Gas Boiler Size Calculator. An Online Tool that Helps to Save.

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Once there was a pretty common practice to oversize boilers by 25-30%. Today this is regarded as waste, and specifying the models to the home’s right size is of top importance. The size is greatly affected by several factors, including:

  • heat loss calculation
  • house’s size
  • level of insulation
  • airtightness
  • materials used
  • hot water requirements


When you are shopping for a gas boiler, it is of top importance to find the one that your home really needs, and this is when a gas boiler size calculator is going to help you out. If you get a model that is too small, it doesn’t provide enough heat and constantly runs to catch up the needs you have. If you purchase the boiler that is too big, you spend more money than the sum budgeted originally.

gas boiler size calculator

Calculating the square footage of your place helps to choose the heating unit that is optimal from all points of view.

Pluses of Boiler Sizing

Over the last 10-15 years the manufacturing of boilers has developed greatly. Modern models are much more efficient than most of the predecessors. Besides, they are a lot quieter and are able to handle domestic hot water and heating.

Why use a gas boiler size calculator? The thing is it helps to choose the correct size of a boiler to ensure you get enough hot water when you need it. So, the model will meet your current household requirements, cutting down running costs. Calculating should be done carefully, as there is a whole bunch of various factors as well as parameters that are to be taken into account, including the layout of the property, the number of bedrooms and bathrooms, etc.

When the sizing is done carefully, a new boiler runs at higher efficiency, with reduced carbon emissions and lower running costs. The accompanied pluses include lower installation costs. This sounds pretty attractive, doesn’t it?

Calculation Tools

size calculator for gas boiler

There are different online gas boiler size calculators. They require various parameters for identifying the type and the size of boiler your place needs. To the list of the most common ones belong the following:

  • dwelling type
  • window type
  • roof type
  • presence of  extensions
  • outside walls type
  • number of floors
  • internal measurements
  • allowance for domestic hot water
  • number of outside walls


The tool provides a free estimate of the boiler size and potential fuel cost savings. It is especially designed for handling boiler systems both for small and medium-sized residential buildings.

To calculate or check the right boiler size for a definite building without using the rule of thumb, there are various gas boiler size calculators available online. They all can assist. Your task is to choose the one the suits the needs you have.

Examples of online gas boiler size calculators you can find here or here. There are also a lot of types for Android and iOS.

Keep in mind that all figures are approximate, and before deciding consult an expert. This kind of boiler sizing ensures that you don’t overpay to heat your place and assures that your house is heated adequately by a boiler of a proper size.