Need to shorten “million” in financial, business, or technical writing? Use M (uppercase). Stuck in a headline or tight space? AP style still says M. Everywhere else, spell it out. Just don’t confuse this with MM—that’s for Roman numerals or dusty old accounting books.
What’s the deal with “M” and “MM”?
Here’s why people get tripped up: both abbreviations come from Latin roots, but only M is the standard in 2026 financial and business writing. MM (short for “mille milia,” or thousand-thousand) still shows up in Roman numeral contexts or some legacy accounting systems. Outside those spots? It’s not the right modern choice.
How do I pick the right abbreviation?
- Pick your format
- In regular paragraphs or formal reports: spell out “million.”
- In headlines or tables where space is tight: go with M.
- If you’re working with old documents (think SEC filings from the '90s), check whether MM is required. If not, switch to M.
- Match your style guide
- AP Stylebook (2026 edition): “Use M for million in headlines; spell out in body copy.”
- Chicago Manual of Style (18th ed., 2024 update): “Abbreviate million as M in tables and lists; otherwise spell out.”
- Format your numbers
- Numbers under 1,000,000? Use digits without abbreviations (e.g., 450,000).
- Numbers over 1,000,000? Reserve M for tables or headers. In sentences, spell it out (e.g., 2.5 million, not 2.5M).
- Update old MM habits
- Open the document in Word or Google Docs.
- Hit Ctrl+H (Windows) or Cmd+Shift+H (Mac) to open Find & Replace.
- Search for: \$(\d+)\s*MM (turn on regex mode).
- Swap it for: $1M.
Still running into issues?
- Check who’s reading it: If regulators or investors expect MM, double-check the latest style sheet. Otherwise, switch to M to stay current with 2026 standards.
- Try an Excel fix: In Excel 365 (as of 2026), go to Data ▸ Get Data ▸ From Other Sources ▸ Blank Query, then paste in
=TEXT(A1,"0")&"M"to auto-format your cells. - Set up a CMS check: If you run a content management system, add a rule that flags any MM (Roman numerals excepted) and nudges you toward M instead.
How can I keep this from happening again?
- Overhaul your style guide to require M for million everywhere except headlines, and ban MM outside Roman numeral sections.
- Teach your team to run the Find & Replace trick above whenever they pull in old files.
- In dashboards, lock down a data-validation rule: if a column header says “million,” the cells must show either the full word or M—no MM allowed.
