Home Radiator BTU Calculator

Estimate your room’s heating requirement in BTU/h and watts. Use the result as a starting point when comparing radiator heat outputs.

1. Room Dimensions

Length * Width * Height *

2. Your Region in the UK

Select Your Region * Your location affects outdoor temperature calculations

3. Wall Information

Number of External Walls * External walls that face outside Wall Construction * Type of construction material used

4. Windows

Number of Windows * Window Glazing Type * Type of glazing installed in your windows

5. Additional Factors

Room Level * Floor level of the room Draught Level * How draughty is your room?

Your Estimated Heating Requirement

BTU Range 0 BTU/hr

Watts Range 0 Watts

View Suitable Radiators

✅ Our Recommendation:

For the best comfort—especially during colder weather—opt for radiator(s) with a total output near the higher end of the suggested range. Having a bit of extra heating capacity gives you flexibility to turn the temperature down as needed, rather than falling short when you need warmth most.

⚠️ Important Notice

This calculator offers approximate results based on common UK conditions and established heat loss calculation principles. The ±15% margin accounts for real-life differences such as insulation quality, draughts, and how well a room retains heat.
For precise assessments, full system design, or projects that must meet Building Regulations, it’s advisable to speak with a qualified heating engineer. They can carry out detailed calculations in line with CIBSE guidelines and UK Building Regulations Part L requirements.