What pipe spacing should I use for underfloor heating?

Standard domestic installations use 150mm centres, which provides a good balance of heat output and pipe usage. Use 100mm centres for rooms with high heat loss (conservatories, rooms with lots of glazing) or when using a heat pump with lower flow temperatures. Use 200mm centres for well-insulated rooms or supplementary heating.

What is the maximum loop length for underfloor heating?

For 16mm pipe (the most common domestic size), the maximum recommended loop length is 80m per circuit. For 20mm pipe, it is approximately 120m. Exceeding these lengths causes excessive pressure drop and uneven heating. Larger rooms should be split into multiple circuits connected to a manifold.

Do I need a manifold for underfloor heating?

Yes. Every wet underfloor heating system needs a manifold to distribute water to each circuit (loop) and control the flow temperature. Even a single room needs a manifold if it has multiple circuits. Manifolds are typically sized by the number of circuits — common sizes are 2-port to 12-port.

Can I use underfloor heating with a combi boiler?

Yes, but you will need a blending valve (thermostatic mixing valve) to reduce the boiler flow temperature from ~70°C to the 35-50°C required for underfloor heating. Alternatively, many modern combi boilers have a low-temperature mode specifically for UFH. Underfloor heating works best with heat pumps which naturally operate at lower temperatures — see our Heat Pump Sizing Calculator and Boiler Size Calculator for help choosing.

How much does underfloor heating pipe cost?

PEX or PE-RT underfloor heating pipe typically costs £0.50-£1.50 per metre in the UK, depending on brand and quantity. A 100m coil of 16mm pipe costs roughly £50-£120. Budget quality pipe is at the lower end; premium brands like Rehau, Polypipe, or JG Speedfit are at the higher end. Use our optional price input for a cost estimate.

Underfloor Heating Pipe Calculator — How Much UFH Pipe Do I Need?

Underfloor Heating Pipe Calculator — How Much Pipe Do I Need?

Calculate the total pipe length and number of coils for your underfloor heating installation. UK standard pipe spacings and sizes.

Room Length

Room Width

Pipe Spacing

Pipe Diameter

Coil Length

Standard coil size you plan to buy

Manifold Distance

Distance from manifold to room (one way)

Include wastage allowance

Adds 5% extra for cutting waste and layout variations

Wastage Percentage

5% recommended for professionals, 10% for DIY or complex layouts

Price Per Coil (optional)

Enter your supplier price for a cost estimate

How We Calculate This

Our underfloor heating pipe calculator determines the total pipe length based on your floor area and chosen pipe spacing, then calculates how many standard coils you need to order.

The formula

Pipe length = (Floor area ÷ Pipe spacing) + Manifold allowance

For example, a 20 m² room at 150mm spacing needs: 20 ÷ 0.15 = 133m of pipe, plus approximately 8m for manifold connections (4m each way for flow and return), giving ~141m total. With 5% wastage: ~148m. You would need 2 x 100m coils.

Circuit planning

We check whether the total pipe length exceeds the recommended maximum loop length for your pipe diameter. If it does, we advise splitting into multiple circuits, each connected to the manifold independently. This ensures even heat distribution and avoids excessive pressure drop, in line with BS EN 1264 (Water based surface embedded heating and cooling systems).

Standard coil sizes

50m coil: Small rooms and top-ups
100m coil: Most popular domestic size
120m coil: Common mid-size option
150m coil: Larger installations

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Underfloor Heating Pipe Calculator — How Much Pipe Do I Need?

How We Calculate This

The formula

Circuit planning

Standard coil sizes

Frequently Asked Questions

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