Glycol Concentration Calculator

Calculate required glycol concentration, volume to add, specific gravity, and viscosity correction.

Propylene glycol (PG) is food-safe. Ethylene glycol (EG) has better heat transfer but is toxic.
Lowest temperature the system must withstand without freezing. Add 10F safety margin.
deg F
Total fluid volume in the system including piping, coils, and reservoir.
gallons
Current glycol percentage in the system. 0 if pure water. Test with a refractometer.
%

Results

Required Concentration:
Glycol percentage by volume needed for the target freeze protection.
-% by volume
Glycol to Add:
Gallons of pure glycol concentrate to add to reach the target concentration.
-gallons
Specific Gravity:
Specific gravity of the glycol solution at operating concentration.
-
Viscosity Correction:
Multiplier for pump sizing. Glycol solutions are more viscous than water, requiring larger pumps.
-x water
Heat Transfer Derating:
Reduction in heat transfer capacity vs pure water. Upsize coils accordingly.
-%
Reference: Dow Chemical DOWFROST/DOWTHERM Engineering Guide. ASHRAE Fundamentals - Secondary Coolants.