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    Hydronic Loop Sizing Calculator (Radiant Heat)

    How many GPM do I need for a given BTU heating load?

    Flow is found with the standard hydronic relation GPM = BTU/hr ÷ (500 × ΔT), where ΔT is the supply-to-return temperature drop. At a 20 F design ΔT, every 10,000 BTU/hr needs about 1 GPM. This calculator uses that formula and lets you set ΔT to 10 for radiant or 20 for baseboard.

    Run the numbers for your project

    Use the Hydronic Loop Sizing Calculator (Radiant Heat) to get an exact answer for your inputs.

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    Related questions

    Estimates and general guidance only. Verify against your local code and AHJ before any installation. Gas, electrical, and refrigerant work is hazardous to untrained users.

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