A circle has to fit in one piece, in one place
The usual mistake is to add up the free floor and conclude there is room. Free floor is not the test. A turning circle is a single disc that has to sit somewhere with nothing in it, and floor scattered in strips along three walls does not add up to a disc anywhere. This is why two rooms of identical area can give completely different answers, and why moving one thing eighteen inches sometimes gains a foot of circle.
The calculator searches the whole floor for the spot where the largest disc fits, then tells you where that spot is. That location matters as much as the diameter. A circle that fits neatly in the far corner, behind the tub, is arithmetically true and practically useless if nobody can get to that corner. Read the centre coordinates and check they are somewhere a person would actually be.
The binding object is rarely the one you expect
The one-at-a-time table is the part of this page worth the most. It removes each object on its own, re-runs the search, and reports what the circle grows to. Most of the time only one or two objects change anything at all, and everything else on the list is irrelevant to the turn even though it is taking up floor.
The gains do not add. If two objects sit on the same side of the room, taking out either one alone may buy nothing, because the other still blocks the same spot, and taking out both may buy a lot. So the way to use the table is iteratively: remove the item that pays, edit the list, run it again, and see what the new binding constraint is. Usually the second run is a different object entirely.
Put the open door in the list
A door leaf standing open is an obstruction, and it is the one people leave out, because on a plan it is drawn as a thin line and a dotted arc rather than as a thing occupying floor. Enter it as a thin rectangle in the position it occupies when open. On a typical interior door that is a strip roughly the width of the door and an inch or two thick, standing perpendicular to the wall it hangs on, and it very often lands precisely where the turning space wanted to be.
The related problem is what the door sweeps on its way, which is a different shape and a different question. The door swing planner handles the arc and works out the angle at which the leaf stops against each thing in the room, and the clear width calculator handles the passage the open leaf leaves in the opening.
One height, one plan, no verdict
Everything here happens at one height, on a flat plan. Real rooms are not like that. A lavatory bowl overhangs its cabinet at one height and nothing at another. A radiator projects six inches at shin level. A wall cabinet takes depth at head height and none at knee height. A windowsill, a towel rail, a grab bar and a light switch all live in this gap between the plan and the room, and the plan is always the optimistic version.
So use the plan answer as a first cut and then check the room at the heights a turn actually happens: at the footplates, at the knees, at the elbows. If those three disagree with each other, the tightest one is the answer. And no output on this page says whether a space is adequate, accessible or usable, because that is not something a page of geometry can determine.
Where the numbers you enter should come from
The turning circle field and the four T-turn fields ship empty, and that is deliberate rather than an oversight. Which figure applies depends on what kind of building this is and which rules govern it — a house somebody is adapting for themselves is not governed the way a rented unit is, and neither is governed the way a building open to the public is, and new construction is different again. The edition adopted where you live matters, and two towns a short drive apart can answer differently.
The people to ask are your building department, an accessibility specialist or the design professional on the project, and for what a particular person needs on a particular day, that person and their occupational therapist. If a rental or a public building is involved, the legal exposure is real and a lawyer licensed in your state is the right call. This page is arithmetic. It has no opinion on any of that and will not pretend otherwise.
Questions people ask
How do I measure the room for this?
Wall face to wall face, at the height the turn actually happens rather than at the floor. Baseboard, a chair rail, a run of surface conduit and a bowed wall all take width that a floor-level measurement misses. Take the length and the width at both ends and in the middle and use the smallest reading for each, because the room is only as wide as its narrowest point. Then measure each object as a rectangle from the same two reference walls, so all the positions share one origin.
The circle fits but only in the corner. Is that any use?
Probably not, and that is exactly why the calculator reports where the centre is. A turning space is only useful where somebody can get to it and where the turn is actually needed, which is usually near the door, near the fixture being used, or between the two. If the largest circle is behind the tub, the honest reading is that the room does not have a usable turn even though the arithmetic found a disc. Enter a smaller region as the room, or add the unreachable zone to the object list, and run it again.
Why does removing a small object change more than removing a big one?
Because a circle is blocked by whatever is nearest its edge, not by whatever is largest. A twelve inch radiator sitting in the middle of the only clear wall can cost more circle than a sixty inch tub filling a corner the circle was never going to use. The one-at-a-time table exists to make that visible, since it is not something you can read off a plan by eye.
Do I include the door leaf and the baseboard?
The door leaf yes, entered as a thin rectangle where it sits when open. Baseboard is better handled by measuring the room between the baseboards rather than between the wall faces, which keeps the object list shorter. Anything that projects only at a height above the turning zone can be left out, but write down that you left it out, because the next person reading the plan will assume the list is complete.
What turning circle diameter should I use?
This page will not tell you, and the field is empty for that reason. The figure depends on which rules govern the building, which edition your jurisdiction adopted, and what equipment is being used, and those differ enough that a number printed here would mislead more readers than it helped. Get it from your building department, from an accessibility specialist or the project designer, and for what a specific person needs, from them and their occupational therapist. Then type it into the field and the comparison appears.