Bathroom Radiator Buying Guide: Sizing & Steel Tips UK

A bathroom radiator has two jobs: heat a small, damp room quickly and dry towels properly. Get the choice wrong and you end up with a chilly room after the shower, or a rail that rusts. These are the rules of thumb worth following before you buy.

Sizing: do not trust a quick calculator

Heat output is measured in BTU, and the number you need depends on far more than floor area: wall type, window size, ceiling height, whether the room is above an unheated space, and how warm you want it. Radiator experts quoted by Ideal Home warn that many online BTU calculators are not fit for purpose because the calculation needs a lot of inputs. Use a calculator as a rough guide, then check the figures with your installer or heating engineer.

If no model matches your required output exactly, the same guidance is to go for the next size up rather than settle for too little heat. A slightly oversized radiator on a thermostatic valve can be turned down; an undersized one can never do more.

Why material matters in a wet room

Bathrooms are humid, so corrosion resistance counts. Stainless steel is a popular choice because it is rust-proof, durable and retains heat well, according to the same Ideal Home guide. Polished or brushed stainless suits modern bathrooms, while chrome and anthracite mixes suit those who want a bit more colour contrast.

Towel rail or radiator?

If wall space is tight, go vertical: a tall, narrow towel rail gives you more heat output per centimetre of floor and somewhere to hang towels. If you need to heat a large bathroom, a wider panel-style designer radiator gives you more surface area. Consider mounting height, too, so towels can hang clear of the floor and the rail is not in your way when you open the door.

If you like the sound of a vertical rail, our Designer Towel Rails range includes polished stainless steel and chrome and anthracite finishes. For wider wall space, browse our Designer Radiators.

A quick checklist

Work out the room's heat requirement before you fall in love with a design. Pick a rust-proof finish for a wet room. Check your pipework position and valve type, since moving pipes adds cost. Then compare styles and finishes at Ultra Bathroom once you know the size you need.