Quickly calculate the ideal antifreeze-to-water ratio for your vehicle based on climate and current mix. Helps prevent freezing in winter and overheating in summer.
Maintaining the correct coolant-to-water ratio is one of those automotive tasks that sounds simple until you're staring at an open radiator in a sub-zero winter or a record-breaking summer. I built this Antifreeze Ratio Calculator because "eyeballing it" or simply topping off with 100% coolant can be just as damaging as using plain water. Most drivers don't realize that antifreeze is a balancing act: while it prevents freezing, it is actually less efficient at carrying heat than water is.
The core problem this tool solves is the "Concentration Trap." While a 50/50 mix is the standard, increasing the concentration beyond 70% antifreeze can actually cause the mixture to freeze at higher temperatures and lead to engine overheating because the thick fluid can't transfer heat effectively. This calculator helps you find the "Goldilocks zone" for your specific climate whether you’re preparing for a northern winter or a desert summer.
By factoring in Ethylene Glycol vs. Propylene Glycol and your local temperature extremes, the tool provides specific instructions on how much to drain and fill. It moves the conversation away from "it looks green/orange enough" to a precise calculation based on the actual boiling and freezing points your engine requires to stay alive.
Pro Tip: Always use distilled water for your cooling system. Tap water contains minerals like calcium and magnesium that "cook" onto the hot internal surfaces of your engine, eventually creating a layer of scale that acts like an insulator, leading to hotspots and premature water pump failure.
A 50/50 mix of antifreeze and distilled water is the standard recommendation for most climates, offering freeze protection down to -34°F and boil protection up to 265°F.
For extremely cold climates, a stronger antifreeze mix (60/40 or 70/30) may be needed. In hot areas, a slightly higher water content can improve heat transfer. This tool helps you adjust safely.
Distilled water is always recommended to avoid minerals that can corrode your cooling system. This tool assumes you’re using distilled water.
Different coolants (ethylene glycol vs. propylene glycol) have different freeze and boil points. Our calculator accounts for this so you can select the right mix.
You can use an inexpensive antifreeze tester (hydrometer or refractometer) to determine the freeze point of your existing coolant. Input that into the calculator for custom recommendations.
Yes, this tool applies to nearly all gasoline and diesel vehicles with liquid cooling systems. Always consult your vehicle manual for manufacturer-specific recommendations.