Grammar and mechanics · hard · v4.6.1

GRM-05

Use numerals for numbers in body copy. Spell out a number only when it begins a sentence.

Pass example

You have 3 invitations and 12 unread messages.

Fail example

You have three invitations and twelve unread messages.

Relevant content types

Weighted in these moments

This standard behaves differently depending on the reader's moment. Moment-aware evaluation picks one of these adjustments when the moment matches.

  • decision_point — emphasize
    Use numerals in pricing and comparisons for quick scanning.

Example pairs

Concrete before/after pairs observed in public style guides, each with inline attribution. See /sources for the full source list and licensing.

  • decision_point · short_ui_copyCC-BY-NC-ND-4.0

    Not this. Save up to thirty percent when you upgrade.

    But this. Save up to 30% when you upgrade.

    Mailchimp + Chicago: use numerals for data (prices, percentages) so readers can scan. Spell out non-data numbers. — Mailchimp · Grammar and mechanics — Numbers

Sources

Style guides that shaped this standard. Each is listed on /sources with its license and opt-out path.

  • Mailchimp
  • Microsoft Writing Style Guide
  • Chicago Manual of Style

Version history

  1. v4.6.1 · 2026-04-23

    Per-standard version tracking introduced. Every standard starts at the library version current at introduction; bump per-standard when the rule text, examples, or content_type_notes change.

Related standards

Other standards in the Grammar and mechanics category.

  • GRM-01 — Use the serial comma (Oxford comma) in lists of three or more items.
  • GRM-02 — Spell out abbreviations and acronyms on first use in body copy and help content. Use the short form for subsequent mentions. Universally understood abbreviations (FAQ, URL, ZIP, LLC, IRS) and regulated accessibility terms (TTY) do not require expansion in any context. Internal or organization-specific abbreviations should always be expanded on a public-facing page. If the surrounding copy acknowledges the reader may not know a term, expand it.
  • GRM-03 — Use exclamation points sparingly. Never use more than one at a time, and never in error messages or alerts.
  • GRM-04 — Don't use ampersands in body copy unless they are part of a brand name. Ampersands are acceptable in headings, navigation labels, footer links, and other space-constrained UI elements where '&' is a conventional shorthand.
  • GRM-06 — Hyphenate number-unit compound modifiers before nouns. The unit takes singular form when hyphenated.

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