Heating, Cooling & Ventilation calculator
Underfloor Heating Calculator
Estimate underfloor-heating output from usable heated floor area and the selected design watts per square metre.
Estimate underfloor-heating output from usable heated floor area and the selected design watts per square metre. Before calculating, confirm the measured geometry and any product specification entered into the form. Small errors in usable heated area and W/m² can become significant across a full project. Do not count permanently covered areas unless the system manufacturer allows it. Floor finish, water temperature, spacing and heat loss determine achievable output.
What you need to enter
The Underfloor Heating Calculator uses the following project information to calculate the result.
- Heated floor area
- Design output per area
- Usable heated area (%)
Calculator result
Required heating output
How the Underfloor Heating Calculator works
The Underfloor Heating Calculator estimates required heating output from this relationship: heated area × coverage × design output. Because the page is designed for underfloor heating output across the usable heated floor area, the calculation depends especially on usable heated area and W/m². Metric and imperial entries are normalised before the arithmetic so equivalent measurements produce equivalent results.
Underfloor Heating Calculator worked example
Underfloor Heating Calculator example: For 20 m² of floor with 80% available as active heated area and a design output of 100 W/m², usable heated area is 16 m² and the nominal output target is 1.6 kW. The important sense-check is usable heated area and W/m², because that can move the real requirement away from the neat theoretical result.
Important calculation assumptions
For underfloor heating output across the usable heated floor area, do not count permanently covered areas unless the system manufacturer allows it. Floor finish, water temperature, spacing and heat loss determine achievable output.
Frequently asked questions
Which real-world inputs does the Underfloor Heating Calculator rely on?
The quality of the result starts with the inputs. Enter total heated floor area, the percentage that can genuinely contain active heating and the design output per square metre. They are used here to estimate underfloor heating output across the usable heated floor area.
Why should I check usable heated area and W/m² carefully in the Underfloor Heating Calculator?
The key uncertainty in the Underfloor Heating Calculator concerns usable heated area and W/m². Do not count permanently covered areas unless the system manufacturer allows it. Floor finish, water temperature, spacing and heat loss determine achievable output.
Can I select final equipment from the Underfloor Heating Calculator result?
Use the output target to compare underfloor systems, then verify floor finish, pipe/cable spacing, flow temperatures and actual room heat loss with the system designer. That is the practical way to carry the Underfloor Heating Calculator result into the next step.