Fractions and decimals trip up even confident writers. Is it "two-thirds" or "two thirds"? Do you write "0.5" as "zero point five" or "one-half"? Small choices like these change meaning, especially on cheques, invoices, and school assignments. Here is a clear set of rules you can use every time.
Fractions in words
Write simple fractions with a hyphen: one-half, two-thirds, three-quarters, five-eighths. The top number (numerator) is a cardinal number and the bottom number (denominator) is an ordinal number. So 3/4 becomes "three-quarters" and 7/10 becomes "seven-tenths". When a fraction is part of a sentence, the hyphen keeps it readable: "She ate two-thirds of the cake." Without the hyphen, the same words can read like a clumsy list of numbers.
Mixed numbers need "and"
A mixed number joins a whole number to a fraction with "and": 2 1/2 is "two and one-half", and 4 3/4 is "four and three-quarters". Never drop the "and" — "two one-half" reads like two separate quantities. On formal documents, this matters: a missing "and" can make a payment amount ambiguous, which is exactly why banks ask for amounts in words on cheques.
Decimals in words
Read decimals digit by digit after the point. 0.5 is "zero point five", 3.14 is "three point one four", and 12.75 is "twelve point seven five". Never say "point seventy-five" — each digit after the decimal point is spoken separately. The one exception is money: $12.75 is normally written "twelve dollars and seventy-five cents", not "twelve point seven five dollars".
Percentages in words
In formal writing, spell out "percent": "twenty-five percent", not "25%". The number itself follows the usual rules: whole numbers are spelled out ("forty percent"), while decimals keep the digit-by-digit rule ("two point five percent"). In business writing, digits with the % sign are fine, but a cheque or a legal letter should spell the amount out in full.
Common mistakes to avoid
First, mixing formats in one document: do not write "two-thirds" in one paragraph and "2/3" in the next. Pick one style and keep it. Second, forgetting the hyphen in fractions: "two thirds" without a hyphen is acceptable in some style guides, but the hyphenated form is clearer and never wrong. Third, writing "and" where it does not belong: in American usage, "one hundred and five" is often shortened to "one hundred five", but in fractions and mixed numbers the "and" is required. Consistency beats cleverness every time.
A quick practice set
Try these: 1/3, 5/8, 2 1/4, 0.25, 6.5, 33%. Answers: one-third, five-eighths, two and one-quarter, zero point two five, six point five, thirty-three percent. If you got them all, you have the rules down. For anything trickier — large amounts, ordinals, or cheque wording — a free numbers-to-words converter can double-check your work in seconds.
If you want a fast way to check any number, try the free converter at https://wordsfornumbers.com/ — type the number and it spells it out for you.
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