Free Mechanical / HVAC calculator

Heating and chilled-water flow calculator

Calculate mass and volume flow from thermal duty, flow/return temperatures and user-entered fluid properties.

Enter the project values

All values remain in your browser. Review the assumptions before using the result.

Your result will appear here.Calculate to see the outputs, formula and substituted working.

How the calculation works

First-principles hydronic energy balance with editable fluid properties.

Formula

ṁ = Q ÷ (cp × ΔT); V̇ = ṁ ÷ ρ

Worked example

Duty100 kW

Temperatures70°C / 60°C

cp / density4.186 kJ/kgK / 998 kg/m³

Expected volume flow2.394 L/s

Assumptions and limitations

Assumptions

Duty is transferred entirely to or from the fluid.
Fluid properties are represented by the entered values.

What this does not check

Does not select pipe size, pump, valve or plant.
Does not model glycol properties, diversity or control conditions automatically.

Formula version: 1.0 · Last reviewed: 16 August 2026

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Engineering basis: first-principles calculation using user-entered project data. The calculator does not choose design criteria or replace the complete project-specific engineering design.

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