Free tool
BTU Calculator (Radiator Sizing)
Estimate the heat output your room needs - then get a quote with your full calculator summary sent to our engineer.
Instant estimate
Your room
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Higher ceilings increase volume, which increases required output.
Insulation affects heat loss, which impacts required BTU.
More exposed walls usually means more heat loss.
Count windows / large glazed doors.
Estimates only. For accurate sizing, a proper heat-loss assessment is recommended.
Your recommendation
Recommended output
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Suggested range
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A sensible sizing window
Heating driver
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Room size
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Tip: Right-sizing matters - oversized radiators can cause inefficiency and comfort issues.
Want a proper design, not a guess?
We’ll sanity-check your output and recommend the right radiator setup for comfort and efficiency.
- Right-sizing: avoid oversizing, improve control and efficiency.
- Comfort: quicker warm-up, fewer cold spots, better balance.
- System checks: pipework, radiator outputs, controls and zoning.
- Future-proofing: allowance for extensions or layout changes.
Good to know: we’ll include your calculator summary so our engineer already has the basics.
