Calculate HVAC subcooling from saturated liquid and liquid line temperatures, or estimate it from refrigerant, high-side pressure, and line temperature.

Subcooling Calculator

Temperature input
Pressure input

Enter any 2 values to calculate the missing variable.

Subcooling Formula

The following formula is used to calculate a subcooling temperature. 

SCT = SLT - LLT
  • Where SCT is the subcooling temperature
  • SLT is the saturated liquid temperature
  • LLT is the liquid line temperature

To calculate the subcooling temperature, subtract the liquid line temperature from the saturated liquid temperature.

For the formula above, the units of the temperature of both the saturated temperature and the liquid line temperature should match to ensure a correct calculation.

Subcooling Definition

What is subcooling?

Subcooling is a term used in chemistry to describe the state of a liquid in which it is existing at a temperature below its normal boiling point. In most cases, this would be standard pressure.

This term is most often used in the analysis of the refrigeration cycle. Subcooling is important to determine how well a refrigeration system is operating.

Example Problem

How to calculate subcooling temperature?

  1. First, determine the saturated liquid temperature.

    For this example problem, the saturated liquid temperature is 121 F.

  2. Next, determine the liquid line temperature.

    In this example, the liquid line temperature is measured to be 104 F.

  3. Finally, calculate the subcooling temperature of the refrigeration device.

    Using the formula above, the subcooling temperature to calculated to be:
    SCT = SLT - LLT
    SCT = 121F - 104F
    SCT = 17F