A or An Before a Number? An 8, an 11, an 18, an 80, but a 7

Use "an" before a number when you say it aloud with a vowel sound, so it is "an 8," "an 11," "an 18," and "an 80%." Use "a" before every other number from 1 to 100, such as "a 7," "a 12," or "a 1:1," because the first sound is a consonant.

The rule is the same one you use for words. It is about sound, not spelling, and a digit is just a word you have not written out yet.

1. Why the digit does not matter

Both major dictionaries say the choice depends on what you hear. Merriam-Webster states that the deciding factor is the sound that begins the next word, "rather than the letter which does." Cambridge says to use "a" before a consonant sound and "an" before a vowel sound, and it warns that some words that begin with a vowel letter have a consonant sound, such as "a one-year-old child."

A numeral works the same way. The digit "8" is not a vowel or a consonant on the page. What matters is that you say "eight," which starts with a vowel sound, so you write "an 8." Stony Brook's style guide gives a numeral example of its own: "an 1890s celebration," since 1890s is read "eighteen nineties."

2. Which numbers take "an"

Spoken forms of 1 to 100, sorted by their first sound, give this result:

That is 1 + 1 + 1 + 10 = 13 numbers out of 100 that take "an." The other 87 take "a," including every number that starts with a consonant sound when spoken: "a 7," "a 12," "a 20," "a 30%," "a 99% score."

Two cases confuse people:

• The number 1 itself. "1" is "one," which begins with a "w" sound, so it takes "a." Merriam-Webster uses exactly this kind of example, "a one hundred dollar bill," and Cambridge gives "a one-year-old child." For a numeral, that means "a 1:1 meeting," "a 100-page report," and "a 10% increase" (ten).
• Numbers that start with the digit 1 but are not "one." The digit 1 begins 11 and 18, yet you say "eleven" and "eighteen," which start with vowel sounds, so it is "an 11" and "an 18." But 12 is "twelve," which starts with a "t" sound, so it is "a 12."

3. Larger numbers follow the same rule

Because the rule is about the first spoken syllable, it carries into larger figures:

• 800, 8,000 and 8 million: "an 800-word limit," "an 8,000-seat arena."
• 80,000 and 11,000: "an 80,000-person event," "an 11,000-word draft."
• 700 or 7,000: "a 700-word limit" (seven starts with "s").

If a number is pronounced in more than one way, choose the article for the way you will actually say it. Merriam-Webster quotes its usage dictionary on a similar case, "historic," which can be said either way: "You choose the article that best suits your own pronunciation." Where the reading is unclear to a reader, say a year-like figure such as 1100 could be read "eleven hundred" or "one thousand one hundred," so rewriting the sentence is cleaner than defending the article.

4. Percentages, currency and time

Symbols are read as words, so look at the first number you say:

• Percentages: "an 8% rise" (eight), "a 9% rise" (nine), "an 80% discount" (eighty), "a 70% discount" (seventy).
• Currency: "an $8 fee" (eight dollars) and "an $80 fee," but "a $5 fee" and "a $50 fee."
• Time: "an 8 a.m. call" and "an 11:30 start," but "a 9 a.m. call" and "a 4 p.m. deadline."
• Ratios and scores: "an 8-to-1 ratio," "a 3-to-1 ratio."

Notice the dollar sign case. You write "$8" but say "eight dollars," so the article follows the spoken number, not the symbol.

5. Work-email examples

Stony Brook's guide applies the same sound rule to abbreviations: it lists "an NBA record" because NBA sounds as if it begins with the letter "e." The same habit applies to initialisms; see the guide to when to use a, an, and the in work emails.

6. A quick check before you send

1. Say the number out loud as you would on a call.
2. Listen to the very first sound. Vowel sound: "an." Consonant sound: "a."
3. Ignore the digit you see and any symbol such as %, $ or a colon.
4. If the number could be read two ways, rewrite the phrase instead.

7. Key takeaways

• Use "an" before numbers spoken with a vowel sound: 8, 11, 18, and 80 to 89 (13 of the first 100 numbers).
• Use "a" before the other 87, including 1 ("a 1:1"), 7, 12 and 70.
• The sound rule from the dictionaries applies to digits, percentages, currency and times.
• Read the figure aloud to decide, and rewrite the sentence if two readings are possible.