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Heat Output Calculator

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  • Unsure what size of Stove or Fire you need?
    Try our handy Kilowatt Calculator to give you a rough idea what size of appliance you will need for your room. Please remember that this calculator should only be used as a guide and that a number of factors in your room may alter the actual output that you may require. We recommend you have a qualified person give you a more exact appraisal.
    Heat Output Estimator



    Please note: This form is not suitable for choosing boiler, or gas stoves.


    Instructions for Use

    Select whether you want to base your calculation in metres or in feet.

    Enter your room dimensions into the boxes.

    Click on the "Calculate" button.

    The approximate heat output for your room size will be calculated and displayed.

    Manual Calculation
    (Room Length (m) × Room Width (m) × Room Height (m)) ÷ 12 = Output (kW)

    The figures produced are intended to give an approximate guide only. Please check with a qualified person to ensure you pick the correct kW output for your size of room. The values displayed are based on an outside ambient temperature of -1°C. Please select a slightly higher output than the form suggests to increase heating in colder conditions.

    This page does not provide an exact classification for appliance output, but can be used to give you a good idea. The ability of a stove to heat your room can be affected by other factors which you will need to take into consideration such as a larger than usual number of doors or windows (including patios) in the room, or other draft sources. In these cases you may need to look at a stove with a greater output.

    Building Regulations state that if you install a stove or fire that has a output rating over 5kW a ventilation brick will need to be installed in your room.