Coolant Mix Ratio Calculator
Calculate how much coolant to drain and add to achieve your desired antifreeze-to-water ratio.
Enter system capacity, current ratio, and target ratio.
Coolant Mix Instructions
Coolant mix ratio determines the freeze protection and boil-over protection of your cooling system.
Imperial formula:
Current Antifreeze = System Capacity (qts) x Current Ratio
Target Antifreeze = System Capacity (qts) x Target Ratio
Difference = Target Antifreeze - Current Antifreeze
If you need more antifreeze: drain water and add concentrate. If you need less antifreeze: drain mixture and add water.
Metric formula: Same logic using liters instead of quarts.
Common mix ratios and protection levels:
- 50/50 (antifreeze/water): -34°F / -37°C (most common)
- 60/40: -62°F / -52°C (cold climates)
- 70/30: -84°F / -64°C (extreme cold, max recommended)
Important notes:
- Never exceed 70% antifreeze — it actually reduces heat transfer
- Never go below 30% antifreeze — insufficient corrosion protection
- Most manufacturers recommend 50/50 mix
- Always use the same type of coolant (do not mix green/orange/pink)