How much underfloor heating pipe do I need?

Getting the pipe quantity right saves money twice. Buy too little and you have a joint in the floor or a second delivery. Buy too much and you pay for a coil you never open. This guide gives you the figures, the loop limits and three worked examples using real MaxHeatUFH coil sizes and prices.

The method is the same for screed, overlay boards, castellated panels and joisted floors. Only the pipe size and the spacing change.

How much pipe do I need per m²?

Pipe per m² is 1,000 divided by your pipe centres in mm. At 150mm centres that is 1,000 ÷ 150 = 6.7m of pipe for every square metre of heated floor.

These are the full-coverage figures. Maker installation guides often quote a little less, for example 9m/m² at 100mm and 4.5m/m² at 200mm, because the pipe stops short of the walls. Using the full figure gives you a small safety margin.

Measure only the floor you will heat. Leave out the footprint of kitchen units, islands, baths, shower trays, WCs, fitted wardrobes and stairs. Pipe under fixed units is wasted and can overheat what sits on it.

Which pipe centres should I use?

Use 150mm as the default for most rooms, 100mm where you need more output and 200mm in well-insulated rooms with low heat loss. Closer centres put more pipe in the floor, so the floor gives out more heat at the same water temperature.

• 100mm: rooms with high heat loss, large glazing, floor coverings with a higher tog, or heat pump systems running at low flow temperatures.
• 150mm: most living rooms, kitchens and bedrooms on a gas boiler or a well-designed heat pump system.
• 200mm: well-insulated new builds and rooms with low heat demand.

Spacing changes pipe quantity a lot. A 30m² room needs 300m at 100mm centres but 150m at 200mm. Our guide to pipe centres: 100, 150 or 200mm covers the choice in detail.

How long can one underfloor heating loop be?

Keep each 16mm loop to 100m or less and each 12mm loop to 80m or less, including the tails to and from the manifold. These are the limits used in maker installation guides for screeded floors (100m) and 12mm overlay systems (80m).

Longer loops need more pump pressure to push water round and lose more heat along the way, so the far end of the loop runs cooler. Short loops are fine, but keep loops on the same manifold as close in length as you can so they balance easily.

A 100m loop at 150mm centres covers about 15m² with no tails. Real loops have tails, so plan on 12 to 14m² per 16mm loop at 150mm, and about 10 to 12m² per 12mm loop at 150mm.

How do I work out the pipe for a room, step by step?

1. Measure the heated area. Room area minus fixed units and sanitaryware, in m².
2. Work out floor pipe. Heated area × pipe per m² for your centres.
3. Measure the tails. Distance from the room to the manifold, then double it (flow and return). Every loop has its own pair of tails.
4. Count the loops. Divide floor pipe plus tails by the loop limit (100m for 16mm, 80m for 12mm) and round up.
5. Set the loop length. Split the floor pipe evenly between the loops and add each loop's tails.
6. Add 10%. Add 10% to each loop, plus about 1m for the manifold connections, so the last loop on a coil never runs short.
7. Choose coils. Fit whole loops onto whole coils. Never join a loop mid-floor to use up an offcut.

Worked example: one 20m² kitchen extension

A 20m² heated area at 150mm centres in 16mm pipe, with the manifold 4m away, needs two loops of about 75m and one 200m coil.

1. Floor pipe: 20 × 6.7 = 134m.
2. One loop would be 134m + 8m tails = 142m. That is over 100m, so use two loops.
3. Each loop: 67m in the floor + 8m tails = 75m.
4. With 10% and 1m for connections, each loop needs about 83m of coil.
5. Two 80m coils are too short, so both loops come off one 200m coil.

On 16mm PERT-AL-PERT the 200m coil is £143. On 3-layer 16mm PERT-EVOH the 200m coil is £118 (inc VAT, October 2026). This room needs a 2 port manifold.

Worked example: a whole ground floor

A 72m² heated ground floor at 150mm centres in 16mm pipe needs 8 loops and about 570m of pipe, which fits on two coils.

Tails in this example are 2m (hall) to 8m (lounge) each way. The total is 566m of loop. With 10% and connections added, the eight loops need about 631m of coil.

• PERT-EVOH 16mm: one 400m coil for the three kitchen loops and one lounge loop (about 391m), and one 240m coil for the other lounge loop, the hall, utility and WC (about 239m). Total 640m for £379.
• PERT-AL-PERT 16mm: one 500m coil and one 150m coil. Total 650m for £464.

Prices are inc VAT, October 2026. Buying one 500m coil instead of six 100m coils also means fewer offcuts to throw away. A pipe decoiler makes long coils much easier to lay without kinks.

This floor needs an 8 port manifold. Our guide to how many manifold ports you need covers what goes with it.

Which coil sizes can I buy?

MaxHeatUFH sells UFH pipe in whole coils only. Choose the combination that gives the least pipe overall, then the fewest coils.

Prices inc VAT, October 2026. 16mm PERT-AL-PERT comes in 50, 80, 100, 150, 200, 300 and 500m coils. 16mm 3-layer PERT-EVOH comes in 100, 200, 240, 400 and 500m coils.

Use 12mm pipe for overlay and low-profile panels and 16mm for screed, castellated panels and routed boards. For the differences between the pipe types, see UFH pipe types compared.

What else do I need to allow for?

Tails are the part people forget. A loop that serves a bedroom 10m from the manifold uses 20m of its 100m just getting there and back, which leaves 80m for the room.

• Put the manifold central. Short tails mean more of each loop heats the room it is meant for.
• Sleeve tails through busy areas. Where many tails pass through a hall or cupboard, use pipe conduit to stop that floor running too warm.
• Allow for fixings. Clipped screed systems need pipe clips or clip rail. Panel systems hold the pipe in the board.
• Allow two Eurocone connector cores per loop sized to your pipe, for example 16 × 2.0.

Products for this job

• PERT-AL-PERT Multilayer UFH Pipe
• 3-Layer PERT-EVOH Oxygen Barrier UFH Pipe
• 5-Layer PERT-EVOH UFH Pipe 16mm
• Pipe Decoiler
• High Grip Barbed Pipe Clips
• Eurocone Connector Cores 3/4"
• All UFH pipe

Related guides: How many manifold ports do I need?, Pipe centres: 100, 150 or 200mm? and How to install water underfloor heating.

Frequently asked questions

How many metres of underfloor heating pipe per m²?

10m per m² at 100mm centres, 6.7m at 150mm and 5m at 200mm. Add the tails back to the manifold on top.

How many m² does a 100m coil of UFH pipe cover?

About 15m² at 150mm centres if there were no tails. In practice, with tails to the manifold, plan on 12 to 14m² per 100m loop.

Can I join underfloor heating pipe to make a loop longer?

Avoid it. Each loop should be one continuous length from manifold flow to manifold return. Plan your coils so no loop needs a joint in the floor.

Do the pipes back to the manifold count towards the loop length?

Yes. The 100m limit for 16mm pipe and 80m limit for 12mm pipe include the flow and return tails.

Should I buy one big coil or several small ones?

Buy the combination with the least total pipe. Several loops can share one coil, and one long coil often leaves less waste than many short ones.

How much extra pipe should I order?

Add 10% to each loop plus about 1m for the manifold connections. This covers bends, small measuring errors and trimming at the manifold.

Do I need 12mm or 16mm pipe?

12mm suits overlay and low-profile boards where height is tight. 16mm suits screed, castellated panels and routed boards, and allows longer loops.

Sources: Polypipe solid floor UFH installation guide, Polypipe UFH existing floors installation guide