1 The rule in plain terms
The working rule is short: use the percent sign with a numeral. Write 4%, 12.5%, 0.8%, and 100%. Close the figure up to the sign with no space, because the sign is part of the number rather than a separate word. In a sentence, the figure and sign travel together: Sales climbed 6% in the period. Do not write six percent, 6 per cent, or 6 %.
The same logic applies in tables, charts, and headlines, where space is tight and the sign reads faster than the word. A headline that says Rates rise 3% is doing exactly what a headline should do. The spelled-out word percent belongs in casual or literary prose where no numeral appears, as in a small share of the proceeds, a few percent at most. When a figure is present, the sign wins.
One more distinction belongs in the same breath. A change from 10% to 12% is a rise of 2 percentage points, not a rise of 2%. The first describes the gap between two rates; the second describes a relative change. Keep those two ideas separate and most percentage confusion disappears before an editor ever sees the copy.
2 Why editors enforce it
Editors enforce the numeral-plus-sign form because it is compact, unambiguous, and consistent across a whole publication. A reader who sees 4% in one story and four percent in the next has to do a small amount of unnecessary work. Consistency removes that work. It also makes scanning easier: the eye catches the sign, registers a quantity, and moves on.
The rule earns its keep in data-heavy copy. When every percentage in a report looks the same, readers can compare figures without wondering whether the writer changed conventions mid-story. That matters in earnings summaries, health stories, sports recaps, and any piece where numbers carry the argument. A mixed style suggests the figures were assembled carelessly, even when they were not.
There is also a precision argument. The sign is a symbol with one meaning, while the word percent can drift into vague use, as in a percent of the total when the writer means a portion. Forcing the numeral keeps the writer honest about whether a real figure exists. If it does, the sign goes in. If it does not, the writer reaches for a phrase such as a small share or a fraction. That habit alone prevents a surprising number of soft, unfalsifiable claims from reaching print.
3 Where writers usually slip
The most common slip is the space: 6 % instead of 6%. Writers add it because the sign looks like a unit, and units often take a space. The percent sign does not. It is glued to the figure, and a stray space is one of the first things a copy desk fixes.
A close second is the hybrid form, as in seven% or 7 percent in the same paragraph as 7%. Mixing the two styles inside one piece is the error readers notice, even if they cannot name it. Pick the numeral-and-sign form and hold it throughout the story, including in quotations unless the speaker's exact words matter to the meaning.
The third slip is the percentage-point mix-up. A writer sees a rate move from 4% to 6% and calls it a 2% increase. It is a 2 percentage point increase, or a 50% relative increase, depending on what is being measured. Both statements can be true, but they say different things. The fix is to ask what changed: the rate itself or the distance between two rates. Name that clearly, and the arithmetic stays honest.
4 Applying the rule on deadline
On deadline, run a fast pass over every percentage in the copy. Check three things: the sign is present, the sign is closed up to the figure, and the figure is a numeral. That pass takes seconds and catches most errors. Read the sentence aloud if a percentage sits near another number, because the ear often hears a missing sign faster than the eye sees one.
Next, check the comparison language. If the copy compares two rates, decide whether the story is about the gap or the relative change, then use percentage points or percent accordingly. A sentence such as The rate fell 3 percentage points is clear. A sentence such as The rate fell 3% is also clear, but only if the writer means a relative drop. Do not leave the reader to guess which one is meant.
Finally, check ranges and series. Write 3% to 5%, not 3-5%, when the sign is needed for clarity, and repeat the sign in a series only when the numbers are far apart or the sentence would otherwise confuse. In tables, a single percent sign in the column heading can cover every figure below it. That is a legitimate space saver, not a style break, as long as the heading makes the unit plain.
5 Legitimate exceptions
The rule bends in a few predictable places. At the start of a sentence, spell out the word and the number: Fifty percent of respondents chose the first option. Starting a sentence with a numeral is awkward in most prose, and the spelled-out form reads better. The same treatment applies to a sentence that begins with a fraction or a vague quantity.
In direct quotations, keep the speaker's words when the wording itself is the point. If a source said the word percent, a quotation may retain it, though many desks silently convert to the sign for consistency. The safer practice is to use the sign in the quotation unless the exact phrasing matters, and to note any change only if the meaning shifts.
Casual and literary prose can spell out percent when no figure appears, as in a few percent of the total. Headlines, tables, and charts may drop the sign entirely when a column heading or a label supplies the unit. And in legal or formal documents that follow their own convention, the house rule yields to the governing style. Outside those cases, the numeral and the sign stay together.
6 A worked example from the copy desk
A draft sentence arrives reading: The program grew seven percent last year, and its share of the budget rose from 4 % to 6 %, a two percent gain. The desk makes four changes. It converts seven percent to 7%. It closes the space in 4 % and 6 %. It replaces the vague two percent gain with 2 percentage points, because the sentence compares two rates. The result reads: The program grew 7% last year, and its share of the budget rose from 4% to 6%, a gain of 2 percentage points.
Now consider a second sentence: Fifty percent of the sample reported the same result. Here the desk leaves the spelled-out form because the sentence opens with the figure. If the same idea appeared mid-sentence, it would become 50% of the sample. The position of the figure, not the size of the number, drives the choice.
A third case: a chart shows a column of rates under the heading Share of total (%). The desk leaves the individual figures bare, since the heading supplies the unit. That is the exception working as intended. The test in every case is whether a reader can tell what the figure measures without stopping to work it out. If yes, the copy is clean. If no, the sign or the label goes back in.
7 Quick reference and related rules
Use the sign with numerals: 5%, 12.5%, 0.4%. Close it up. Keep it consistent within a story. Spell out percent only at the start of a sentence, in casual prose with no figure, or when a quotation or governing style requires it. Use percentage points for the gap between two rates and percent for a relative change. Repeat the sign in a range when clarity demands it, and let a column heading carry the unit in tables.
Related rules travel with this one. Treat percent like a unit that belongs to the number, so it follows the same logic as dollar signs and degree symbols: no space, no spelled-out hybrid. In a series, decide whether the sign repeats based on distance and clarity, not habit. When a percentage appears in a headline, keep the numeral and the sign, and let the verb carry the change.
Finally, keep the arithmetic visible. A percentage is a claim about a base, and the base should be clear from the sentence or the surrounding copy. If a reader cannot tell what the percentage is a percentage of, the style is not the problem; the reporting is. Fix the base, then apply the sign, and the sentence will hold up under any editor's read.