Why there is no table here
Accessible parking is civil rights law, and it reaches a lot through more than one document at once: a federal standard, whatever the state has adopted, whatever the local jurisdiction has added, and the conditions written on the permit for this particular site. Those layers do not always agree, the stricter one governs, and which one is stricter is not always obvious. On top of that, the count depends on determinations a calculator cannot make — whether the lot is one parking facility or several, what the building it serves is used for, and whether a change of use resets anything.
A page that printed a ratio would be right in most places and wrong in some, and the people it was wrong for would have no way of telling. So the ratio is a field, and the fields around it name the document each number should come from. What is left is worth having anyway, because the multiplication is where the arithmetic mistakes actually happen: rounding a fraction the wrong way, forgetting that van stalls come out of the accessible count rather than being added to it, or forgetting that shared aisles halve the aisle count but not the stall count.
The frontage is the part that surprises people
Five accessible stalls do not occupy the frontage of five stalls. With the placeholder dimensions on this form, four car stalls at 8 ft, one van stall at 11 ft, two shared car aisles at 5 ft and one van aisle at 8 ft come to 61 ft. Five ordinary 9 ft stalls come to 45. The group is sixteen feet wider, which is most of two more ordinary stalls, and that is before the accessible route and any kerb ramp take their own space.
This matters at the design stage because the accessible group is normally placed nearest the entrance, which is the most contested frontage on the lot. The number to carry into the layout is not the accessible count, it is the frontage, and it comes out of the row rather than being found somewhere else.
Shared aisles, and what sharing does not do
Where pairing is permitted, two stalls face each other across one aisle, so eight car accessible stalls need four aisles rather than eight. Whether pairing is permitted at all, and whether a van stall may be paired, are determinations for your reviewer rather than properties of geometry. Sharing reduces the aisle count and therefore the frontage; it does not reduce the stall count and it does not change any dimension.
Slope, which this page cannot help with at all
A stall and its aisle can be exactly the right width and still fail, because the surface across them is too steep. Slope is measured on the built surface with a level, in two directions, and it is a frequent finding on lots that were striped correctly on paper. Nothing on this page touches it. If the lot is existing, that measurement is the one worth taking before anyone repaints anything, because paint over the wrong grade does not fix the grade.
Questions people ask
How many accessible parking spaces does my lot need?
That is set by law and by your permitting authority for your jurisdiction, and this page does not supply it. Get the ratio from the reviewer, the accessibility plan checker or the design professional stamping the drawing, put it in the field, and the page applies it to your total and shows the rounding.
Are van accessible stalls extra, or part of the count?
In the arithmetic here they come out of the accessible count rather than being added to it, because that is the form most requirements take. If yours works differently, use the direct entry and put in the numbers your plan states. Which applies is a question for your reviewer.
Can two accessible stalls share one access aisle?
Where it is permitted, yes, and the page halves the aisle count when you set it to shared. Whether it is permitted at your site, and whether a van stall may be paired, is a determination for your authority rather than something arithmetic can settle.
Does the page tell me if my lot is compliant?
No. It multiplies the numbers you supply. It does not know your jurisdiction, your site conditions, the accessible route, the slopes, the signage legend or how your reviewer counts the facility. It reports the difference between what is striped and what your ratio produces as a difference, not as a finding.
How much room does the accessible group take out of a row?
More than the same number of ordinary stalls, because of the aisles. With the placeholder dimensions, five accessible stalls with their aisles occupy about 61 ft against 45 ft for five 9 ft stalls. The page reports that difference and converts it into whole ordinary stalls displaced, using the standard width you enter.