Radiator sizing

[nebby]

Evening all, Need to size up a radiator i know there's loads of sites that do it for you but i would like to know how to calculate it on site, i've done it before but can't get it right.

Just wondering if somebody can just show me a quick example to show me how.

Cheers.

 

[andekoch]

it all depends on how accurate you want or need to be since there are a lot of factors that can affect the rad size.
for a quick calc I use a rule of thumb range of 30-50w/m3 (30 for bedroom or hall to 50 for lounge or other room that needs to be warmer).

 

[dontknowitall]

Size of room in metres x 45/1000 (or 40 for well insulated or 50 for colder/3 outside walls, large windows, etc)

e.g. 3.0 long x 2.5 wide x 2.3 tall = 17.25 x 45/1000 = 0.77625 Kw then rounded to e.g. 0.8 Kw - 1.0 Kw.