GPM to Tons Calculator – Convert Chiller Capacity (Free Tool)

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GPM to Tons Calculator: Convert Water Flow to Cooling Capacity (Free Tool)

You are designing a chilled water system. You know the flow rate is 100 GPM. The temperature drop across the chiller is 10°F. How many tons of cooling capacity does that represent?

In the HVAC industry, tons and GPM are closely linked. The relationship between water flow, temperature difference, and cooling capacity is fundamental to chiller design and troubleshooting.

Today, I give you a free GPM to Tons Calculator.

You enter the flow rate (GPM) and temperature difference (ΔT). The calculator shows the cooling capacity in tons.

The calculator uses the standard HVAC formula: Tons = (GPM × ΔT) ÷ 24.

Let me explain how GPM relates to cooling tons and how to use this calculator.

What is the Relationship Between GPM and Tons? (Simple Explanation)

In chilled water systems, the cooling capacity of a chiller is determined by the water flow rate and the temperature difference across the evaporator.

The formula:

Tons = (GPM × ΔT) ÷ 24

Where:

  • GPM = gallons per minute of chilled water flow
  • ΔT = temperature difference between entering and leaving water (°F)
  • 24 = a constant derived from water properties (8.33 lb/gal × 60 min/hr ÷ 12,000 BTU/ton)

Example: A chiller with 240 GPM and a 10°F ΔT produces 100 tons of cooling.

Why This GPM to Tons Calculator Matters

Here is why you need to calculate cooling capacity from flow and temperature.

Reason 1: Verify chiller performance

Measuring actual GPM and ΔT lets you calculate the actual tonnage a chiller is delivering. This is essential for commissioning and troubleshooting.

Reason 2: System design

Designers use this relationship to size chillers, pumps, and piping. A 500-ton chiller at 44°F supply and 56°F return requires 1,000 GPM.

Reason 3: Diagnose problems

If a chiller is not delivering its rated capacity, low ΔT or low flow could be the cause. Reduced ΔT at full flow means the chiller is only partially loaded.

Reason 4: Evaluate system efficiency

The relationship helps you understand the impact of flow changes. Increasing GPM can compensate for reduced ΔT, but at a cost in pump energy.

Reason 5: Estimate energy use

Cooling capacity in tons translates directly to energy consumption. 1 ton = 3.517 kW of cooling effect.

LIVE GPM to Tons Calculator

Enter flow rate and temperature difference. The calculator shows cooling capacity instantly.

❄️ GPM to Tons Calculator

Convert water flow and temperature difference to cooling capacity

💧 Flow Rate (GPM)

🌡️ Temperature Difference (ΔT °F)

📏 Application

❄️ COOLING CAPACITY
0.0 Tons
0%
📊 BTU/hr: 0 ⚡ kW: 0.0
💡 Formula: Tons = (GPM × ΔT) ÷ 24 for evaporators[citation:6]. Divide by 30 for condensers[citation:6].
📐 1 ton = 12,000 BTU/hr. For water: 500 × GPM × ΔT = BTU/hr[citation:3].

❄️ GPM to Tons Calculator

Convert water flow and temperature difference to cooling capacity

💧 Flow Rate (GPM)

🌡️ Temperature Difference (ΔT °F)

📏 Application

Chiller Evaporator (Tons = GPM × ΔT ÷ 24) Chiller Condenser (Tons = GPM × ΔT ÷ 30)

❄️ COOLING CAPACITY

0.0 Tons

0%

📊 BTU/hr: 0⚡ kW: 0.0

💡 Formula: Tons = (GPM × ΔT) ÷ 24 for evaporators. Divide by 30 for condensers.

📐 1 ton = 12,000 BTU/hr. For water: 500 × GPM × ΔT = BTU/hr.

How to Use This GPM to Tons Calculator

Follow these 3 simple steps.

Step 1: Enter the water flow rate in gallons per minute (GPM)
Step 2: Enter the temperature difference (ΔT) in °F between entering and leaving water
Step 3: Select the application (chiller evaporator or condenser)

The calculator shows:

  • Cooling capacity in tons
  • BTU/hr
  • Cooling power in kW

The Formulas Explained

Chiller Evaporator (Cooling Capacity):

Tons = (GPM × ΔT) ÷ 24

This formula applies to the chilled water side of the chiller where water is cooled.

Chiller Condenser (Heat Rejection):

Tons = (GPM × ΔT) ÷ 30

This formula applies to the condenser water side where heat is rejected. The divisor is larger because condenser water has a different temperature range and specific heat.

Real Examples

Example 1: Chiller Evaporator

  • Flow: 240 GPM
  • ΔT: 10°F (54°F entering, 44°F leaving)
  • Tons = (240 × 10) ÷ 24 = 100 tons

Example 2: Chiller Condenser

  • Flow: 180 GPM
  • ΔT: 5°F (50°F entering, 55°F leaving)
  • Tons = (180 × 5) ÷ 30 = 30 tons

Example 3: Small System

  • Flow: 40 GPM
  • ΔT: 12°F
  • Tons = (40 × 12) ÷ 24 = 20 tons

Typical GPM per Ton

For chilled water systems:

  • 2.0 GPM per ton at 12°F ΔT
  • 2.4 GPM per ton at 10°F ΔT
  • 3.0 GPM per ton at 8°F ΔT

Formula: GPM/ton = 24 ÷ ΔT

Frequently Asked Questions (FAQs)

1. What is the formula for cooling tons from GPM?

Tons = (GPM × ΔT) ÷ 24 for evaporators.

2. What is the formula for condenser tons from GPM?

Tons = (GPM × ΔT) ÷ 30 for condensers.

3. What is a typical ΔT for a chiller?

10-12°F for standard chilled water systems. 8-15°F range is common.

4. What is the constant 24 in the formula?

It comes from: 8.33 lb/gal × 60 min/hr ÷ 12,000 BTU/ton ≈ 24.

5. How many GPM does a 100-ton chiller need?

At 10°F ΔT: 100 × 24 ÷ 10 = 240 GPM.

6. How do I measure ΔT?

Measure the entering and leaving water temperatures at the chiller.

Final Thoughts

The relationship between GPM, ΔT, and tons is fundamental to HVAC system design.

My GPM to Tons Calculator gives you:

  • Instant cooling capacity from flow and temperature
  • Evaporator and condenser formulas
  • BTU/hr and kW equivalents

Bookmark this page. Use it for chiller design, commissioning, and troubleshooting.

The next time you need to know how many tons a chiller is delivering, you will have the answer.

Disclaimer: This is an educational tool based on standard HVAC formulas. For glycol systems, adjust for specific heat and specific gravity.

External Links (Authority Backlinks):

  1. Wikipedia – Ton of refrigeration{:target=”_blank” rel=”noopener noreferrer”}
  2. Wikipedia – Gallon per minute{:target=”_blank” rel=”noopener noreferrer”}
  3. Wikipedia – Chiller{:target=”_blank” rel=”noopener noreferrer”}
  4. Wikipedia – HVAC{:target=”_blank” rel=”noopener noreferrer”}

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