Btu Room Calculator BTU For This Room?

BTU for this room? - btu room calculator

Daugters My room is cold enough, now we are a single panel radiator 700mmx1100mm there was (not) coil.
Room size is as follows:
Width 3.8 m
Length 3m
Height 2.4 m
Two walls - one to the north.
Then heated room (kitchen)
Ceiling above about 170 mm of insulation (in the process of updating it)
Window the 3.5 SQ
Double glazed wood.

Of course I have a heater that is large enough to heat the room, but go online BTU calculator to different answers.

"Can anyone suggest appropriate BTU heat this medium to a comfortable temperature.

Even in the hot load to the attention of 700mm X1100 dual-panel - convector only 5816 BTU / hour, and the panel take odouble Convector 600x1100 only 5115 BTU / hour. Small memory is much less difference, BTU his opinion clear.