Rubbing Alcohol Dilution Calculator: 91% or 99% to 70%

Stronger is not always better for cleaning: the CDC disinfection guideline says the optimum bactericidal concentration of alcohol is 60–90% in water, and that alcohol works less well below 50%.

Sources: CDC: chemical disinfectants (alcohol) (read 3 Nov 2026).

For cleaning surfaces only. Do not drink rubbing alcohol. Alcohol is flammable: mix away from flames and keep the bottle closed. Mixing alcohol and water shrinks the total volume slightly, so the result is approximate.

Why add water?

According to the CDC, proteins are denatured more quickly when water is present, so pure alcohol is less effective at killing bacteria than alcohol mixed with water.

Rubbing alcohol is poisonous to drink. Use it only as the label says.