

Boilers use gas to create steam heat in a home.

Boilers use gas to create steam heat in a home.

Gas boilers use natural gas or propane to heat water to its boiling point. The resulting steam is transferred through pipes in the home, feeding individual radiators in each room. Boilers offer an alternative to traditional forced-air furnaces, particularly in areas of the country where the air is dry. When shopping for a gas boiler, you want to find one that fits the needs of your home. Buying a boiler that is too small will not provide enough heat and will constantly run to catch up to your needs. Purchasing one that is too big may be more expensive than you originally had budgeted. Calculating the square footage of your house can help you choose the optimal heating unit.


Measure the square footage of your home. When you built or purchased your home, you likely were informed of the house's size. If not, you will need to measure each room in the house. Start in the corner of one room and measure the two walls that meet at that spot with a measuring tape. Record the dimensions on a piece of paper.


Convert the each wall length to inches. For example, if your room is 10 feet long on one side by 8 feet, 3 inches on the other, multiply 10 by 12, as there are 12 inches in one foot, to get 120 inches. Multiply 8 by 12 and then add 3 for a total of 99 inches. To calculate the square inches of the room, multiply 120 by 99 for a total of 11,880 square inches. Record this number.


Repeat the first two steps for each room of the house.


Convert your measure to from square inches to square feet. To determine this measure, divide the total number of square inches by 144, or the number of inches in square feet. For example, if your total was 158,950 square inches, your house is 1,103.819 square feet.


Calculate the number of British thermal units, or Btu, required to heat your house. NJ Mechanical estimates that your heater should produce roughly 50 Btu per square foot to be effective. Multiply your square footage by 50 to determine the size of your boiler. For instance, if you house is 1,103 square feet, your heater should be at least 55,150 Btu.

Things You Will Need

  • Measuring tape
  • Notepad
  • Calculator


  • The calculation provides a ballpark figure. How well your home is insulated and the heat loss that occurs in the home over time are other variables that determine exactly what size boiler you need.

About the Author


Photo Credits

  • Jupiterimages/liquidlibrary/Getty Images
Suggest a Correction