Contractor Job Estimator
$29.00
BuyCoolant Mix Ratio Calculator
Quarts and liters of antifreeze concentrate and distilled water for a target mix or freeze point — ethylene glycol / water at 15 psi, fresh fill or top-off
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How to Use This Coolant Mix Calculator
Look up total cooling-system capacity in the owner’s manual. Choose quarts or liters. Pick a target 50/50-style ratio or enter a freeze-protection goal for your climate. For a partial refill, switch to top-off mode and enter the current refractometer reading. Calculate. Verify with a refractometer before you close the cap.
Fresh fill: concentrate = capacity × r, water = capacity × (1 − r)
Adjust up (r > c): drain & replace concentrate = capacity × (r − c) / (1 − c)
Adjust down (r < c): drain & replace water = capacity × (c − r) / c
r = target concentrate fraction; c = current concentrate fraction
Adjust up (r > c): drain & replace concentrate = capacity × (r − c) / (1 − c)
Adjust down (r < c): drain & replace water = capacity × (c − r) / c
r = target concentrate fraction; c = current concentrate fraction
Worked example — 12 qt system, 50/50 fresh fill
Capacity 12 qt at 50% concentrate → 6.00 qt concentrate + 6.00 qt distilled water. Interpolated freeze protection −34°F (−37°C), boil at 15 psi 265°F (129°C).
Why the curve behaves this way: guide. Overheating from bad mix: troubleshooting.
Coolant Mix FAQ
Why is there no chart page?
Mix math is capacity × ratio with interpolated freeze/boil checks. The widget, guide, and a refractometer already give you what a static chart would.
Can I use tap water?
Distilled water for mixing concentrate. Tap water adds minerals that accelerate corrosion and can skew refractometer readings.
Pre-mixed 50/50 or concentrate?
See pre-mixed vs concentrate. Bottled 50/50 is exact but costlier per gallon; concentrate lets you tune for colder climates.
Where are recommended product links?
Affiliate product cards for refractometers and coolant are pending sourcing in the live CSV. Use the calculator and guide now; product picks will appear when sourced.