DIY Cost Tools
Windshield Washer Fluid Mix Calculator
Split a desired batch volume into washer-fluid concentrate and water from a product’s stated parts ratio.
How to use this calculator
- Replace every example value with your own measurements, label values or planning assumptions.
- Keep each value in the unit printed beside its field.
- Select Calculate, then compare the result with the formula and limitations below.
Formula and method
Concentrate volume = final volume × concentrate parts ÷ total parts. Water volume = final volume × water parts ÷ total parts. One US gallon equals 128 US fluid ounces.
Results are hidden whenever an input changes or validation fails, so an older answer cannot be mistaken for the current calculation.
Worked example
Final batch volume = 1 US gal; Concentrate parts = 1 parts; Water parts = 3 parts. The calculator returns Concentrate = 32 US fl oz; Water = 96 US fl oz; Concentrate = 946 mL.
The worked example uses the same default values displayed in the calculator.
Limitations and safety
Frequently asked questions
What should I enter first?
Start with measurements or rates from the project, product label, service quote or equipment specification. Replace every example value before relying on the estimate.
Why can the real result differ?
Follow the concentrate label exactly, especially for freeze protection and material compatibility. Never substitute engine coolant or household chemicals, and keep automotive fluids away from children and pets.
Does the calculator round purchases up?
Only outputs labeled as whole packages, vents, heaters, pails or similar counts are rounded up. Keep extra precision for planning and follow supplier packaging.
Review notes and reference
Reviewed October 5, 2026. The formula was independently checked against the displayed default example, and the calculator was tested for valid defaults, empty input, invalid formats, range boundaries and recovery. Reference: NIST SI Units. Explanations and examples are original.