Acne Severity Scale Explained: Mild, Moderate and Severe Acne

Acne severity scales sort acne into mild, moderate and severe. Mild acne is mostly blackheads and whiteheads with a few small pimples, moderate acne has many inflamed papules and pustules, and severe acne adds deep nodules or cysts and often scarring. One common lesion-count rule calls fewer than 30 total spots mild, 30 to 125 moderate and more than 125 severe.

Below we explain the scales dermatologists and drug trials actually use, why the "grade 1, 2, 3, 4" numbers don't mean the same thing everywhere, how apps estimate severity from a photo, and the point at which home care should hand over to a dermatologist.

What do mild, moderate and severe acne look like?

The grades describe both how many spots you have and how deep they go. DermNet, the dermatology reference, describes acne as a mix of open and closed comedones (blackheads and whiteheads), inflamed papules and pustules and, in severe acne, nodules and pseudocysts, often followed by red or dark marks and scars.

• Mild: mostly blackheads and whiteheads, with a scattering of small red bumps or pus-filled spots. DermNet puts mild acne at a total lesion count under 30.
• Moderate: many inflamed papules and pustules, often across more of the face. DermNet's range is 30 to 125 total lesions.
• Severe: more than 125 lesions by DermNet's count, or deep, painful nodules and cysts that can leave scars.

Depth can outweigh numbers. A face with only a handful of deep, painful nodules is treated as more serious than a face with dozens of blackheads. If you're not sure which bumps are which, our guide to papules vs pustules shows how to tell them apart.

What acne grading systems do dermatologists use?

There's no single official scale. The FDA's guidance for acne drug trials says plainly that there is no single, standardized grading system for severity of acne. Instead, a few families of methods are used, often together.

The IGA and GEA labels come from a summary in a 2019 study of acne grading from smartphone photos, which describes the US IGA as having up to five ordinal grades and the European GEA as running from 0 to 5. The Japanese cutoffs come from a study that found dermatologists' overall severity grades correlated with the number of inflamed papules and pustules, but not with the number of comedones.

What is the IGA scale for acne?

The IGA is a single overall grade a clinician gives after looking at your face. The FDA recommends that trial IGA scales have approximately five severity grades, reported in whole numbers such as 0 to 4, with each grade defined by a distinct description of what the skin looks like. The definitions deliberately leave out lesion number ranges, because the IGA is meant to be a qualitative assessment.

In trials, treatment success on the IGA means reaching clear or almost clear (grade 0 or 1) with at least a two-grade improvement from baseline. The FDA also recommends pairing the IGA with lesion counts, since a drop in counts doesn't account for the size of lesions, how inflamed they are or where they sit, while the IGA considers both the quality and quantity of lesions.

What do acne grade 1, 2, 3 and 4 mean?

It depends on the scale, which is why the numbers are confusing online. On the IGA, grade 1 means almost clear and grade 4 means severe. On the European GEA, grade 4 is severe and grade 5 is very severe. Some older and regional systems number their grades differently again, so a "grade 2" from one source can describe different skin from a "grade 2" in another.

The practical fix is to use the words. Ask your clinician which scale they used, or describe your skin in terms that travel well: how many inflamed spots, whether there are nodules, and whether you're scarring.

How bad is my acne? How to estimate your own grade

You can get a rough sense at home with a careful count. Use a mirror in good daylight and work through these steps:

1. Pick one half of your face, forehead to jaw, and count the red, raised spots and the spots with a white or yellow center. This matches the half-face count in the Japanese classification: 0 to 5 mild, 6 to 20 moderate, 21 to 50 severe, more than 50 very severe.
2. Count blackheads and whiteheads separately. Trials count and report inflammatory and noninflammatory lesions separately, partly because some treatments target only one type.
3. Feel for deep lumps. A firm, painful bump under the skin may be a nodule, and nodules point toward severe acne whatever your count says.
4. Look for scars, including pitted marks and raised scars.
5. Check your chest, shoulders and back. The face-only scales don't capture these, and widespread acne usually needs more than spot treatment.

Write the counts down and repeat them every few weeks. A trend is more useful than any single grade. Our guide on how to track acne progress covers the photo and diary side.

How do apps estimate acne severity from photos?

Apps that grade acne use computer vision trained on photos that dermatologists have already graded. The best of them come close to expert agreement, with clear limits.

The most detailed published example trained an algorithm on 5,972 smartphone images from 1,072 acne patients, each graded by three dermatologists on the GEA scale. In its final version, the algorithm's GEA grading reached 68% agreement, similar to the dermatologists. It was much better at finding inflamed lesions than small comedones, with F1 scores of 84% for inflammatory lesions and 61% for non-inflammatory lesions. Several of the authors were employees of, or consultants to, a skincare brand.

Photo grading by people shows a similar pattern. When the same dermatologist assessed 69 patients in person and from their own iPhone photos, agreement was strong, with intraclass correlations of 0.81 for total lesion count and 0.75 for the IGA; the developers of the photo platform were among the authors. In an earlier study of digital acne images, the total inflammatory lesion count was the most reliable measure between raters, while agreement on the Leeds photographic grading technique was low.

What this means for you:

• Apps see red, raised spots best. Tiny closed comedones and flat bumps are easy to miss in a photo.
• Depth is hard to judge from a picture. A camera can't feel a nodule under the skin.
• Lighting and angle matter. Shadows can hide spots or create false ones, so take every photo the same way.
• Most apps only see your face. Chest and back acne need their own photos or an in-person check.

For more on what goes wrong, read how skin apps detect acne and why they miss some spots.

How can a selfie scan help you track acne between visits?

A consistent weekly photo record helps you and your dermatologist see whether acne is getting better. Pori doesn't assign a clinical acne grade. It takes a selfie and returns an overall skin score from 0 to 100 with a Pores & Texture score among its breakdowns, and its before/after comparison and progress charts let you watch how your skin's texture and overall look change from week to week. A skin diary for sleep, water, stress and diet sits alongside each scan, and your history stays on your iPhone, so you can show the series at an appointment.

Any app is a record of appearance. It isn't a diagnosis: it can't tell you what type of acne you have, feel a nodule or decide whether you need a prescription.

When should acne self-care give way to a dermatologist?

Book a dermatologist when acne is deep, scarring, not responding, or affecting how you feel. The American Academy of Dermatology recommends seeing one when acne causes cysts and nodules, hasn't cleared with treatment you can buy without a prescription, or makes you feel uncomfortable and you want clearer skin. It also advises giving a treatment time: if it works, you should notice some improvement in 4 to 6 weeks, and clearing can take two to three months or longer.

Grade matters for treatment options. The 2024 American Academy of Dermatology guidelines strongly recommend oral isotretinoin for acne that is severe, causing psychosocial burden or scarring, or failing standard oral or topical therapy, and DermNet lists referral to a dermatologist for severe acne. DermNet's treatment summary also adds prescription oral antibiotics for moderate acne, so it's worth an appointment if over-the-counter products haven't helped after a fair trial.

In practice, see a doctor if any of these apply:

• You have painful lumps under the skin, or new scars, at any count. Our guide to cystic acne explains why early treatment matters.
• Your half-face count of inflamed spots is regularly above 20.
• Two to three months of a consistent over-the-counter routine hasn't brought clear improvement.
• Acne is spreading to your chest and back, or leaving dark marks that linger.
• It's affecting your mood, sleep or social life.

Scarring is the main reason not to wait, because scars stay long after the breakouts that caused them. Our overview of acne scar types explains the main kinds.