Coolant Mix Calculator
How much antifreeze to add for the protection you need.
Enter your values
ⓘ Live results
Results
- Concentrate to add
- 4 L
- Water to add
- 4 L
- Freeze protection
- -37 °C (-34 °F)
- Boil protection (15 psi cap)
- ≈129 °C / 265 °F
- Mix ratio
- 50% coolant : 50% water
Quick answer
A 50/50 glycol mix protects to about −37 °C and raises the boiling point to about 129 °C under a 15 psi cap; going above 70% concentrate actually cools worse.
Concentrate = system capacity × target %
How to use the Coolant Mix Calculator
- 1Find the total cooling system capacity in your handbook.
- 2Choose the target concentration — 50% suits most climates, 60% for hard winters.
- 3Enter the current concentration if you are topping up rather than refilling.
Worked example
Using the values the calculator loads with:
Inputs
- Cooling system capacity8 L
- Target antifreeze concentration50 %
- Current concentration in the system0 %
Results
- Concentrate to add4 L
- Water to add4 L
- Freeze protection-37 °C (-34 °F)
- Boil protection (15 psi cap)≈129 °C / 265 °F
- Mix ratio50% coolant : 50% water
Frequently asked questions
Can I use pure antifreeze?
No. Neat glycol transfers heat far worse than a mix and actually freezes at a higher temperature than a 60/40 blend.
Which water should I use?
Deionised or distilled water only. Tap water leaves scale and minerals that corrode the radiator and heater core.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.