BTU Radiator Heat Output Calculator

>>  What is a BTU?

A British Thermal Unit (BTU) is an approximation of the amount of energy required to heat 1lb (one pound) of water from 39°F to 40°F (degrees Fahrenheit), and is roughly equal to 1.055 KJoules. Simplified, 1 BTU is roughly the amount of heat produced by burning a single wooden match.

>>  How is the required amount of BTUs to heat a room calculated?

First you need to calculate the cubic volume of your room (in feet or metres) by multiplying the height, width, and length of the room (done for you with our free calculator). We then apply further mathematical equations to determine the heat loss in your room (whether that is through the floor, walls, windows, ceiling, or roof) before delivering, what we consider to be, the most accurate guide when selecting a radiator or heated towel rail to heat your room efficiently; this means to a comfortable temperature at the lowest possible fuel costs to you.

>>  What if the radiator I want doesn't precisely match my BTU score?

Don't worry! Although it is true that a radiator with a grossly insufficient BTU output will never heat a room efficiently, and a radiator with a much higher BTU output than required will overheat a room, there is some leeway; we recommend that you go no lower than 10% below the recommended BTU output, but there isn't really any upper limit - one of the great things about radiators is that you can turn them down!

Please remember, it is also possible to combine radiators to achieve a BTU level. Many rooms have more than one radiator in them for this very reason.