Sizing a boiler system can ensure that you do not pay too much to heat your home or assure that your home is not inadequately heated by a boiler which is too small. Following a few simple calculations, it is possible for you to gain an appreciation of how much space in your home or office needs to be heated. By working out the area that needs to be warmed, it is possible to work out what size of boiler system you will need.

Measure the dimensions of all of the rooms that need to be heated by the boiler system. Make a note of these on a piece of paper. Make sure you keep a note of which dimensions correspond to which rooms. The average ceiling height of a room is 8 feet. You do not need to measure the height of the room unless you suspect it is greatly different from 8 feet.

Find out what type of insulation you have. If you have modern insulation and double-glazed windows, then the size of heater that you need will be reduced, although if you have old-fashioned insulation and single-glazed windows, the size will increase. Fireplaces with chimneys will also increase the size of boiler needed.

Multiply the dimension of each room to work out its area. A room which is 20 feet by 20 feet will have an area of 400 square feet. Do this for all the rooms in the house or office you wish to heat until you have a total area. Find the square root of this to the nearest whole number (it doesn't need to be completely precise), to give average width and length of each room. Enter this into a BTU calculator (see Resources for a free online calculator) and press "Calculate."

Use the results of this to guide you in selecting your boiler. The BTU calculator will give you a minimum and maximum, which will allow you to work out the range into which your boiler should fall.