BTU Calculator

FIND YOUR PERFECT BATHROOM RADIATOR

Calculate your bathroom BTU requirements to:

Create an inviting bathroom space
Improve heating efficiency
Positively impact fuel bills

How do I choose the right bathroom radiator?

A BTU is a "British Thermal Unit" and it is the unit by which to measure your bathroom radiator's efficiency. As with any other room of your home, to accurately heat your bathroom space, you must consider factors such as wall materials, window size and room dimensions. You can use our BTU Calculator to work out the heating requirements of any room. Simply enter the measurement details and other information into the fields below, and we'll let you know just how many BTUs you may need to heat your room efficiently.

How do I calculate BTUs for rooms in my home?

The best and most accurate way to get our BTU calculation is to ask your local plumber. That said, the Big Bathroom Shop BTU calculator can offer a good guideline for the level of heat output you need to adequately heat your chosen room. Please note: The figure that is calculated will be for the combined output of all radiators/towel rails in the room and some larger spaces may require more than one appliance.

Calculate your BTUs

Room Dimensions

Metric (metres) Imperial (feet)

Width (m) *

Height (m) *

Length (m) *

Window Area X² (Multiply height by width): *

If your room does not have a window, please enter '0' in the field below & select 'no window' in the relevant field below

Room Information

Room type: *

Which space are you heating?

What is below the room? *

Is there a room below? What type of flooring is it?

What is over and above the room? *

Another heated space? Insulation? Where appropriate choose insulation type.

Choose the type of external wall: *

This can help calculate the heat loss of a room

Choose window type: *

This also helps understand a room’s heat loss

How many external walls? *

Reset

Your Requirements

BTU's Required

Watts Required

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What is a British Thermal Unit?

A British Thermal Unit is the approximate amount of energy that is needed to heat a single pound (1lb) of water from 39F to 40F. It’s about the same as the amount of heat needed to burn a single safety match from one end to the other.

How are room BTU requirements calculated?

The required BTU for any room is determined by the cubic volume of the space. That is the length, width and height that’s then multiplied by four – alongside what is above, below and to the side of the space. With this information, our BTU calculator can ascertain the expected heat loss for your room and supply you with a BTU output figure that will heat your space effectively and efficiently.

Why do I need to calculate the correct BTU output?

Determining the correct BTU calculation is an important part of heating your home. Radiators and towel rails with inadequate heat outputs will mean your home never reaches a comfortable temperature. And, choosing one with too high an output could mean you pay over the odds to heat your home. The right BTU calculation should allow you to balance the heat in any room of your home and ensure you have lower bills and suitably warm spaces.