The International Plumbing Code and the International Building Code specify the required number and locations of plumbing fixtures in buildings. The code also calls out where you cross the line from providing a unisex toilet room to providing separate facilities for men and women. It is important to note that the point where you need two toilet rooms is a result of this requirement for separate facilities before it is a requirement of the plumbing fixture counts.
Unisex toilets are fine for dwelling units and sleeping units.
Separate facilities aren’t required where the total number of occupants is 15 or less.
Separate facilities aren’t required in mercantile occupancies until you have more than 50 occupants.
Unless there is a compelling reason, you need to split the required fixtures equally between the sexes, the location of any fixtures above the requirement is your choice.
An interesting note, the code calls out that required facilities must be free.