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Chiller Tonnage Calculator

Work out chiller tonnage instantly with clear inputs, formula shown and shareable results.

About Chiller Tonnage Calculator

Water-side heat transfer is flow times temperature difference times 500, the constant that folds together water density, specific heat and minutes per hour for US gallons. Dividing by 12,000 gives tons. The classic design point of 2.4 GPM per ton corresponds to a 10 °F chilled water range.

Formulas

Water side duty

BTU/h = GPM x ΔT x 500

Tonnage

tons = BTU/h x (1 + margin) / 12000; kW = tons x 3.517

Worked example

With the default values below, Chiller Tonnage Calculator returns Chiller capacity required of 220.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Chilled water flowminimum 1 GPM
480 GPM
Water temperature differenceminimum 0.5 °F
10 °F
Sizing marginaccepts 0–40 %
10 %

Results

Chiller capacity required
220.00 tons
Duty in BTU/h
2,640,000 BTU/h
Duty in kilowatts
773.71 kW
Flow per ton
2.18 GPM/ton

Step by step

  1. 1Values used
  2. 2Water side duty
  3. 3Tonnage
  4. 4Chiller capacity required= 220.00 tons
  5. 5Duty in BTU/h= 2,640,000 BTU/h
  6. 6Duty in kilowatts= 773.71 kW
  7. 7Flow per ton= 2.18 GPM/ton

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Chiller Tonnage figure worked out?

BTU/h = GPM x ΔT x 500. Water-side heat transfer is flow times temperature difference times 500, the constant that folds together water density, specific heat and minutes per hour for US gallons.

Why increase the design ΔT?

A wider range moves the same duty with less water, cutting pump power sharply because pump power varies with the cube of flow.

What values do I need to enter?

This calculator takes 3 inputs: Chilled water flow, Water temperature difference, Sizing margin. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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