Dear Style Master: Why do I have to spell out numbers at the beginning of sentences?
– Numerals Rule!

Dear Ruler: Honestly, I don’t know why. I have searched high and low for the reason that the rule in all style guides is to use words rather than numerals to start sentences. My guess is that this rule has something to do with readability.

As with any rule, however, there are exceptions. Some style guides say you can begin a
sentence with a calendar year (“2013 was a tumultuous year for our family”) or with the name of an organization that begins with a number (3M). Headlines in news and marketing copy
also tend to use numerals rather than words to represent numbers. Using numerals at the
beginning of a sentence for emphasis, especially if they are treated graphically, makes sense to me. For example:

97% of our customers give us positive ratings for customer service!

In fact, a lot of marketing documents use numerals all the time, because they stand out and make readers take note.