The Question Every Writer Faces

Should it be "7 people" or "seven people"? "100 dollars" or "one hundred dollars"? "3rd floor" or "third floor"? The rules around writing numbers are surprisingly inconsistent across style guides, but a few core principles will steer you right in almost every situation.

The Basic Rule

Most style guides agree on this: spell out numbers one through nine, and use digits for 10 and above. This is the AP Stylebook standard and the most widely followed convention in general writing.

  • "She has three cats and 12 houseplants."
  • "The team has six members but needs at least 15."

The Chicago Manual of Style prefers spelling out numbers one through ninety-nine, which is more common in book publishing. Know which guide your audience expects, and follow it consistently.

Important Exceptions

Always use digits for: ages when used as identifiers (a 6-year-old), dates (March 5), percentages (8 percent or 8%), addresses (7 Oak Lane), times (3 p.m.), and scores or statistics (a 4-3 victory).

Always spell out: numbers that begin a sentence. "Twelve people attended" is correct. "12 people attended" at the start of a sentence is not. If spelling out the number feels awkward ("Three hundred and forty-seven people attended"), restructure the sentence: "A total of 347 people attended."

Be consistent within a category. If one sentence says "we interviewed 15 candidates," do not say "we hired six" in the next sentence. When numbers in the same category appear near each other, use the same format for all of them: "We interviewed 15 candidates and hired 6."

Money, Measurements, and Large Numbers

For money, use digits with the currency symbol: $5, $1,200, $3.5 million. Spell out casual references: "it cost a few hundred dollars."

For large round numbers, a hybrid approach works best: 5 million, 12 billion, 300,000. Avoid writing out extremely large numbers in words, "three hundred and forty-seven thousand, two hundred and twelve" is painful to read.

The Practical Takeaway

When in doubt, ask yourself which format is easier to read. Numbers exist to convey quantity, and the format should serve comprehension. If digits are clearer, use digits. If words flow better in the sentence, spell it out. Consistency and readability matter more than rigid rule-following.