[PaulK]

If you look here https://sailboatdata.com/sailboat/catalina-30 and use a pair of dividers on the floor plan you should be able to work it out. You know that the boat is 30’ long, so half of it is 15. Half of that … etc., until you get to a divider-spreading that is around one or two feet. Use that divider-spreading to determine the length and width of each space and you should be able to work out the square footage – roughly.