A 25 square foot bathroom is not a bathroom.

Your bathroom seems to be a half bath -=-97 this bath is 18 square foot before vanity cabinet. Unless your bathtub, vanity cabinet (sink cabinet) and linen cabinet are not a part of square feet stated to remodel a bathroom you must have a half bath.

A tub or shower alone is 60 inches wide and just under 3 inches so this coverage is close to 14 square feet alone and thus and does not seem possible in a full bath. You for sure.are not remodeling a large delux master suite bath=-113.

With your small bath there - There can not be room for a large vanity or even room for a regular counter-top. Adding a new pedestal style sink shown in this 35 square feet bath design with out the whirlpool tub=-30 will keep your remodel cost lower and should fit your bathroom design style much better than adding a large decorative vanity=-120 cabinet.

5000 - 7000 dollars is a guesstimate although getting three quotes from local remodeling carpenters is advised - with your local lumberyard as a great source for finding your most reliable bath remodeling contractor.

Wishing you remodeling success!

Depends if you go ceramic or granite for the floor and walls, depends on what type of units you want, ie, shower, tub, or combination, sink, etc.
If you gut the entire bathroom and renovate it you probably could do it for $8,000. including labor.