Calculate Your Heater Size

Calculate Your Heater Size

Use this calculator to quickly estimate the heating requirements for a single room. Please be aware that calculating heat loss is complex, and there are many variables that can affect the final result.

Room Size

Enter the length and width of your room in metres, or click Enter Room Area Manually to enter the total area of your room in square metres.

M
X
M
=
M2
M

Windows

Use the diagram below to estimate the total size of the windows in your room. Include any glass sliding doors in your measurements. Alternatively, click Enter Window Area Manually to enter the total size of your windows in square metres for the most accurate calculation.

X
=
M2

External Walls & Doors

You can enter the number of external walls in your room, or enter the total length of your external walls for a more accurate calculation.

What is an external wall?

External walls are any that connect to the outside or a cold space such as a garage. If you share a wall with a neighbour, this does not count as an external wall.

Or
M

Enter the total number of standard external doors (if any). If you have glass sliding doors, include these in your window measurements instead.

Room Insulation

Select which description best describes the insulation in your room for each interior surface. If you know the exact insulation value (often found in home energy efficiency reports), enter it into the column on the right.

Or
Or
Or
Or