What BTU radiator do I need?

Choose a radiator with a BTU output that matches the heat loss of your room. Measure floor area and ceiling height, note insulation quality, number of external walls and windows, then use a BTU calculator to estimate required output for your desired temperature. Also check radiator outputs listed in watts and convert if needed, 1 watt equals about 3.412 BTU. If unsure, contact a heating specialist with your room details for a precise recommendation.

How to work out BTU for a radiator?

Work out BTU for a radiator by calculating the heat needed for the room and converting watts to BTU. Measure length × width × height to get room volume in m³, multiply by about 40 W/m³ as a baseline, adjust upward for poor insulation, high ceilings or large windows, then convert watts to BTU by multiplying by 3.412. Alternatively use an online BTU calculator for a quicker result, entering room size and insulation level for suggested radiator output.

What BTU is my radiator?

You can find a radiator’s BTU output on its product specification or by estimating it from the radiator size and room requirements. Check the radiator’s label, user manual or product page for a stated output in BTU or watts, or note the model number and contact the manufacturer. If no spec is available, measure the radiator and use a BTU calculator to estimate required output based on room area, ceiling height and insulation, then match that to the radiator’s measured or estimated output.

Calculators | Radiator BTU calculator

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Radiator BTU calculator

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The heat output or 'BTU' (British Thermal Unit) calculator is a great way to work out how much radiator power you need. There are several factors which can affect this, such as room dimensions, heating levels and types of window, which are all covered in our radiator BTU calculator. Please note: You may need several radiators for bigger rooms.

How do I choose the right radiator?

The BTU value of all our radiators is clearly labelled in-store and online, helping you find those which suit your requirements.

Which room you are heating?

Select a room

What are the dimensions of the rooms?

Length

Width

Height

What type of windows or doors are in the room?

Double glazed doors and windows

French Doors and windows

Your BTU result

BTU

Frequently Asked Questions

What BTU radiator do I need?: Choose a radiator with a BTU output that matches the heat loss of your room. Measure floor area and ceiling height, note insulation quality, number of external walls and windows, then use a BTU calculator to estimate required output for your desired temperature. Also check radiator outputs listed in watts and convert if needed, 1 watt equals about 3.412 BTU. If unsure, contact a heating specialist with your room details for a precise recommendation.
How to work out BTU for a radiator?: Work out BTU for a radiator by calculating the heat needed for the room and converting watts to BTU. Measure length × width × height to get room volume in m³, multiply by about 40 W/m³ as a baseline, adjust upward for poor insulation, high ceilings or large windows, then convert watts to BTU by multiplying by 3.412. Alternatively use an online BTU calculator for a quicker result, entering room size and insulation level for suggested radiator output.
What BTU is my radiator?: You can find a radiator’s BTU output on its product specification or by estimating it from the radiator size and room requirements. Check the radiator’s label, user manual or product page for a stated output in BTU or watts, or note the model number and contact the manufacturer. If no spec is available, measure the radiator and use a BTU calculator to estimate required output based on room area, ceiling height and insulation, then match that to the radiator’s measured or estimated output.