Advanced Heat Calculator

1. General information about the room

Enter room name
Preferred room temperature
External winter temperature

2. Heat loss through ventilation

How draughty is the room?

Draughtier rooms lose more heat through 'air changes' than well sealed rooms. The number of air changes is the number of times the air in a room is completely renewed through draughts every hour. Older houses tend to be draughtier than modern houses.

Room usage also affects draughtiness.
Here's a general guide:

  • Select 'Draughty' for hallways and kitchens.
  • Select 'Average' for living rooms.
  • Select 'Not draughty' for bedrooms and bathrooms.

3. Heat transfer through the walls

+ Add wall

4. Heat transfer through the floor & ceiling


Form incomplete
Ventilation heat loss: 0 Watts (0 BTUs)
Fabric heat loss: 0 Watts (0 BTUs)
Total heat loss: 0 Watts (0 BTUs)

Three Tools in One

  • Basic Heat

    Use this heat calculator for a rough idea of how much heat you need. It uses a tried and tested method based on the volume of the room - best for a quick estimate.

  • Advanced Heat Calculator

    Use this for a comprehensive heat loss calcuation that takes into account most parameters that affect heat loss in a room. This method takes a little longer to complete but is fully customisable - you can alter all values.

  • Panel Radiator

    Use this tool to find out how much heat your existing radiators emit. Great if you'd like to replace panel radiators with cast iron radiators!