What this calculator does
The Antifreeze Mixture Calculator tells you the final coolant concentration (percent antifreeze by volume) when you combine a measured amount of antifreeze with a measured amount of water. It is useful for engine coolant, solar loops, and any glycol-based heat-transfer fluid where the mix ratio determines freeze protection and boil-over resistance.
How to use it
Enter the volume of pure (or concentrated) antifreeze and the volume of water you are adding. Use the same unit for both — litres, quarts, or gallons all work, since the result is a ratio. The calculator returns the antifreeze percentage, the matching water percentage, and the total mixture volume.
The formula explained
The concentration is simply the part divided by the whole: $$\text{final \%} = \frac{V_{\text{antifreeze}}}{V_{\text{antifreeze}} + V_{\text{water}}} \times 100$$ The denominator is the total mixture volume. Because it is a pure ratio, the units cancel and only consistency matters.
Worked example
Mix 5 litres of antifreeze with 5 litres of water. Total volume = 10 litres. Final concentration = $$\frac{5}{10} \times 100 = 50\%$$ A typical 50/50 mix gives roughly -37 C freeze protection for ethylene-glycol coolant.
FAQ
Does it matter what unit I use? No — as long as both fields use the same unit, the percentage is identical.
What about already-diluted antifreeze? This tool treats the antifreeze input as the antifreeze portion. If you start with a pre-mixed product, enter its effective antifreeze volume.
What is a common target? Many vehicles specify a 50/50 mix; check your owner manual for cold-climate ratios up to about 70/30.
