Alcohol Dilution Calculator
The Alcohol Dilution Calculator tells you how much of a strong spirit and how much water to mix to reach a target alcohol strength. It uses the dilution rule C₁V₁ = C₂V₂, so original volume = (desired % × final volume) ÷ original %.
Formula
C1V1 = C2V2
- The dilution law states that concentration × volume is conserved: original % × original volume = desired % × final volume.
- Rearranged: original volume = (desired % × final volume) ÷ original %.
- Water to add = final volume − original volume.
- Mixing alcohol and water causes a slight volume contraction, so for precise spirits work proof by weight or check the strength after mixing.
Example Calculation
Inputs
- Original Concentration %: 95
- Desired Concentration %: 70
- Final Volume (mL): 100
To make 100 mL of 70% solution from 95% alcohol: original volume = (70 × 100) ÷ 95 ≈ 73.7 mL of alcohol, topped up with about 26.3 mL of water.
Frequently asked questions
How do I dilute alcohol to a target strength?
Use C₁V₁ = C₂V₂: the volume of strong alcohol needed is (desired % × final volume) ÷ original %, with the rest made up by water.
How much water should I add?
Subtract the calculated alcohol volume from the final volume; the difference is the water to add.
Can I use this to make 70% sanitizer?
Yes. Enter the original concentration (e.g. 95%), a desired 70%, and your target final volume to get the mix.
Why isn't the mixed volume exact?
Alcohol and water contract slightly when combined, so the real final volume can be marginally less than the sum of the parts.
Does temperature matter?
Alcohol strength is usually specified at 20°C; large temperature differences can slightly affect volume-based measurements.