This radiator size calculator will help calculate the correct radiator size heat output (in BTU and KW) when designing a new central heating system or adding rooms to an existing system
This radiator calculator tool will help you in getting the correct heat output for your radiators
A common preferred temperature is below but obviously this varies depending on personal preference
Most of the online radiator calculators, including this one, use various factors to estimate the required radiator size heat output (KW and BTU). They provide a good estimate of required BTU output and a useful check on figures your heating engineer may be specifying in a quote.
They are limited by the factors they take into account