🧊 Coolant Mix Ratio Calculator

Start by selecting your vehicle type from the dropdown to see the typical cooling system capacity range for your class of vehicle. Then enter your actual system capacity in quarts, which you can find in your owner's manual or on your manufacturer's website.

Choose the coolant type that matches what your vehicle requires. Conventional green or yellow coolant is the most common and least expensive. Extended life coolants in orange, pink, or red last significantly longer. European formulas in blue or purple are designed specifically for European makes. Your owner's manual will specify which type to use.

Select your desired mix ratio. A 50/50 mix is the standard for most climates and provides protection down to about negative 34 degrees Fahrenheit. If you live in an extremely cold region, you can increase the coolant percentage to 60/40 or 70/30 for deeper freeze protection. Finally, select whether you are doing a full refill, topping off, or a complete flush and fill. The calculator will instantly show you the exact amounts of coolant and distilled water needed, along with freeze and boilover protection temperatures and estimated cost.

Coolant, also called antifreeze, is a specially formulated liquid that serves two critical purposes in your engine. It prevents the water in your cooling system from freezing in cold weather and from boiling over in hot weather. Beyond temperature protection, coolant contains additives that inhibit corrosion and prevent scale buildup inside the engine, radiator, and heater core.

Conventional coolant uses Inorganic Additive Technology (IAT) and is typically dyed green or yellow. This type provides reliable protection but the additive package depletes relatively quickly, requiring replacement every 2 years or 30,000 miles. It has been the industry standard for decades and remains the least expensive option.

Extended life coolant uses Organic Acid Technology (OAT) or Hybrid Organic Acid Technology (HOAT). These formulas, dyed orange, pink, or red, use organic acids that deplete more slowly. They can last up to 5 years or 150,000 miles before needing replacement. Most modern vehicles from domestic manufacturers use one of these extended life formulas from the factory.

European formula coolants are phosphate free and use specific additive packages designed for the materials used in European engines. These are typically dyed blue or purple and are required for many BMW, Mercedes, Volkswagen, Audi, and Volvo vehicles. Using the wrong coolant type in a European vehicle can damage the cooling system and void warranty coverage.

The water you mix with your coolant concentrate makes a significant difference in the longevity and effectiveness of your cooling system. Tap water contains dissolved minerals such as calcium, magnesium, iron, and chlorine. When these minerals are heated repeatedly in your cooling system, they form scale deposits on internal surfaces, much like the buildup you see inside a kettle or coffee maker.

Scale deposits reduce heat transfer efficiency, which means your engine runs hotter even when the coolant level and ratio are correct. Over time, mineral deposits can also clog narrow passages in the heater core, reducing cabin heat output. Chlorine in tap water can accelerate corrosion of aluminum components, which are found in most modern radiators and engine blocks.

Distilled water has been purified through a boiling and condensation process that removes virtually all dissolved minerals and contaminants. It costs roughly $1 per gallon at most grocery and hardware stores. This small investment protects your cooling system components, which can cost hundreds or thousands of dollars to repair or replace. There is no good reason to use tap water when distilled water is so inexpensive and widely available.

A coolant flush involves draining the entire cooling system, running clean water through it to remove old coolant and contaminants, and then refilling with fresh coolant mix. This is more thorough than simply topping off or draining and refilling, because the flush step removes deposits, rust particles, and degraded additive residue that would otherwise remain in the system.

You should consider a flush when your coolant has turned brown or muddy, when you see visible rust or sediment in the overflow reservoir, or when you are switching from one coolant type to another. A flush is also recommended if the vehicle has been sitting for an extended period, if you have recently repaired a head gasket or other engine component that may have introduced contaminants, or if a coolant test strip shows that the additive package is depleted.

The basic procedure is to drain the radiator and engine block, close the drain plugs, fill the system with distilled water, run the engine until the thermostat opens and the heater is blowing warm, then drain again. Repeat this process until the water runs clear. Finally, refill with the correct coolant to water mix ratio for your vehicle and climate. If you are not comfortable performing this procedure yourself, most shops charge $100 to $200 for a professional coolant flush service.