Active vs Passive Voice: Does Voice Change Your Grade Level?

Writing advice often says active voice makes text more readable. That may be true for readers. It is not true for readability formulas, because the formulas cannot see voice at all.

This post shows what the formulas count and what happens to the score when you switch a sentence from passive to active. Every score below comes from this site's calculator, run on 9 October 2026.

What the formulas count

The Flesch-Kincaid Grade Level comes from a 1975 US Navy study. The formula is:

Grade = 0.39 × (words per sentence) + 11.8 × (syllables per word) − 15.59

There is no term for voice. The same is true of Flesch Reading Ease, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. Each one uses sentence length plus word length, counted in syllables or letters.

So a change of voice can only move the score if it changes one of those counts.

Three pairs, scored

In the first pair, the active sentence is clearer and two words shorter. It also scores higher. In the second pair the scores are identical. In the third, the active version uses 21 words where the passive uses 28, and the grade barely moves.

Why the shorter sentence can score higher

Passive sentences add short words: "was", "by", "the". Those words have one syllable each. Take them out and the sentence gets shorter, which lowers the first part of the formula. But the words that remain are longer on average, which raises the second part.

In "The team completed the report," the three-syllable word "completed" now makes up a bigger share of a five-word sentence. The syllable average goes up, and the grade goes up with it.

This effect is strongest in one-sentence examples. Across a full page, the two parts tend to cancel out.

So why use active voice?

Because it helps readers, even though the score does not show it. The CDC's plain language guidance tells writers to use the active voice. The SEC's Plain English Handbook says the same, with one exception: the passive "may make sense when the person or thing performing the action is of secondary importance."

Active voice answers the question "who does what?" A formula has no way to measure that.

What to do

• Edit for voice to help the reader, not to move the number.
• Use the score for what it measures. If the grade is too high, look for long sentences and long words. Our guide on how to lower sentence length covers the first, and the list of shorter substitutes covers the second.
• Compare whole passages, not single sentences. A one-sentence score swings on a single word.

You can test your own before-and-after text with the draft comparison tool.

How we checked

We scored each sentence in this site's calculator and report the Flesch-Kincaid grade it gave. We did not run a study, and three pairs prove nothing about writing in general. They show how the formula behaves.