Rubbing alcohol isn’t something you can practically make from scratch at home. It’s manufactured industrially by combining propylene (a petroleum byproduct) with water under high pressure and heat, using specialized catalysts and distillation equipment. What you can do at home is dilute higher-concentration isopropyl alcohol down to the percentage you need, or mix a sanitizing hand rub using store-bought ingredients. Both are straightforward with the right ratios.
How Rubbing Alcohol Is Made Commercially
Isopropyl alcohol is produced by reacting propylene, a gas derived from petroleum refining, with water in a process called hydration. Industrial facilities run this reaction at roughly 290 psi of pressure inside catalytic distillation columns, producing isopropyl alcohol at purities up to 99.9%. The United States Pharmacopeia (USP) requires pharmaceutical-grade isopropyl alcohol to contain at least 99.0% pure alcohol, with methanol limited to no more than 0.02% and total impurities capped at 1.0%.
This process requires industrial chemistry equipment, high temperatures, and pressurized reactors. There’s no safe or realistic way to replicate it in a home setting. The rubbing alcohol you buy at the pharmacy is this industrial product diluted with purified water to 70% or 91% concentration.
Why You Can’t Distill It at Home
Some people wonder about distilling alcohol as a workaround. Even setting aside the legal issues with unlicensed distillation, the safety risks are severe. Poor distillation practices have caused deaths throughout history, primarily from methanol contamination. Methanol is a toxic byproduct that’s difficult to separate without proper equipment and monitoring. A study of home-distilled spirits in Romania found methanol in 74% of samples tested, with nine samples exceeding U.S. legal limits.
Methanol is dangerous in small amounts. Concentrations above 200 mg/L in the body can damage vision and cause blindness. Above 2,000 mg/L, it causes liver and kidney damage. Acute toxicity around 5,000 mg/L leads to loss of consciousness and death. Between 1963 and 2020, toxic methanol incidents worldwide caused over 2,243 fatalities. Even if you were attempting to make ethanol rather than isopropyl alcohol, the methanol risk alone makes home distillation a genuinely dangerous idea.
Isopropyl alcohol also has a flash point of just 53°F to 57°F, meaning its vapors can ignite at room temperature. It carries a flammability rating of 3 out of 4 on the NFPA hazard scale. Working with concentrated alcohol vapors near any heat source, spark, or open flame creates a serious fire and explosion risk.
How to Dilute 99% Isopropyl Alcohol to 70%
The most practical thing you can do at home is buy 99% isopropyl alcohol (available at pharmacies and chemical suppliers) and dilute it to 70%, which is the concentration that works best as a disinfectant. Higher concentrations actually kill bacteria less effectively because they evaporate too quickly. The extra water in a 70% solution helps it penetrate cell walls and dissolve organisms more thoroughly. Disinfecting power drops noticeably above 80% to 85% concentration.
The ratio is simple: mix 7 parts 99% isopropyl alcohol with 3 parts distilled water. For precise measurements:
- To make 1 liter of 70% rubbing alcohol: combine 707 mL of 99% isopropyl alcohol with 293 mL of distilled water.
- To make 500 mL: combine 354 mL of 99% isopropyl alcohol with 146 mL of distilled water.
- Starting with 91% instead of 99%: mix 770 mL of 91% isopropyl alcohol with 230 mL of distilled water per liter.
Use distilled or boiled-and-cooled water rather than tap water. Tap water can contain minerals or microorganisms that reduce the shelf life or effectiveness of your solution. Stir or gently shake to combine, then store in a clean, labeled container.
The WHO Hand Sanitizer Formula
If your goal is making a hand sanitizer rather than a general-purpose rubbing alcohol, the World Health Organization published a formula specifically designed for situations where commercial sanitizer isn’t available. It uses isopropyl alcohol as the active ingredient along with two other common ingredients.
To make 1 liter of the WHO formulation, pour the following into a graduated container in order:
- Isopropyl alcohol (99.8% purity): 751.5 mL
- Hydrogen peroxide (3% concentration): 41.7 mL
- Glycerol (98% concentration): 14.5 mL
- Distilled or boiled-and-cooled water: enough to reach the 1,000 mL mark
The hydrogen peroxide isn’t there to disinfect your hands. It kills any bacterial spores that might be present in the container or raw ingredients. The glycerol acts as a moisturizer to prevent your skin from drying and cracking with repeated use. Shake gently to mix. The WHO recommends letting the mixture sit for 72 hours before use to allow the hydrogen peroxide to neutralize any contaminating spores.
An ethanol-based version also exists: 833.3 mL of 96% ethanol replaces the isopropyl alcohol, with all other ingredients and quantities staying the same. That version produces a final ethanol concentration of 80%.
Storing Rubbing Alcohol Safely
Whether you’ve diluted your own solution or bought it off the shelf, rubbing alcohol requires careful storage. Keep it in a tightly sealed container in a cool, well-ventilated area away from direct sunlight. Because its vapors ignite at temperatures as low as 53°F, never store or use it near open flames, stoves, space heaters, or anywhere someone might be smoking. Even static electricity can ignite concentrated vapors in a poorly ventilated space.
Rubbing alcohol is toxic if swallowed. Ethanol-based rubbing alcohol products are required by federal law to contain denaturants, bitter or toxic additives that make them undrinkable. Common denaturants include denatonium benzoate (one of the most bitter substances known), methanol, acetone, and quinine sulfate. Isopropyl alcohol doesn’t need added denaturants because it’s inherently toxic to drink, but it should still be stored out of reach of children and clearly labeled.