and thickness.
- Measure the rough opening at three points across and two points up. Keep the smallest of each.
- Measure wall thickness so you can pick the right jamb depth.
- Decide whether you need a true 32 inches of clear passage. If yes, step up to a 36 inch door.
- Check whether the frame is square and sound. Square and sound means a slab works. Anything else means prehung.
Five measurements, one judgment call. That is the entire job. If you are sizing other openings in the same project, the same habit of measuring the real clearance rather than the nominal size applies to closet depths too.
Frequently asked questions
Is 36 by 80 a standard door size?
Yes, and it is the most common exterior front door size in the United States. A 36 inch slab leaves roughly 33.5 inches of clear passage once installed, which clears both the code minimum and the accessibility target.
What is the most common interior door size?
Thirty by 80 inches, with 32 by 80 a close second. Bedrooms usually get 30 inch doors, while primary bedrooms and accessible bathrooms often get 32 or 36.
What rough opening do I need for a 30 inch door?
About 32 inches wide by 82.5 inches tall. If your 32 inch measurement is the finished frame rather than the rough opening, a 30 inch door will not fit, so confirm which one you measured first.
Can I fit a wider door in an existing opening?
Only by reframing. Widening an opening means moving a stud and usually resizing the header, which is structural work. It is straightforward during a renovation and expensive as a standalone job.
Are 8 foot doors becoming standard?
They are common in new construction with 9 and 10 foot ceilings, but 80 inches is still the baseline. In a house with 8 foot ceilings, a 96 inch door is not an option without major framing changes.
One last thing about cost
Standard door sizes save money mostly because they are already sitting in a warehouse. A standard size often ships in one to two weeks at catalog price. A custom size adds 30 to 50 percent and can take 6 to 12 weeks. So if you are weighing a reframe to 36 by 80 against a custom 33 by 79, the reframe is almost always the better call, and it leaves you with an opening that any future owner can shop for in ten minutes.