You have been told, probably by more than one teacher, to cut passive voice. That advice is mostly right. But like most absolute rules about prose, it falls apart the moment you look at how good writing actually behaves.

Passive voice is a tool. It has specific jobs it does well and specific jobs it does badly. The percentage of passive constructions in a piece is one of the cleanest signals you have about whether you are using it on purpose.

What passive voice is, in one sentence

A sentence is passive when the grammatical subject receives the action instead of performing it. “The letter was sent by Anna” is passive. “Anna sent the letter” is active. The action is the same. The spotlight is different.

When passive voice is the right choice

When you genuinely do not know, or do not want to reveal, who did the thing. “ The window was broken sometime before dawn.” The mystery is the point.
When the receiver of the action matters more than the actor. “She was hit by a car” keeps the focus on her, not the car.
When you want distance, bureaucracy, or avoidance as a deliberate effect. Used sparingly, this is powerful.
When the actor is obvious or generic. “The bill was passed” is fine if the reader knows legislatures pass bills.

When passive voice drains your prose

Most of the time, passive voice costs you two things: momentum and clarity. The sentence gets longer, the verb gets weaker, and the actor disappears behind a wall of helping verbs. Readers slow down. They may not know why, but the pages start to feel like a slog.

In fiction, passive voice is especially punishing in scenes of action and conflict. “The sword was drawn by the knight” lands with a thud. “The knight drew his sword” lands like a hammer.

Rough targets for passive voice percentage

Commercial fiction and tight prose: under 5 percent.
Literary fiction and personal essay: 5 to 10 percent is common and often intentional.
Academic or formal nonfiction: 10 to 20 percent is normal. The conventions of the field call for more distance.
Over 20 percent in narrative writing: something is wrong. You are probably hiding your actors.

A practice loop for cutting passive voice

Pick a page from a current draft.
Paste it into Prose Grade. Note the passive voice percent.
Go back to the draft and find every passive construction. Ask two questions about each one. Who is doing the action? Do I want the reader to know?
If the answer to both is yes, rewrite it active. If either answer is no, leave it. You have found a passive construction that is doing a job.
Re-grade. The number should drop by at least half if you were sloppy before.

The tool is not perfect

Passive voice detection is hard. The Prose Grade tool uses a regex that catches roughly ninety percent of constructions reliably. It will miss some edge cases and occasionally flag things that are not truly passive. That is fine. The percentage is directional, not exact, and directional is enough to catch a passive voice habit before it becomes a rut.

When you want this to track automatically across every draft you write, sign up free. Your passive voice percent will sit next to your other craft metrics so you can see the trend, not just a single number.