Online heating Calculator

[jpm]

I know there a few of these online I think this is a good one.
Heating Calculator

 

[alph250]

Not bad, but iw ould say its a bit on the arse cover side of sizing

i.e.
for a 16 m2 room with 2 external walls, 2 windows totalling 6m2 with good insulation it works it out to be around 120 watts/m2 which is a bit excessive i would say in a home around 90 - 100 watts would be more than sufficient, BSRIA reckons for a new build around 60 - 80 watts/m2 but then thats with the latest u values etc.

Still not a bad tool!