Isopropyl Alcohol
Dilution Calculator
Use this page when the search started with "how to dilute 99 IPA to 70" or any IPA-to-working-strength question. It launches the main Alliance Chemical calculator with the right IPA stock loaded, explains why 70% is the disinfection sweet spot, and points to the right grade for your application.
Start With The Common IPA Jobs
Search Console shows the most common IPA dilution intent is stepping 99% down to 70% for disinfection. These launchers cover that plus the lower-water-content targets used for electronics and lab work.
99% → 70%
Open the calculator with 99% technical IPA loaded and the 70% disinfection target preset for a 1-gallon batch.
Open Preloaded Calculator Surface Clean99% → 50%
Launch a 1-gallon 50% IPA batch for general-purpose surface cleaning where faster evaporation matters more than dwell time.
Open Preloaded Calculator From 91%91% → 70%
Already stocking 91% USP? Launch the calc preloaded for 91% stock and a 70% target so the math isn't off by a few points.
Open Preloaded Calculator Quick Ratio1 : 0.414 Water
Use ratio mode when an SOP is written as parts-IPA-to-parts-water instead of a final percentage.
Open Preloaded CalculatorChoose The Right IPA Grade
Most IPA buying mistakes are spec mistakes, not concentration mistakes. Technical grade is fine for cleaning and degreasing; USP is what you want for any skin-contact, medical, or regulated environment.
70% USP is the ready-to-use disinfection strength. It is the concentration cited most often in CDC and infection-control guidance for surface wipe-downs because water is needed for the alcohol to penetrate cell membranes effectively.
91% USP is the middle tier. It is strong enough for lab and electronics use where less water is preferred, but close enough to 70% that a single dilution step gets you there without extreme ratios.
99% Technical is the concentrate for facilities that want one stock feeding multiple working strengths — 70% for disinfection, 50% for cleaning, or near-anhydrous for electronics. Technical grade keeps the price down when USP certification is not required.
A practical rule: buy 70% USP when that is what you use day-to-day and you do not want to dilute. Buy 99% when you need flexibility and your crew reliably does the dilution math (which this calculator will do for you).
Isopropyl Alcohol 70% USP Grade
Ready-to-use disinfection strength with USP pharmacopeial spec — skip the dilution step entirely.
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Isopropyl Alcohol 91% USP Grade
USP-grade middle tier for labs, electronics work, and teams that want less water than 70% without jumping to anhydrous.
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Isopropyl Alcohol 99% Technical Grade
Near-anhydrous concentrate for facilities diluting to multiple working strengths or needing low-moisture cleaning solvent.
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Common IPA Dilution Targets
These are the IPA working strengths customers ask about most often. Contact time, substrate, and regulatory context all matter, so verify against your SOP before scaling a batch.
| Starting Stock | Target | Typical Use | Notes | Launch |
|---|---|---|---|---|
| 99% isopropyl alcohol | 70% | Surface disinfection | The classic disinfection strength. 70% denatures proteins more effectively than higher concentrations because water extends dwell time. | Open |
| 99% isopropyl alcohol | 50% | General cleaning and degreasing | Faster evaporation and more residual rinse compared to 70%. Not a substitute for disinfection. | Open |
| 91% isopropyl alcohol | 70% | USP disinfection from 91% stock | Lower-dilution step for facilities already on 91% USP. Keeps pharmacopeial grade through the working solution. | Open |
| 99% isopropyl alcohol | 1:0.414 water | Ratio-mode SOP for 70% | One part 99% IPA to 0.414 parts water is the algebraic equivalent of 99% → 70%. Useful when your SOP is parts-based. | Open |
IPA Handling Reality Check
IPA is low-toxicity compared to many industrial solvents, but it is still a Class IB flammable liquid with a flash point around 12°C. Ignition, vapor pooling, and static discharge are the failure modes that actually cause incidents.
Flammable, not benign. IPA vapor ignites from a spark. Keep containers grounded when transferring, avoid open flames and heat sources, and ventilate enclosed spaces. Do not store 99% IPA near electrical panels or heaters.
70% is the sweet spot for disinfection — not higher. Pure 99% evaporates too quickly to penetrate cell walls. The water in 70% is what gives the alcohol time to do its job. Using 99% on a surface will feel more "sanitary" but is measurably less effective at killing microbes.
USP grade matters for skin-contact or medical contexts. Technical grade is fine for industrial cleaning. For wound prep, pharmacy compounding, or anything touching patients or food, verify the USP certification before substituting.
Dilute with distilled water when it matters. Tap water contains minerals and chlorine residues that can leave streaks on electronics, screens, and optical surfaces. For lab or cleanroom work, distilled or DI water only.
Related Internal Resources
Use these pages to compare acids, understand adjacent use cases, and route visitors deeper into the resource center instead of bouncing back to search.
Frequently Asked Questions
Visible answers that match the search intent this page is targeting.
FAQ
Why is 70% IPA better than 99% for disinfection?
How do I dilute 99% IPA to 70% at home?
Can I use 91% IPA instead of diluting 99%?
Does Alliance Chemical sell USP-grade IPA?
Need IPA In The Right Grade?
Buy 70% USP ready-to-use when disinfection is the only job. Step up to 91% USP or 99% Technical when you need flexibility or lower water content.