Underfloor Heating
Underfloor Heating Pipe Length Calculator
Pipe metres and loops for a floor area
Updated 12 July 2026 · Live
What this tool does
Works out the total underfloor heating pipe length and the number of loops from the floor area and the pipe spacing.
Enter the floor area, pipe spacing and maximum loop length; the calculator returns the total pipe length and loops.
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Formula Used
Works out the total underfloor heating pipe length and the number of loops from the floor area and the pipe spacing. It runs entirely in your browser and shows the working, so you can check every step against your own figures.
How the underfloor heating pipe length calculator works
At a given spacing the pipe run per square metre is one divided by the spacing in metres, so the total run is the floor area divided by the spacing, plus about 10% for the bends and the tails back to the manifold. Dividing that by the maximum loop length and rounding up gives the number of loops the floor needs.
What you enter
Enter the floor area, pipe spacing and maximum loop length; the calculator returns the total pipe length and loops. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
The pipe metres set your material order; the loop count feeds straight into the manifold-port tool. Keep loops under the maximum length so each one balances and flows without a big pump.
Safe by design
This tool sizes pipe, manifold, coverage and cost. It never sets flow temperatures or heat-source settings — commissioning the system is a qualified heating engineer’s job.
Assumptions and limits
This is a whole-floor estimate at one spacing. In practice you tighten the spacing to 100 mm at cold perimeters and open it out elsewhere, and each room usually gets its own loop. A detailed design allocates loops room by room.
Using it with the rest of BuildMetricLab
This calculator is one step in planning the job. Pair it with the related tools in this category and across BuildMetricLab to go from a single figure to a full costed plan — a sizing figure feeds a cost estimate, a cost estimate feeds a project budget, and each result carries straight into the next tool. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Works out the total underfloor heating pipe length and the number of loops from the floor area and the pipe spacing. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or rates are embedded.
Frequently asked questions
What pipe spacing should I use?
150–200 mm is common; tighten to 100 mm at cold edges like external walls and under glazing for even warmth.
Why limit loop length?
Long loops have high resistance and uneven temperature end to end. Keeping each under about 100 m lets them balance and flow easily.
Does each room need its own loop?
Usually yes, so each room can be controlled separately. The loop count here is a total; a full design splits it by room.
Why add 10%?
The extra covers the bends in the serpentine pattern and the tails running back to the manifold, which the bare area-÷-spacing figure misses.
Spotted something off?
Calculations or display — let us know.