BTU Calculator

Estimate the towel radiator output needed for a comfortable room.

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Accurate ResultsBased on UK conditions

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1. Room Size

Enter dimensions and window area.

Room Length (m)Length (m)mRoom Width (m)Width (m)mCeiling Height (m)Height (m)m

Window option

Approximate window size

Enter your room dimensions

We'll calculate your room area and volume
to recommend the right BTU for you.

Area 6.0 m2 / Volume 14.4 m3 / Window 1.2 m2

Room Area: 6.0 m²
Room Volume: 14.4 m³
Window Area: 1.20 m²

Towel Radiator Output Guide (UK)

View all

Room Size	Typical Output	Use Case
Small cloakroom	500–900 W	Supplementary warmth
En-suite	700–1,200 W	Main or additional heat
Bathroom	1,000–1,800 W	Main heat source
Large bathroom	1,800 W+	Main heat source

How BTU Works

BTU/h expresses heat output. The calculator converts the required watts into BTU/h and adjusts hydronic radiator catalogue output for the selected operating temperature.

Calculates room size
Adds heat-loss factors
Uses UK design temperatures
Checks radiator output

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Helpful Guides & Advice

Towel Radiator BTU Calculator: How to Choose the Right SizeRead Guide

Why Is My Cistern Noisy After Flushing? 5 Common Causes & FixesRead Guide

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Towel Radiator Output Guide (UK)

Room Size	Typical Output	Use Case	Notes
Small cloakroom	500–900 W	Supplementary warmth	Check wall and window losses
En-suite	700–1,200 W	Main or additional heat	Towels can reduce room output
Bathroom	1,000–1,800 W	Main heat source	Use DT50 correction for cooler systems
Large bathroom	1,800 W+	Main heat source	A heat-loss survey may be needed

How BTU Works

BTU/h expresses heat output. The calculator converts the required watts into BTU/h and adjusts hydronic radiator catalogue output for the selected operating temperature.