BTU Calculator

Welcome to the Salvagedoctor online BTU Calculator.

A radiator should provide sufficient output to ensure effective service. Please fill in the required information below to establish the minimum output in Kilowatts (metric measurement) or BTU-British Thermal Units (imperial measurement) your radiator needs to be to heat your given space.

It can be a somewhat exhaustive process determining an exact figure that you actually require, due to the large variety of factors that causing heat loss from your room. Weather patterns and wall coverings are not often factored into calculations but do have marginal effects for example. Variations in window and wall construction will have greater effects. Given the array of significant and marginal factors, different BTU calculators may differ slightly depending upon their emphasis on each factor.

The result you get on our calculator will be based on industry recognised formulas for the heat loss you can expect from each factor. These specific formulas should theoretically be the same from one calculator to another.

Please note that we do recommend you seek the advice of a qualified heating engineer to be sure. Please fill in all the required fields below entering metres in decimals. ie: 2.4 for 2400mm.

Please note: The ‘calculate’ button sometimes freezes.  Please enter all information fields as normal and re-enter the loft insulation field which will in turn re – calculate the result. Otherwise, the calculator is working fine!

Ventilation heat loss:
Heat loss through floor:
Heat loss through exterior walls:
Heat loss through glazing:
Heat loss through ceiling:
Total heat loss + 10%