Radiant floor heating calculators online tend to come from a single manufacturer or supplier and cover just one slice of the decision — a PEX-length tool, a BTU worksheet, or a cost estimator, each tuned to sell that vendor's kit. This calculator walks the whole path instead: how much heat a room needs, how much tubing or electric mat that translates into, and what it costs to run either system, so you can compare electric and hydronic on equal footing before you buy anything.

How the Radiant Floor Heating Calculator works

The calculator starts with a BTU-per-square-foot heat-output target based on your room type, climate zone, and insulation quality — typically in the 20-50 BTU/sq-ft range used in radiant design guides. That target multiplied by your floor area gives the total design heat load in BTU per hour.

For an electric mat, wattage follows a standard ~12 W/sq-ft rating for thin electric radiant mats; multiplying by a typical daily runtime and your electricity price gives the monthly cost. For hydronic PEX, tubing length follows the standard serpentine rule (area × 12/spacing), split into loops that stay under the maximum length for the pipe size in use (250-400 ft depending on 3/8", 1/2", or 5/8" PEX), and the running cost converts the heat load into gas therms at a typical 85% boiler efficiency.

Inputs and what they mean

Floor area and room type set the baseline heat need — bathrooms and garages typically need more BTU/sq-ft than a well-insulated living room. Climate zone and insulation quality adjust that baseline up or down; a poorly insulated room in a cold climate can need well over twice the heat output of a well-insulated room in a warm one.

System type (electric vs hydronic) and, for hydronic, tube spacing determine how the heat is delivered and how much material the install needs. Electricity and gas prices are the biggest lever on running cost — pull your actual per-unit rate from a recent utility bill rather than a national average for the most accurate comparison.

Limits and edge cases

This calculator uses rule-of-thumb design values, not a room-by-room heat-loss calculation from a Manual J load study. Actual heat loss depends on window area, ceiling height, air sealing, and exterior wall exposure in ways a single BTU/sq-ft number can't fully capture. Install costs are rough per-square-foot estimates and will vary widely by region, contractor, and whether an existing boiler or electrical circuit needs upgrading.

For anything beyond a single small room — and especially for whole-home hydronic systems — get a design from a licensed HVAC contractor who can run a proper heat-loss calculation and size the boiler, manifold, and zoning correctly before you buy tubing or mats.