Radiant Floor Heating Calculator

Background.

A reader arrives at Radiant Floor Heating Calculator to convert a professional area load into delivered heat and gross up for system efficiency. Radiant floor output starts with a room-by-room heat loss in Btu per hour per square foot, not a universal wattage allowance. For that reason, this page names its convention as “delivered load = floor area × professional Btu/h·ft² load; required input = delivered load ÷ system efficiency.”

The editable entries are heated floor area, professional design heat load, delivered-system efficiency. Use values from the document or measurement that governs this radiant floor heating question; the defaults are only the worked fixture below. Before relying on the number, check this radiant floor heating boundary: floor covering, water temperature, tube spacing, downward loss, controls and floor output limits require design.

ASHRAE Handbook—Fundamentals, duct design and heat-transfer methods (PAYWALL) documents the convention or governing rule used here. The radiant floor heating output is a transparent scenario under those facts: it does not manufacture an unentered market price, professional determination, carrier quote, legal eligibility finding or locally adopted code value.

What is radiant floor heating calculator?

Radiant Floor Heating is the relationship behind this decision: radiant floor output starts with a room-by-room heat loss in Btu per hour per square foot, not a universal wattage allowance. On this page it means delivered load = floor area × professional Btu/h·ft² load; required input = delivered load ÷ system efficiency. Floor covering, water temperature, tube spacing, downward loss, controls and floor output limits require design; that is the line between the reported quantity and a broader hvac analysis.

How to use this calculator.

1. 01Confirm that “delivered load = floor area × professional Btu/h·ft² load; required input = delivered load ÷ system efficiency” matches the radiant floor heating convention you need.
2. 02Replace the fixture values for heated floor area, professional design heat load, delivered-system efficiency with dated values from the governing record.
3. 03Keep all currencies, measurement units and time periods on the same basis before calculating.
4. 04Read required heat-source input together with this boundary: Floor covering, water temperature, tube spacing, downward loss, controls and floor output limits require design.

The formula.

The calculation uses delivered load = floor area × professional Btu/h·ft² load; required input = delivered load ÷ system efficiency. In this radiant floor heating model, the entered terms are heated floor area, professional design heat load, delivered-system efficiency. Radiant floor output starts with a room-by-room heat loss in Btu per hour per square foot, not a universal wattage allowance, which is why the relationship is presented under this name rather than as a universal alternative. Floor covering, water temperature, tube spacing, downward loss, controls and floor output limits require design. Calculations keep full decimal precision through the relationship and round only the returned display values.

A worked example.

Frequently asked questions.

References& sources.

1. [1]ASHRAE Handbook—Fundamentals, duct design and heat-transfer methods (PAYWALL). Retrieved 2026-08-07. access: open unless marked otherwise.
2. [2]Air Conditioning Contractors of America. Manual J — residential load calculation. Retrieved 2026-08-07. independence: primary; access: open.
3. [3]International Code Council. 2024 International Energy Conservation Code (IECC). Retrieved 2026-08-07. independence: primary; access: open.