I found this one online, and has many inputs as to insulation, windows, etc....It states uses Manual J for calcs.http://www.warmlyyours.com/hlc/room/room_general
I ran my living room:
14' x 28'
6 Windows (29" x 60"), Low E, PVC
2 Exterior Walls (8'x14') (R11, clapboard siding/plaster-lathe interior)
Carpet (Unheated basement but with R11 insulation)
overall Insulation - Average
Temp. Location - Buffalo, NY
Outside temp Difference - 0 Degrees, 70 Inside
Came up with approx. 7,777 BTU/Hr heat loss. (Add 20% for error/misc. = 9,332 BTU/hr).
Does that seem in the ball park for that size of a room?
Therefore, 9,332 BTU/hr / (480 Btu/hr at 160 deg. per foot baseboard) = 19 Feet. (I know they use 180, but I want to make sure I have enough if I run at lower temps).