Radiator Sizing Calculator UK
Find the right radiator output for any room. Enter the floor area and choose insulation quality to get recommended Watt and BTU/hr outputs.
How It Works
Required output (W) = area × factor (W/m²).
To convert: BTU/hr = Watts × 3.412.
Default factors are industry-standard: 60 W/m² for well-insulated, 80 W/m² average, 100 W/m² poorly insulated.
Choosing Radiator Types
Column, convector or panel radiators differ in output and style. See our Best Radiators 2025 for comparisons.
Room-by-Room Guidelines
Bedrooms often require lower outputs; bathrooms may need additional capacity for towel rails. Learn more in our Radiator Sizing by Room Guide.
Installation & Balancing
Proper pipe sizing and balancing valves ensure even heat distribution. Follow our Central Heating Installation Guide.
Key Values
| Entity | Attribute | Value |
|---|---|---|
| Radiator | Area | m² |
| Radiator | Factor | W/m² |
| Radiator | Output | W, BTU/hr |
Frequently Asked Questions
What insulation quality should I select?
Good for well-insulated rooms (new builds), Average for typical homes, Poor for solid-wall or uninsulated spaces.
Why convert to BTU/hr?
Manufacturers often list radiator outputs in BTU/hr; conversion helps match specs.
Can I use a custom factor?
Yes—select “Custom” and enter your own W/m² design figure if you have specific guidelines.
How accurate is this estimate?
It follows standard HVAC rules of thumb; consult a heating engineer for precise design.
