Glycolic Acid: Which % Should You Use? (+ Calculator)

Last reviewed: 2026-10-06 · by Rodger (pen name), editor

You're staring at two glycolic acid products. One says 7%. The other says 30%. They cost about the same. So the 30% is obviously better — more acid, more results, right?

Not necessarily. No source we read says a higher glycolic acid percentage is better. What the sources do say is that strength depends on more than the label: a review of glycolic peels states that the higher the concentration and the lower the pH, the more intense the peeling (Sharad 2013). By our own free-acid arithmetic below, the pH of the formula can even make a 7% product deliver more free acid than a 20% one.

This guide maps every concentration tier from 2% drugstore cleansers to 70% clinical peels, sets out what the sources say about each one, and gives our own working view of where to start. Once you've picked a strength, our how to use glycolic acid guide covers the application mechanics — timing, frequency, and what to layer it with.

Why the Number on the Label Doesn't Tell the Full Story

Before we break down each percentage, you need to understand one critical concept: free acid value.

The percentage on a glycolic acid product tells you the total amount of glycolic acid in the formula. Not all of it is in free (un-neutralized) form, and the free fraction depends on the product's pH. The tables and calculator on this page are our own arithmetic, not cited findings.

Values calculated with the Henderson–Hasselbalch equation at glycolic acid's pKa of 3.83 — the same math the calculator below uses. Real formulas can deviate with heavy buffering systems, but the pattern holds.

Notice that a 10% product at pH 4.5 delivers less free acid than a 7% product at pH 3.0. By this arithmetic, two products with the same labeled percentage can differ several-fold in free acid. One small trial shows why the label alone is a poor guide: a randomized trial in 80 acne patients (Zhao 2022, a letter) compared a 5% glycolic acid complex applied daily with 20% glycolic acid in four clinic sessions two weeks apart. Both improved; the 5% complex group did better on total and inflammatory lesions, lesion severity, skin hydration and satisfaction, while the 20% group had a better pore score and higher transepidermal water loss. The 5% product was a complex containing other ingredients, and the participants had Fitzpatrick skin types IV–VI, so it cannot be generalised (abstract and letter text read).

The practical takeaway, in our reading: the label percentage and the pH together say more about strength than either alone. Cleveland Clinic's source says glycolic acid, as the smallest AHA, can penetrate skin more easily than other acids (Cleveland Clinic); see our lactic acid comparison and vitamin C comparison for how glycolic acid sits beside them.

Free Acid Calculator: Estimate What Your Product Delivers

Enter any product's labeled concentration and pH, and this calculator estimates the free acid — the share of glycolic acid left un-ionised at the product's pH — using the Henderson–Hasselbalch equation at glycolic acid's pKa of 3.83. If the brand doesn't publish pH (most don't — see our disclosure statistics), Medical News Today says most over-the-counter products have a pH of around 4, and the brands in our catalogue that do publish a pH list ranges of roughly 3.4 to 4.0. The method is not ours: cosmetic chemist Michelle Wong published a free acid calculator for exfoliants on Lab Muffin Beauty Science in June 2016, covering glycolic, lactic, mandelic, salicylic and four other acids. What this page adds is the same calculation applied to every product we list, from each brand's own published pH.

Honest caveats: this is textbook chemistry, not a lab measurement. Heavily buffered systems, time-release carriers, and partially neutralized formulas can deviate from the simple equation, and skin response also depends on contact time and the rest of the formula. A brand that publishes free acid value directly is a better guide — our catalogue records Glytone's Mild Cream Cleanser as 3.4% free acid value, for example. Treat the calculator as an estimate for comparing products, not a certificate of analysis.

Concentration Tiers: What Each Range Does

Where we would start: a 2–5% rinse-off cleanser to see how skin tolerates glycolic acid, then a 5–7% leave-on toner. This is our working view, not a sourced recommendation: Cleveland Clinic quotes advice to start once or twice a week and work up if skin tolerates it, and Medical News Today suggests beginners look for around 8%. Hold off on anything above 10% until you have built tolerance; the CIR panel's consumer figure is 10% or less (FDA). The tiers below follow the ladder chart further down, and for each we say what the sources do and do not show.

Under 5%: The Gentle Introduction

Found in: Cleansers, gentle toners, daily moisturizers

What the sources show: A 5% daily cream improved texture and discoloration significantly over 3 months in a 75-person placebo-controlled trial, with no significant wrinkle change (Thibault 1998). In our reading, a rinse-off cleanser at this strength spends little time on skin, though no source measures that.

Our view: A reasonable first step for people new to AHAs or with sensitive skin. Cleveland Clinic's source advises caution with glycolic acid if you have sensitive skin, dry skin, rosacea, eczema or an active skin infection.

L'Oréal's glycolic cleanser at 3.5% is the entry-level option in our catalogue. We found no trial of it, and a rinse-off format does not remove the need to stop if skin reacts.

5-8%: The Daily Driver

Found in: Toners, lightweight serums, essence products

What the sources show: Nothing we read tested a 7% product. The nearest evidence is the 5% daily cream above and a 10% glycolic plus 2% phytic acid emulsion that improved hyperpigmentation, texture and tone from week 4 through week 12 (Houshmand 2021). Cleveland Clinic's source says over-the-counter products may take several months of consistent use before pigmentation looks more even.

Our view: This is the range we would try after a cleanser. Start at once or twice a week, as Cleveland Clinic's source suggests, and work up only if skin tolerates it.

The Ordinary's 7% glycolic toner is a leave-on toner at this strength; the same sources apply, and no trial we read tested it. Start at 2 times per week.

If 7% feels like too much, Good Molecules' 3.5% glycolic toner sits at the low end of this range. See our sensitive skin guide for more on low-concentration options.

8-15%: The Targeted Treatment

Found in: treatment serums, peel pads, overnight masks

What the sources show: The 12-week Houshmand trial used a 10% product, and the CIR panel's consumer figure tops out at 10% (FDA). Medical News Today says glycolic acid used too frequently or at too high a concentration can cause irritation or damage (Medical News Today). Healthline reports Cleveland Clinic advising against products above 15 percent AHA (Healthline). We found no source on how often to use products in this range.

Our view: Not a beginner range. If you step up, a lower frequency than your current product (for example 1-2 times per week for a leave-on) is our working schedule, not a sourced one. A peel pad should follow its own directions, which may not be daily.

The INKEY List's 10% glycolic acid toner is the highest-concentration toner in our product catalogue. We found no trial of it.

Thicker, friction-prone body skin may be treated differently from the face. We found no source comparing tolerance, and our guide to rough elbows, knees, and heels gives our working ranges for those areas, labelled as ours.

15-20%: The Bridge Zone

Found in: At-home peel kits, intensive treatment serums, professional-strength pads

What the sources show: DermNet NZ describes glycolic acid peels as 20 to 70% strength, and a review says the usual starting concentration in clinic is 20% (Sharad 2013). We found no source evaluating at-home 15-20% kits, so we cannot say how often they can be used or what to expect.

Our view: Treat this tier with the caution the sources give for peels: neutralise on time, watch for frosting, and stop if skin burns. SPF matters, since the FDA's studies found increased UV sensitivity with AHA use.

20-50%: Professional Peel Territory

Found in: Professional chemical peels administered in dermatology offices and medical spas

What the sources show: A review states that peel depth depends on the concentration, the number of coats and the time applied, so glycolic acid can act as a very superficial peel or even a medium-depth peel (Sharad 2013). It summarises a 2009 classification (Fabbrocini) of very superficial peels at 30-50% applied for 1-2 minutes and superficial peels at 50-70% applied for 2-5 minutes. In a double-blind trial, 50% glycolic acid applied for 5 minutes once weekly for 4 weeks improved rough texture and fine wrinkling and slightly lightened solar lentigines (Newman 1996). A 2022 trial used 20% in four clinic sessions two weeks apart (Zhao 2022).

Frequency in the sources: The review describes repeating peels once every 15 days for 4-6 months until the desired result is achieved, and the 2022 letter describes clinic peels at 2-4 week intervals. Your provider sets the schedule.

50-70%: Clinical Peels

Found in: Dermatology offices; 70% gel peels are also sold online

What the sources show: The review summarises the 2009 classification as superficial for 50-70% applied for 2-5 minutes and medium depth for 70% applied for 3-15 minutes, with the provider watching for frosting and neutralising immediately if it appears (Sharad 2013). The same review says glycolic acid peels have been found very safe in Fitzpatrick skin types I-IV; we found no source in this session on higher skin types beyond the 2022 trial of 20% in types IV-VI. We found no source for downtime lengths, so we do not give them.

The Concentration Ladder: How to Progress Safely

Think of glycolic acid percentages as a ladder, not a menu. You don't pick the highest rung and jump — you climb one step at a time.

Percentage and frequency are the two dials on this ladder; in our reading a stronger product warrants a lower starting frequency. For the frequency half of that equation on its own, including how it differs by product format and how to tell you've gone too far, see our dedicated guide to how often to use glycolic acid.

Quick Reference: Every Concentration at a Glance

This table is our own working summary. The frequencies are our suggested schedules, not trial results. The sourced limits are the CIR panel's consumer figure of 10% or less at pH 3.5 or higher (FDA) and DermNet NZ's description of 20-70% as peel strength (DermNet NZ).

Common Mistakes When Choosing a Percentage

Mistake #1: Starting at the highest concentration you can buy. Medical News Today says glycolic acid used at too high a concentration can cause irritation or damage (Medical News Today), and the FDA's adverse-event summary lists burning, blisters and pigmentary changes, most often with skin peelers (FDA). Our suggestion is to start at 2-5% and work up. If you're already dealing with stinging, redness, or peeling from a concentration that's too strong, our guide to glycolic acid side effects covers what's normal, what to change, and when to see a doctor.

Mistake #2: Assuming higher percentage = better results. In our reading, a product you can use consistently is a better bet than one that irritates you into stopping; no source compares them. Cleveland Clinic's source also suggests avoiding retinol and other exfoliants when first starting glycolic acid (see our retinol comparison).

Mistake #3: Ignoring pH. A 10% glycolic product at pH 4.5 delivers less than half the free acid of a 5% product at pH 3.0 (about 1.8% vs 4.4% — check any combination in the calculator). If a product doesn't list its pH, the percentage alone is only half the picture by this arithmetic.

Mistake #4: Using professional-strength peels at home without experience. Products at 30%+ are sold online, and our catalogue lists them. The FDA's adverse-event summary lists chemical burns, blisters and pigmentary changes for AHA products, most often peels (FDA), and the peel review stresses timing and neutralisation on time (Sharad 2013). We advise against home use.

Mistake #5: Skipping concentration tiers. Jumping from a 5% toner straight to a 20% peel skips the middle tiers. Our suggestion is to step up gradually; the review recommends starting a peel course at 20% and increasing over sessions (Sharad 2013), and no source tests skipping tiers.