Doorway Clearance Calculator

Clear width is not the door width

The most common mistake in checking a doorway is to read the door size off the frame and assume that is the opening you get. It is not. When a door swings open 90 degrees, the door slab itself sits in the opening and blocks part of it, and the stop that the door closes against eats a little more. A door sold as 36 inches can leave a clear opening of only about 33 to 34 inches.

The 2010 ADA Standards call the usable dimension the clear width, and they define it precisely: measured between the face of the open door and the stop, with the door open 90 degrees. The minimum is 32 inches. That number is the one that matters for a wheelchair, a walker or a rollator, not the door size on the box. This calculator takes the door size and subtracts the thickness and the stop to give you the clear width you will have.

The ADA numbers that matter

A doorway has to clear several bars, not just width. The table lists the ones that come up most often for a home or small commercial project.

Width and threshold are the two most people can fix cheaply. Maneuvering clearance is the one that catches remodels, because it depends on the wall and floor space in front of the door, which is not always yours to change.

Worked example: a 36 inch interior door

Take a standard interior door sold as 36 inches wide, 1 3/4 inches thick, with a stop 5/8 of an inch deep. The clear width is 36 minus 1.75 minus 0.625, which is 33.6 inches. That clears the 32 inch minimum with about 1.6 inches to spare, so this door passes on width.

Now the threshold. A typical interior door sits on a floor with no threshold, so that passes easily. But an exterior door with a 3/4 inch threshold would fail the 1/2 inch maximum and would need a beveled threshold or a small ramp. And if the approach is a front pull, you need 18 inches of clear floor on the latch side of the door. A closet door with 8 inches of wall beside it fails that test even though the width is fine.

Maneuvering clearance by approach

Maneuvering clearance is the floor space a person needs to get to the door, open it and pass through, especially in a wheelchair. It depends on which direction you come from and whether you pull or push the door. A front approach means you face the door straight on; a hinge approach means you approach from the hinge side; a latch approach means you approach from the latch side. Pull side is the side the door opens toward.

The rule of thumb is that the harder the reach, the more space you need. A front approach on the pull side is the easiest and needs the least, 18 inches beyond the latch. A latch approach on the push side is the hardest, needing 48 inches, because you have to swing the door away while positioned at the wrong side. The calculator above looks up the number for the approach you pick so you can check it against the space you have.

Thresholds, hardware and force

Width gets all the attention, but three smaller details decide whether a doorway is truly usable. Thresholds come first: 1/2 inch maximum, and anything over 1/4 inch has to be beveled at a slope no steeper than 1:2 so a wheel can roll over it rather than catch. A raised sill at an exterior door is the usual offender here.

Then opening force. Interior hinged doors have to open with 5 pounds of force or less, which is light. A stiff closer or a swollen frame can push a door over that, and the fix is usually adjustment rather than replacement. Finally, hardware. Lever handles beat round knobs, because a knob requires grasping and turning that many people with limited hand strength cannot do. The rules ask for hardware that works without tight grasping, pinching or wrist twisting, and a lever is the simple answer.

Wheelchairs, walkers and real-world fit

The 32 inch minimum is not arbitrary. Most manual wheelchairs are 24 to 28 inches wide and power chairs run up to about 30 inches, so a 32 inch clear opening leaves a couple of inches to spare for a straight pass. That margin matters because nobody goes through a doorway perfectly square, and a small error at an angle eats the clearance fast.

Walkers and rollators are narrower, often 24 to 27 inches, so width is rarely their problem. Their issue is maneuvering: turning a walker through a door in a tight hall needs the same clearance in front of the door as a wheelchair does. That is why the calculator reports both the clear width and the required maneuvering space, since a door can pass one and fail the other.

How to fix a door that fails

If the clear width comes up short, the cheapest fix is often an off-set or swing-clear hinge, which swings the door out of the opening and can add about 1.5 to 2 inches. It is a hardware swap, not a construction job, and it is popular for bathrooms and bedrooms in accessible remodels. Removing an oversized stop helps a little too. If those are not enough, widening the opening means cutting the header and moving framing, which is a real project.

For thresholds, a beveled threshold or a small transition ramp solves most exterior-door failures. For force, adjust or replace the closer. For hardware, swap knobs for levers. The authoritative source for every number here is the 2010 ADA Standards for Accessible Design, and the US Access Board's guide to doors and gates walks through the same requirements with diagrams.

One note before you build to these numbers: the ADA applies to public and commercial buildings, not private homes. For a home, they are a good target for aging in place rather than a legal requirement, and a local contractor or accessibility specialist can tell you what your project needs.