PEX footage, loop count, manifold size and heat source, sized to your floor.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
| Plumbing & Heating | $1,734–$2,346 |
| Connectors & Brackets | $626–$848 |
| Insulation | $530–$718 |
| Total | $2,891–$3,911 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Enter the floor area you're heating, your tube spacing and how many thermostat zones the system needs, and the Radiant Floor Heat Calculator works out the PEX tubing to buy, how many loops the layout splits into, and the manifold, pump station and heat source sized to carry them. Loop count isn't a simple area divide — each loop is capped by a maximum run length before pressure drop gets out of hand, so a bigger room or tighter spacing means more loops, not just more tubing.
Choose how the tube goes in — tied to rebar before a slab pour, snapped into aluminum plates over an existing subfloor, or stapled up between floor joists from below — and the materials list adjusts: rebar clips for a slab, transfer plates plus thin board insulation above a subfloor, or plates with faced batt insulation in the joist bay for staple-up. It also sizes a heat source from a rough BTU-per-square-foot load, though a full room-by-room heat-loss calculation should confirm it before you buy.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Measure the floor area of every room the system will heat and decide on tube spacing — tighter spacing in cold, high-glass rooms like a sunroom or bath, wider spacing elsewhere. This is what the whole materials list scales from.
Pick in-slab for new construction, above-floor plates for a retrofit under tile or engineered wood, or staple-up if you have open joist access from below and can't touch the finished floor. Each one changes the fastening and insulation materials, not just the labor.
Sketch each room's tube run so no single loop exceeds the maximum length for your pipe size, and pick a central mechanical-room location for the manifold that keeps trunk lines short. More, shorter loops balance more evenly than one long one.
Get rigid foam under a slab, board insulation above a plated subfloor, or faced batts in the joist bay below a staple-up before the tube goes in. Skipping this step sends a meaningful share of the heat the wrong direction.
Snap it into the transfer plates, staple it to the joists, or wire it to the rebar mesh, keeping each loop's actual length within a foot or two of your layout plan. Leave enough tail at both ends to reach the manifold with slack for connections.
Cap each loop and bring it up to test pressure with air or water before it's covered by flooring or buried in concrete — a leak found now is a fitting; a leak found after the pour is a jackhammer. Hold pressure for several hours and log the reading.
Once every loop holds pressure, pour the slab, lay the underlayment and finish flooring over the plates, or close up the joist bay. Keep the system pressurized during this step as an ongoing leak check.
Plumb the manifold to the heat source through the mixing valve and circulator, then bring the system up slowly and adjust each loop's balancing valve until every zone reaches temperature at roughly the same rate.
Equip the job
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Interior & Finishing
Answers
Tube usage comes from your floor area divided by tube spacing: at 12 inches on-center you'll run about 1 foot of tube per square foot of floor, at 9 inches about 1.3 feet, and at 6 inches about 2 feet, since tighter spacing means more passes across the same area. Add the runs between the mechanical room and the manifold — the supply and return trunk lines, not just what's under the floor — plus a small allowance for connections and mistakes. This calculator adds all of that and rounds up to whole tubing rolls, since you can't buy a partial one.
Loop count isn't just the total tube length divided evenly — each individual loop is capped at a maximum run, commonly around 300 feet for half-inch PEX and 200 feet for 3/8-inch, because a longer loop creates too much resistance for a residential circulator to push water through efficiently. Once you know how many loops a zone needs, the manifold has to have that many supply-and-return port pairs, plus room for a balancing or zone valve on each one. More, shorter loops beat fewer, longer ones for even heat and easier balancing.
Embedding tube in a new concrete slab gives the best heat storage and the most even output but only works during new construction or a full tear-out, and it responds slowly to setpoint changes. Aluminum plates over an existing subfloor are the common retrofit choice under tile, engineered wood or laminate, and they respond much faster. Staple-up, fastening plates and tube to the underside of the subfloor from a basement or crawlspace, avoids touching the finished floor at all but needs insulation below it to force heat up instead of down, and it's the least efficient of the three.
Radiant floors run at much lower water temperatures than baseboard or forced air, so a modulating condensing boiler, a dedicated tankless water heater plumbed for hydronic use, or an electric boiler for smaller systems can all supply it, sized to the total BTU-per-hour load across every zone it feeds. This calculator uses a rough BTU-per-square-foot rule tied to how well-insulated the space is, which is fine for planning, but a licensed contractor should run an actual heat-loss calculation before you buy, since undersizing leaves cold spots on the coldest days and oversizing wastes money and short-cycles the equipment.
Yes, for any above-floor or staple-up install — the aluminum plates clip or snap around the tube and spread its heat sideways into the finish floor instead of leaving hot and cold stripes directly over each tube run. They come in fixed lengths, typically 4 feet, so the calculator converts your total tube footage into a plate count rather than pricing them per square foot. A slab installation skips plates entirely since the concrete itself does that heat-spreading job.
Yes — most homes run radiant floor heat as a supplemental or zoned system, keeping forced air for backup, quick recovery or areas like a garage where floor tube isn't practical, and just heating the rooms it covers, such as a bathroom, kitchen or basement, off its own small heat source and thermostat. A dedicated tankless water heater or a compact electric boiler is common for exactly this kind of single-zone add-on, since it doesn't need to double as the whole house's heat source. Keep the loop's supply temperature and its own thermostat control separate from the furnace system.