What is the square footage of a small/mini hospital or clinic?

I would figure on 10% max for illnesses/ injuries. People who are in a situation like that are probably healthier than the normal population and there is always general quarters isolation if needed.

Good luck with your designs.

On a space station, you need to consider the cubic footage, not the square footage. Ceilings are floors are walls in space and all the surface area of a room is usable for drawers, doors, cabinets, exam areas, etc. You also have to consider, that on a space station, the occupants will probably be mostly healthy young to early middle age adults who have already undergone a large array of tests and diagnostic procedures to assure their fitness for space travel. SO...assuming that you won't be treating 30 people at a time for a bus crash, you can probably figure on roughly a thousand cubic feet (10x10x10 ft (3x3x3 m)) in size to handle all the equipment you'd need. Anyone requiring major surgery would probably be sent down, per some prearranged protocol. The sniffles, muscle aches, eye or ear infections, cuts, etc. could be treated in orbit. You won't need a cat-scanner, mri machine or a full size operating room. Examinations can be done by strapping the patient against a wall, floor or ceiling, wherever there is room. Since putting large structures into space is expensive and building them is just as expensive plus adds the dangers of space construction, any clinic needs to be as small as possible, possibly being used for multiple purposes whenever not needed as a clinic. Forget the high ceilings, expansive floor space and side offices of TV shows and movies like the Star Trek series.

I second the suggestion of looking at submarine design...it is a very close analogy to your situation. You're also going to need to think in terms of "cubic footage," not square footage. In space, it's not the amount of floorspace you have, but the volume of your space. You should also consider that most space habitats are going to have multiple uses. With 100 people, it's likely that there will be many times that you won't have sick or injured patients. Ergo, what other functions can your medical wing serve?

For 100 people, you should have 2 docs, 2 assistants. You'd need a 'general' medical room with a small changing room (a closet, really), and a sterile room for any surgery to be performed, along with an extra 'recovery' room that can be utilized when you have more than the average number of visits. So, figure a small medical office of 8X10, a changing room of 3X4, a surgery room of 10X10, and the extra room , big enough for two bunks, 8x10 as well.

Might be a good idea to look through Submarine & Antarctic station plans.