Underfloor Heating Pipe Spacing Calculator

Underfloor heating is sold by the metre of pipe and the millimetres between runs - both set by how much heat the floor must give up. Get the spacing wrong and the room either loafs or lays tile over a lukewarm slab.

Underfloor Heating Pipe Spacing Calculator turns floor area, heat demand, construction and water temperature into a recommended spacing, pipe length and circuit count.

• Heat demand: Per-square-metre requirement.
• Pipe options: 16 mm and 20 mm.
• Floor types: Screed, timber, plates.
• Water temp: Flow temperature model.
• Circuits: Pipe length and manifold split.
• Export: Text, CSV or JSON report.

1. Enter floor area and heat demand.
2. Pick pipe size, construction and flow temperature.
3. Read the recommended spacing and output.
4. Check pipe length and number of circuits.
5. Export the result if needed.

Example 1. A 20 m2 living floor needing 75 W/m2 in a screed at 200 mm spacing and 45 C flow delivers about the required output - roughly 100 m of 16 mm pipe, a single circuit.

Example 2. The same floor on timber at 200 mm delivers much less - restore output by tightening to 150 mm or lifting the flow temperature, otherwise a supplementary radiator is needed.

• Layout ready: Spacing and length up front.
• Construction aware: Floor type modelled.
• Circuit planning: Manifold split estimated.
• Honest limits: Warns when the floor cannot cope.
• Free and private: No uploads, no logging.