How to Use the Underfloor Heating Pipe Calculator
Before installing radiant floor heating, knowing how much PEX pipe you'll need lets you order the right amount of material without running short mid-project or paying for excess. Pipe is laid in evenly spaced loops across the installation area, so once you know the area and the loop spacing, you can estimate the total length fairly accurately. This calculator takes your installation area, loop spacing, and a waste allowance to give you both the base pipe length and the total length to order.
The base length comes from dividing the area by the spacing converted to feet. For example, at 8-inch spacing (0.67 ft), each square foot needs roughly 1.5 feet of pipe. Tighter spacing uses more pipe per square foot, which heats the floor more evenly but raises material and labor costs.
In practice, actual pipe use runs higher than the base calculation because of manifold connections, runs along walls, and bends in the loop pattern. A waste allowance of 10-15% is standard to cover this, and rooms with more complex layouts or multiple loops should lean toward the higher end of that range.
Frequently Asked Questions
Divide the installation area by the loop spacing (in feet) to get the base pipe length. Add a waste allowance (typically 10-15%) to cover manifold connections, wall runs, and bends to get the total length to order.
Tighter spacing heats the floor more evenly but uses more pipe and raises material and labor costs. A common approach is 8-9 inch spacing in living areas and 6 inch spacing near cold spots like windows and entryways.