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Diluting Isopropyl Alcohol



With the sharp rise in Coatings (ie Optimum Opti-Coat, 22ple, etc.) that require a properly prepped surface we have been receiving more questions about how you dilute isopropyl alcohol (aka IPA) correctly. One of the most popular bottles you can pick up contains a ratio of 70/30 (Alcohol to Distilled Water), which can make the math a bit challenging if you want to dilute it. While it is generally okay to use it at the 70/30 ratio, many detailers prefer to dilute it down to a 50/50 (Alcohol to Distilled Water) ratio for optimal results.  If you don’t want the boring details skip to the pictures and chart at the end of the article. For those who want to know the exact math behind the dilution we did our best to break it down very simply so please keep reading.

Using the following formula, .7 represents the 70% isopropyl alcohol you have and .5  represents the 50% we want to end up with.  Therefore our formula to determine the appropriate percentage of alcohol is:

.7x = .5 = .7143 or 71.43%

In conclusion x = 71.43 or 71.43%.  So no matter what size bottle you have fill 71.43% of it with the 70/30 mix of isopropyl alcohol and the rest with water.  If you want to determine the percentage of water just take the difference between the 71.43% and a full bottle which is represented by 1.

1 – .7143 = .2857 or 28.57%

Each bottle should then contain 28.57% distilled water no matter what size the bottle is.  Below are the DI Accessories Isopropyl Alcohol and 2 bottle sizes of our DI Accessories Trigger Spray Bottles (22oz, and 32oz). Each bottle is marked with a black line to where this 28.57% of each bottle is located.


You are now going to want to fill each bottle to this line with water. We used some blue food coloring to help highlight the water for picture purposes.


After filling the bottle with 28.57% distilled water fill the rest of the bottle with a 70/30 isopropyl alcohol.

You now have a bottle of 50/50 isopropyl alcohol mix to help remove old protection and ensure you have a clean surface!  You can also take a look at the table below for complete dilution information on multiple size bottles!

Diluting Isopropyl Alcohol (70/30 to 50/50)
Bottle Size % Of Water (Distilled) Ounces Of Water (Distilled) % Of Isopropyl Alcohol (70/30) Ounces Of Isopropyl Alcohol (70/30)
8 Ounces 28.57% 2.3 Ounces 71.43% 5.7 Ounces
12 Ounces 28.57% 3.4 Ounces 71.43% 8.6 Ounces
16 Ounces 28.57% 4.6 Ounces 71.43% 11.4 Ounces
22 Ounces 28.57% 6.3 Ounces 71.43% 15.7 Ounces
32 Ounces 28.57% 9.1 Ounces 71.43% 22.9 Ounces
64 Ounces 28.57% 18.3 Ounces 71.43% 45.7 Ounces
128 Ounces 28.57% 36.6 Ounces 71.43% 91.4 Ounces

Hopefully this information was helpful in answering some of your questions about diluting isopropyl alcohol!

14 comments on Diluting Isopropyl Alcohol

  1. Brad W. says:


    Now you post this cheat sheet after I did the calculations myself last weekend…Thanks a lot. Seriously, this will help some folks for sure. Thanks for the article Reece, no matter how “late” it was. Just printed the chart out too. Thanks again.

  2. David B says:

    Thank you SO much for this “cheat sheet” Reece – was actually wondering about this when it came time to applying 22ple – not as good at math as Brad W. is I guess. LOL

    Am lucky enough to be a future student at the Esoteric Detail Academy – one LESS question to ask Todd!!!

  3. Albert says:


    This is kind of funny, because it’s a fun use of algebra. It’s the right way to do it.

    I used to estimate by figuring; 70% (alcohol) x some number = 50%. I’d arrive at ~.71 and .~29 for water, and then I’d round it to 70% and 30%.

  4. Adam B says:

    Very helpful, I always looked for the highest percentage bottle of IPA on the shelf but still at 90% I never took into consideration that last 10% so I was really at about 60% water 40% IPA.

  5. Richard says:


  6. Dave says:

    I need a 60% alcohol. If I would mix 4 oz of 50% and 4 oz of 70% would it in essence be a 60% mixture?

  7. Tony Parone says:

    In reducing 90% alcohol to 70%, would one add 20% distilled water for the reduction (90 – 20 = 70)?

    • Frank says:

      um, no… 500 mL of 91% alcohol would need to be mixed with 150 mL distilled water to be a 70% solution. That’s a 10:3 ratio

  8. Serena Dempsey says:

    HI clever people,

    How do I find out if 2% of Isopropyl Alcohol in a mixture is still considered a dangerous good? There are no other flammable ingredients.

    Basically, at what point does it become flammable? We have a few products with 2% ISO, and one with 3% and one with 5%. Need to know if we need to put flammable pictograms on them.

    Thank you xoxoxo

  9. Rhondi says:

    Can I mix 50% and 70% together? Does it make the alcohol % stronger or dilute it? I’m wanting to use it in painting effects. I’m terrible with math. Thank you for any tips.

  10. Howard says:

    Very useful DI. Thanks

  11. At what dilution level with water is a starting 70% rubbing alcohol no longer air flammable? I want to clean my carpets and I have a wood stove going. Don’t want to blow up.

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