BTU Calculator

Welcome to the Salvagedoctor online BTU Calculator.

A radiator must 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 this array of both significant and marginal factors, results from BTU calculators will differ slightly depending upon their emphasis on each.

The result you get on our site will simply be based on the questions asked below whilst using 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.

We hope that you can use it to establish a guide for your radiator sizes and (here’s the disclaimer!) recommend that you seek the advice of a qualified heating engineer if in doubt. Please ensure you fill in all the required fields below entering meters in decimals. i.e.; 1200mm please use 1.2M

You can email the result to yourself at the bottom. Good luck 🙂

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