Please see our stove size calculator. This will use your room dimensions to calculate the correct size stove or fire for your room. It is also worth taking into account some other aspects of your home. Reasons for a larger output stove: If you have an older draughty property, you have higher than standard ceilings, you have stairs out of the room, you have limited other heating in the property, if you are going to use the stove every day. Reasons for a smaller output stove: You have a new well insulated property or you only want to use the stove occasionally when it is cold