BTU Calculator

Calculate the required BTU output for your room

Room Dimensions

Width * metres

Length * metres

Height * metres

Window Information

Window Area * Calculate by multiplying window height by window length square metres (m²)

Window Type * This helps determine the expected heat loss

Room Information

Type of Room * Where are you heating?

What is below the room? * Think about the flooring of your room

What is above the room? * Choose the amount of insulation where applicable

Wall & Structure

Type of Outside Wall * This helps calculate how much heat the room might lose

Number of Outside Walls *

Your Required BTU Output

Required BTU

BTU/h

Required Watts

Watts

💡 Recommendation: We recommend choosing a radiator within a 10% range of your calculated BTU requirement. If choosing between a smaller or larger radiator, it's always better to select a larger one and adjust the temperature down, rather than a smaller one that cannot provide enough heat.

⚠️ Important Notice

This calculator provides estimated values based on typical UK conditions and simplified heat loss calculations. Results are calculated using the Delta T50 (ΔT50°C) standard, which is the UK industry standard for radiator outputs.

For accurate heat loss calculations, professional system design, or installations requiring Building Regulations compliance, please consult a qualified heating engineer who can perform detailed calculations following CIBSE standards and UK Building Regulations Part L.