Room Heating Calculator
The heating power a room needs is based on its volume and how well it is insulated, expressed in kilowatts (kW) or BTU. Our Room Heating Calculator estimates the radiator or heater output your room requires from the room size and insulation, so you can choose the right size without guesswork.
Room Heating Calculator – what radiator performance do you need?
The Room Heating Calculator above only provides an estimation for the number and sizes of radiators needed. For the calculation we used the following radiator scaling formula:
- X*Y*Z*K=necessary radiator performance in W
The letters of the formula stand for the following:
- X – the length of the room
- Y – the width of the room
- Z – the height of the room
- K – correction factor for 1 cubic metre of air which also takes into consideration the insulation of the building
It is important to know that the calculation run with this calculator does not replace a precise technical plan created by an expert. During scaling, an expert will also take significant technical parameters into consideration. These are for example the type ceiling, the number of heated rooms next to this room, the number and size of windows and the type of heating (in the case of condensing boilers, the performance of radiators needs to be scaled higher because the temperature of the heating water is lower).
Frequently asked questions
How many kW do I need to heat a room?
As a rough guide a well-insulated room needs about 0.07 kW per cubic metre. Enter your room size and insulation for an accurate figure in kW and BTU.
How do I convert kW to BTU?
Multiply kilowatts by 3412 to get BTU per hour. A 2 kW heater is roughly 6824 BTU/h.
What affects how much heat a room needs?
Room size, ceiling height, insulation, the number and type of windows, and external walls all change how much heating power is required.
What size radiator do I need?
Pick a radiator whose output in watts or BTU matches or slightly exceeds the figure from the calculator, so it can comfortably warm the room.
Is it better to oversize or undersize a heater?
A slightly oversized heater reaches the target temperature easily and runs efficiently, while an undersized one struggles. Avoid going far too large, which wastes energy.