What Does the Grammarly AI Detector Percentage Mean?

The percentage you see from an AI checker such as Grammarly's is best read as an estimate of how much your text resembles machine-written text, not as a measurement of how much of it a machine wrote. It cannot tell you who typed the words, and it can be wrong in both directions. Use it as a prompt to look closer at your writing, not as a verdict.

Detectize is independent and not affiliated with Grammarly. Grammarly is mentioned here only to describe a tool many students use. We can't see inside it, so this article explains how AI detectors generally work and how to read their scores.

Short answer

• The number is a statistical guess about wording, not a record of how the text was produced.
• A high number means "this looks like patterns we associate with AI". A low number means the opposite. Neither is proof.
• Many people read "30%" as "30% of my essay was AI-written". Detectors generally don't report it that way, so check the tool's own explanation next to the number.
• If the number worries you, keep your drafts, look at which sentences were highlighted, and get a second opinion.

How an AI checker produces a number

AI detectors don't know who wrote a text. They look at the wording and estimate how closely it resembles text produced by language models. Roughly, they consider how predictable the word choices are, how even the sentence structure is, and how much the text varies from sentence to sentence. Those signals are combined into a likelihood or a share, and shown as a percentage.

Two things follow from that:

1. It is built on resemblance. Writing that is clear, tidy and formal can resemble machine text even when a person wrote every word.
2. The same text can get different numbers elsewhere. Different tools use different methods, so scores from different checkers do not line up. A "20%" in one tool is not the same thing as "20%" in another.

Common ways to misread the percentage

"It means that share of my essay is AI." Not necessarily. Many tools report how confident they are about the text or about passages, not an exact count of AI words. Read the tool's own wording.

"Under a certain number is safe." There is no universal safe number. How a result is used depends entirely on the person reading it, such as your instructor or editor, and on your school's policy. We can't tell you where any particular reader draws the line.

"A high number proves cheating." It doesn't. Detection is probabilistic, and false positives are a known limit of the whole category.

"A low number proves I'm fine." Also no. Detectors can miss AI-written text, so a low score is not a certificate.

Why your own writing can score high

Some common reasons a human-written essay looks "AI-like" to a program:

• Formal, neutral academic style with steady sentence length.
• Heavy editing with grammar or style tools, which smooths out individual quirks.
• Writing in a second language, where careful, simple, correct sentences read as uniform.
• Generic passages such as definitions, introductions and summaries.

If this describes your essay, a high number says something about the style, not about misconduct.

What to do with a percentage that worries you

1. Don't change or delete anything yet. Save a copy of the document as it is.
2. Look at the highlights. If the tool marks sentences, read them. They are often the most generic ones, and you can add your own specifics.
3. Compare with a second tool. If two checkers disagree, that shows how uncertain the number is. You can try our free AI detector for sentence-level highlights.
4. Gather your evidence. Version history, outlines, notes and sources show how the essay was made. Our guide on how to prove you didn't use AI explains what counts.
5. Talk to your instructor if they raised it. Offer to walk through your argument and sources instead of debating the number.

If the flag has already happened and you wrote the essay yourself, see Grammarly says my essay is AI but I wrote it for a step-by-step plan.

How to use a detector sensibly before you submit

• Check a full section or the whole essay. Very short samples give a tool less to go on.
• Read the highlighted sentences instead of focusing only on the headline number.
• Where a passage is generic, add something that only you could write: a specific example, a detail from a source, your own reasoning.
• Keep your drafts and version history running while you work.

A result from Detectize, like one from any detector, is an estimate. It can't certify anything to a teacher or school, and we don't claim it is more accurate than any other tool. We also don't store the text you paste.

Other checkers report scores differently, so see how the Scribbr AI detector and the Copyleaks AI detector work too. If the flag came from Grammarly and you wrote the essay yourself, the TypeSafe comparison in TypeSafe's Jev detector test also shows how uncertain these numbers can be.

FAQ

What percentage of AI is acceptable?

There isn't a universal answer. It depends on your instructor, your institution's policy, and the assignment. Ask how detector results are used in your class instead of guessing at a threshold.

Is the percentage the share of words written by AI?

Not necessarily. Detectors generally report a likelihood or an estimate about the text. Check how the tool describes its own number.

Why do two AI checkers give me different percentages?

Because they use different methods and are tuned differently. Disagreement is normal, and it is a good reminder that no single score is final.

Can I get a 0% score?

You can't guarantee any score, and trying to game one isn't a good use of time. A better goal is writing that is clearly yours: specific, well sourced, and backed by drafts you can show.

Can an AI detector be wrong?

Yes, in both directions. It can flag human writing and miss AI text, which is why drafts and version history matter more than any number.