Ask the hinge before you ask the wall
A doorway loses more width to the door than to the frame. On a standard butt hinge the leaf pivots close to the jamb, so when it stands open the whole slab thickness is parked across the opening. The stop takes another three eighths to a half inch from the other side. Together that is commonly an inch and five eighths off a door that measured fine on the plan, and it is the reason a thirty inch door does not give thirty inches of anything.
Both of those are recoverable without a saw. An offset hinge, sold as a swing clear hinge, carries the leaf out past the jamb line when it opens and returns the slab thickness. An applied stop can be thinned or moved and returns its projection. On the default numbers here the two together are worth an inch and seven eighths, which on many openings is the entire gap between what you have and what you were asked for. Neither needs a permit, neither needs a patch, and neither is available on a fire-rated opening, where the slab, frame, stop and hinges are a tested assembly.
What widening actually costs in width
Taking the wall out is not a proportional trade. Every inch of rough opening you gain becomes an inch of clear passage, so the exchange rate is one to one — but the rough opening is wider than the slab by the hanging gaps, the jamb stock on both sides and the shim space, and all of that has to come out of the wall before any of it reaches the passage. The calculator reports the exchange rate on your own numbers so you can see what the demolition is buying.
| Move | What it returns | What it takes |
|---|---|---|
| Thin or remove the applied stop | The stop projection | An hour, and the door closes differently |
| Offset hinges | The slab thickness | Hardware, and a conversation with the door maker |
| Take the slab off, case the opening | Both, and the door is gone | Privacy, and the door has to live somewhere |
| Widen the opening | Whatever you cut, one for one | Header, permit, patch on two faces, casing, floor |
The patch is bigger than the cut
People budget the framing and forget the finish. A widened opening leaves a band of missing board on both faces, and the patch has to overlap onto sound board past the cut on each side, so a four inch widening becomes a twenty inch patch band twice over, full wall height, with tape and three coats of compound and a paint break that will show unless the wall is painted corner to corner. The calculator carries the overlap you set into the board and tape quantities for exactly this reason.
Under the door there is a strip of floor that was previously inside the wall, which now has to be finished, and there is rarely a matching offcut in the garage. On a wall that used to be a partition and is now an opening, the flooring in both rooms meets in a place it did not meet before, which is a transition question rather than a patching one — the floor transition calculator covers what profile that becomes and how much of it to buy.
Header length is not header size
This page reports how long the header has to be. It does not say what the header should be, and it will not, because the answer depends on what the wall carries, how far it spans, what is above it, what it bears onto and what happens to that load all the way down to the footing. That is work for an engineer or a designer, and on a bearing wall it is a permit and an inspection almost everywhere in the country.
The header depth field ships at zero for the same reason. Leaving it empty makes the cripple count and the cripple length read at their maximum, which is the conservative direction, and it keeps a made-up depth from looking like a specification. Put the real depth in once somebody qualified has given you one and the numbers above it tighten up. Temporary support goes in before the old header comes out. That order is not a preference.
Before anything is opened
Interior walls are where the services run. Supply pipe, waste, a vent stack, a duct chase and cable all live in walls that look empty from the hallway, and the widened band is precisely the strip you learn about by cutting into it. A wall that was furred out at the opening and nowhere else was usually furred for a reason. In a house from before about 1980, the board, the compound, the paint and the flooring beneath may contain asbestos or lead, and demolition is the operation that puts them in the air; whether that applies to yours is a testing question for a qualified assessor rather than a judgement made on site.
None of the arithmetic here decides whether an opening is accessible, adequate or compliant. It gives you widths and quantities from dimensions you supplied. What figure your opening has to meet, and whether it has to meet one at all, comes from the building department for your address, from an accessibility specialist or the designer on the project, and where a rental or a building open to the public is involved, from a lawyer. What one particular person needs to get through a door is a question for them and their occupational therapist, and it is not the same question as what a code table says.
Questions people ask
How much clear width does a swing clear hinge actually give back?
The slab thickness, which on a typical interior door is an inch and three eighths and on a solid exterior door is an inch and three quarters. On a standard butt hinge the open leaf stands edge-on across the opening and that thickness is in the way; an offset hinge carries it out past the jamb line so the passage gets it back. It is the single largest gain available without touching the framing, and it costs a set of hinges. Check with the door manufacturer before fitting them, because the leaf sits differently in the frame and on a rated door it is not permitted at all.
Do I have to widen both sides of the opening?
No, and one side is usually easier. Taking the whole widening out of one side means only one jamb moves, the other stays as a reference, and there is one strip of patching instead of two. Splitting it keeps the opening on its original centreline, which matters when the door is centred on a wall you look straight down, or when something on the far side lines up with it. The framing take-off is nearly the same either way; the patching is not.
Can I widen a bearing wall myself?
This page does not answer that, and the honest version is that the question is not really about skill. A wider opening in a wall that carries anything needs a member sized for the new span by somebody qualified, a load path down through the floor that works, temporary support while the old one is out, and in nearly every jurisdiction a permit and an inspection. Establishing whether the wall is bearing is itself the first job, and it means tracing what lands on it in the attic or the crawlspace rather than judging by what it looks like from the hall.
Why is the drywall patch so much bigger than the piece of wall I removed?
Because a patch has to land on sound board and be taped into it, so it overlaps past the cut on both sides, and it runs full wall height rather than just the height of the opening. Four inches of cut with eight inches of overlap each side is a twenty inch band, on both faces, floor to ceiling. Add the paint break, which will show under a raking light unless the wall is repainted wall to wall, and the finish is usually a larger share of the job than the framing.
What clear width should I be aiming for?
Not something this page will tell you. The target field ships empty on purpose, because the figure depends on which rules govern the building, which edition your jurisdiction adopted, what the opening serves and how it is approached, and a number printed here would mislead most of the people reading it. Ask your building department, an accessibility specialist or the project designer. If a rental or a building open to the public is involved, ask a lawyer as well, because the exposure there is not a building department matter.