Coolant Mix Calculator

The Coolant Mix Calculator tells you exactly how much coolant to drain and replace to hit your target antifreeze concentration — protecting your engine from freezing or overheating. Enter your current system volume, current concentration, and desired concentration, then select your minimum expected temperature to get the volume to drain, how much pure coolant and water to add back, plus your resulting freeze protection and boil point.

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Total volume of your cooling system

%

Current antifreeze concentration in your system

%

Target antifreeze concentration for your climate

Lowest temperature expected in your area

Results

Volume to Drain

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Add Pure Coolant

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Add Water

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Freeze Protection

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Boil Point

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Frequently Asked Questions

What is the ideal coolant concentration for most climates?

A 50/50 mix (50% coolant, 50% water) is recommended for most climates as it provides freeze protection to about -34°F (-37°C) and optimal heat transfer properties.

How do I test my current antifreeze mixture?

Use a coolant tester, refractometer, or hydrometer to measure the specific gravity or freezing point of your coolant mixture. These tools give accurate readings of your current concentration.

Can I use more than 70% coolant concentration?

No, using more than 70% coolant actually reduces freeze protection and heat transfer efficiency. Pure coolant freezes at a higher temperature than a proper mix.

What's the difference between automotive and CNC coolant?

Automotive coolants contain additives for rubber seals and metal protection, while CNC coolants are designed for machining operations with different viscosity and lubrication properties.

How often should I check my coolant mixture?

Check your coolant concentration at least twice a year, before summer and winter seasons, or whenever you add coolant to the system.

What type of water should I use for mixing coolant?

Use distilled or deionized water when mixing coolant. Tap water contains minerals that can cause scaling and reduce the effectiveness of the coolant system.

Why is proper coolant mixture important?

The correct mixture prevents freezing in winter, raises the boiling point in summer, prevents corrosion, and ensures optimal heat transfer from your engine.