How to Dilute 90 Alcohol to 70: A Simple Guide

Diluting alcohol is a common practice for many reasons. It is used in many industrial settings, as well as in hospitals and laboratories. In the context of the COVID-19 pandemic, many individuals have also found it necessary to dilute alcohol for use as a disinfectant. One of the most common dilutions is to convert 90% alcohol to 70%. If you need to dilute 90 alcohol to 70, read on for a simple guide.

Why Dilute Alcohol?

Alcohol that is not diluted is often too strong to use in certain applications, such as disinfection. It can also be dangerous to handle and can cause irritation or burns. Diluting alcohol to a lower concentration is safer to handle and is still effective for most uses.

What is 90 Alcohol?

When referring to alcohol, the percentage indicates the concentration of ethanol in the solution. 90 alcohol means that the solution contains 90% ethanol and 10% water. This is also known as denatured alcohol, as it contains additives that make it unsuitable for drinking.

What is 70 Alcohol?

70 alcohol is a solution that contains 70% ethanol and 30% water. It is a common concentration for many uses, including disinfection and cleaning. It is also less harsh on the skin than stronger concentrations of alcohol.

Supplies Needed to Dilute 90 Alcohol to 70

To dilute 90 alcohol to 70, you will need the following supplies:

  • 90 alcohol solution
  • Distilled water
  • A clean container
  • A measuring cup or beaker
  • A stirring rod or spoon

Step-by-Step Guide to Diluting 90 Alcohol to 70

Step 1: Clean your work area and supplies

Before starting, make sure your work area and supplies are clean and dry. This will prevent contamination of your alcohol solution.

Step 2: Determine the amount of 70 alcohol needed

Calculate the amount of 70 alcohol you need using the following formula:

Volume of 70 Alcohol = (Volume of 90 Alcohol x 0.7) / 0.9

For example, if you want to make 500 mL of 70 alcohol:

Volume of 70 Alcohol = (500 mL x 0.7) / 0.9 = 388.89 mL

Step 3: Measure the 90 alcohol and distilled water

Using a measuring cup or beaker, measure out the amount of 90 alcohol needed. Then, measure out the amount of distilled water needed to reach the desired volume of 70 alcohol.

Step 4: Combine the 90 alcohol and distilled water

Pour the measured 90 alcohol into the clean container. Slowly pour in the measured distilled water while stirring the solution with a rod or spoon. Continue stirring until the solution is fully mixed.

Step 5: Label and store the 70 alcohol solution

Label the container with the date and concentration of the solution. Store the solution in a cool, dry place out of direct sunlight.

Safety Precautions When Handling Alcohol

When handling alcohol, it is important to take the following safety precautions:

  • Wear protective gloves and eyewear
  • Work in a well-ventilated area
  • Avoid creating sparks or flames
  • Do not mix alcohol with other chemicals, especially chlorine-based ones, as it can create toxic fumes


Q: Can I use tap water instead of distilled water?

A: It is not recommended to use tap water, as it may contain impurities that can affect the dilution process. Distilled water is pure, and therefore a safer choice.

Q: Can I dilute alcohol to a different concentration?

A: Yes, you can dilute alcohol to different concentrations depending on your needs. Use the same formula in Step 2, but substitute the desired concentration for 70 alcohol.

Q: Can I dilute alcohol that is not denatured?

A: It is not recommended to dilute alcohol that is not denatured, as it may be unsafe to handle or consume in high concentrations.


Centers for Disease Control and Prevention. (2021). Cleaning and Disinfection for Households. Retrieved from

World Health Organization. (2020). Guide to Local Production: WHO-recommended Handrub Formulations. Retrieved from

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