Coolant Mix Ratio Calculator
Quick answer: A 12-quart cooling system at 50/50 needs 6 quarts of concentrated antifreeze and 6 quarts of distilled water.
This coolant mix ratio calculator tells you exactly how much concentrated antifreeze and distilled water to add for any system capacity and target concentration. Enter your cooling system capacity and the antifreeze percentage you want — results update instantly.
Enter your numbers
Your results
| Item | Value |
|---|
Estimates based on your inputs — always confirm the recommended concentration in your owner's manual.
How to use this calculator
Find your cooling system capacity in quarts — it is listed in your owner's manual or repair guide. Enter that number, then enter the antifreeze concentration you want: 50% is the standard for moderate climates, and colder regions may call for a stronger mix.
The results update instantly as you type, showing exactly how many quarts of concentrated antifreeze and distilled water to combine. Concentrations above 70% are rejected because very strong mixes cool less effectively.
How this is calculated
Antifreeze = system capacity × (target % ÷ 100). Water = capacity − antifreeze. Use distilled water, and always check your owner's manual for the recommended concentration — the calculator accepts any ratio from 0–70%.
Worked example
12 qt capacity at 50% → 12 × 0.50 = 6 qt concentrate + 6 qt distilled water.
Reference data
No external dataset applies — this is pure ratio math on the numbers you enter. No tables, rates, or year-specific figures are used; the only constant is your own input.
Method & sources
Plain words: the calculator splits your system capacity into concentrate and distilled water using the percentage you choose. Every number on the page comes from your inputs — nothing is pulled from an external table.
- All figures are computed from the values you enter, in your browser — no external data sources are used.
- The 0–70% concentration limit follows common antifreeze practice stated on the page; check your owner's manual for your vehicle's recommendation.
Frequently asked questions
Is 50/50 the best coolant mix?
It is the standard recommendation for moderate climates, but always check your owner's manual — the calculator lets you enter any concentration.
Should I buy premix or concentrate?
This calculator assumes concentrated antifreeze. If you buy 50/50 premix, just pour it straight into the cooling system.
Distilled or tap water?
Distilled. Minerals in tap water can cause scale and corrosion in the cooling system.
Can I use this for a top-off?
Yes — enter the amount you need to add as the capacity and your target concentration.