What is a ton of refrigeration?

One ton of refrigeration (TR) equals 12,000 BTU/hr or approximately 3.517 kW. It historically represents the cooling effect of melting one short ton (2,000 lb) of ice per day.

What formula does this calculator use?

For water: Q (BTU/hr) = GPM × 500 × ΔT°F, where 500 is a constant derived from water's density (8.34 lb/gal) × 60 min/hr × Cp (≈1 BTU/lb·°F). Dividing by 12,000 gives tons.

What is a typical chilled water temperature differential?

Most chilled water systems use a 10–14°F (5.6–7.8°C) differential. A common design point is 44°F supply and 54°F return (10°F ΔT). Larger ΔT improves efficiency and reduces pump energy.

Why does my calculated tonnage differ from the nameplate rating?

Nameplate ratings are at ARI/AHRI standard conditions (44°F supply, 85°F condenser entering). Real-world conditions, fouling, and part-load operation shift actual capacity. Always add a safety factor of 10–15% to the calculated load.

Can I use this for glycol systems?

You can enter the solution-specific heat (Cp), but this simplified calculator assumes water density. For a precise glycol result, use a method that also accepts solution density.

Chiller Tonnage Calculator

Calculate chiller capacity in tons of refrigeration from water flow rate and supply/return temperature difference.

Chiller Inputs

Unit System

Chilled Water Flow Rate (GPM)

Return Water Temperature (entering chiller) (°F)

Supply Water Temperature (leaving chiller) (°F)

Specific Heat of Fluid (Cp) (BTU/lb·°F)

Water = 1.00. 30% ethylene glycol ≈ 0.89.

Enter flow rate and temperatures, then click Calculate.

Summary

This calculator determines the cooling capacity required for a chilled water system using the standard heat transfer equation Q = m × Cp × ΔT. Enter the chilled water flow rate and the supply/return temperature differential to get the required chiller size in tons of refrigeration (TR), kilowatts (kW), and BTU per hour.

How it works

Enter the chilled water flow rate in gallons per minute (GPM) or liters per second (L/s).
Input the chilled water return temperature (entering the chiller).
Input the chilled water supply temperature (leaving the chiller).
The calculator applies Q = Flow × Cp × ΔT to compute the cooling load.
Results are shown in tons of refrigeration (TR), kilowatts (kW), and BTU/hr.

Use cases

Size a new chiller plant for a commercial building.
Verify existing chiller capacity against actual load.
Cross-check HVAC design drawings against measured flow and temperatures.
Audit chiller efficiency during commissioning or energy retrofits.
Estimate cooling needs for data center chilled water systems.
Convert between tons of refrigeration, kW, and BTU/hr for specs.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu