How Much Underfloor Heating Pipe Do I Need?
Quick Answer
Approximately 100–120m of pipe for a 20m² room
Based on: 20m² floor area, 200mm pipe centres, 16mm PEX or PE-RT pipe
How We Calculated This
- Floor area: 20m²
- Pipe centres: 200mm (standard for well-insulated rooms)
- Pipe per m²: 1000 ÷ 200 = 5m/m²
- Sub-total: 20 × 5 = 100m
- Plus flow/return runs to manifold: ~10–20m
- Total: 110–120m
Pipe Spacing by Application
- 100mm centres: High heat output areas (conservatories, poorly insulated rooms) — 10m/m²
- 150mm centres: Standard rooms with moderate heat loss — 6.7m/m²
- 200mm centres: Well-insulated rooms (most common) — 5m/m²
- 250mm centres: Low heat demand areas — 4m/m²
Maximum Loop Lengths
Each circuit (loop) should not exceed the maximum length to maintain even heat distribution:
- 12mm pipe: 60m max loop
- 16mm pipe: 100m max loop
- 20mm pipe: 120m max loop
If the total pipe needed exceeds the max loop length, split into multiple circuits connected to a manifold.
Pipe Types
- PE-RT: Most common, flexible, cost-effective
- PEX-A: Cross-linked, shape memory, premium choice
- Multilayer (MLCP): Aluminium core, holds shape, easier to install
Last updated: April 2026