I was wondering if there are any general formulas or rule of thumb for estimating how much hot water baseboard or length of each unit is required per square foot of room or which method should be used to calculate how many feet to use. The breakdown per room is what I looking for. Some people have said to run it all along the outside walls, but just seems like overkill to me. Thanks.
yeah they usually say to run it all the way around the exterior walls because it is usually one big long continuous copper pipe. There may not be heating fins on all of it, but unless you want a plumber to bring pipes up here and there, and supply water in multiple locations instead of just one, that's the way it usually works, from what I understand.
To do it right, you would want to run heat loss calculations for each room. A room with many windows will need more heat than a room with no windows. The most important thing is to make sure that the ratios are correct between the rooms so that you don't have any hot/cold rooms.
Running it on all exterior walls seems to be standard practice since most homes are build so that there are no huge heat loss differences between the rooms. Bathrooms and kitchens are a problem for baseboard because the walls are occupied by room components (cabinets, bathtubs, etc).