Any fraction spelled out — including mixed numbers, and the two denominators that refuse to follow the rule.
Type a fraction — 3/4, or 1 1/2 for a mixed number — and read it in words.
Decimal
Simplified
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01 · the rule
The numerator is counted normally and the denominator is named with its ordinal: two thirds, five eighths, seven twelfths.
The denominator also takes an "s" once the numerator passes one — one third, but two thirds. The logic is that you are counting parts: two of the things called thirds. That single rule covers nearly every fraction in English.
Nearly every one, because two denominators ignore it entirely, and they happen to be the two you use most.
Worth noting before the exceptions: the ordinal in a fraction is doing a different job from the ordinal in a ranking. "Third" in "the third runner" marks a position, while "third" in "two thirds" names a size of part. English reuses the same word for both, which is convenient and occasionally confusing, and is the reason a fraction can be pluralised at all. You cannot have two third runners, but you can certainly have two thirds of a cake.
02 · the exceptions
1/2 — never "second"
one half · three halves
English kept an old word instead of using the ordinal, and it pluralises irregularly: halves, not halfs. It is the only fraction word that does.
1/4 — two valid names
three quarters · three fourths
"Quarter" is the everyday word; "fourth" is common in American arithmetic. Both are correct, and the converter returns each.
Every other denominator behaves: fifths, sixths, sevenths, eighths, and so on up. Third is worth a note only because it looks irregular and is not — it is simply the ordinal of three, which happens to be short.
The choice between quarter and fourth is worth a moment because it is not free. "A quarter" carries meanings that "a fourth" does not: a quarter of an hour, a quarter past three, the last quarter of the year, quarters as accommodation. In those the word has stopped being a fraction and become a unit in its own right, which is why nobody says "a fourth past three". Where the sentence is genuinely arithmetic — dividing something into four and taking three — both work, and American teaching materials tend to prefer fourths for the consistency with fifths and sixths.
03 · worked fractions
All from the converter above, mixed numbers included.
| Fraction | In words | Decimal |
|---|---|---|
| 1/2 | one half | 0.5 |
| 1/3 | one third | 0.333… |
| 2/3 | two thirds | 0.666… |
| 1/4 | one quarter | 0.25 |
| 3/4 | three quarters | 0.75 |
| 1/5 | one fifth | 0.2 |
| 5/8 | five eighths | 0.625 |
| 3/10 | three tenths | 0.3 |
| 7/12 | seven twelfths | 0.583… |
| 1 1/2 | one and a half | 1.5 |
| 2 1/4 | two and a quarter | 2.25 |
| 3 1/8 | three and an eighth | 3.125 |
04 · mixed numbers
A mixed number in English takes an article rather than the numeral: one and a half, two and a quarter, three and an eighth. "One and one half" is arithmetically fine and nobody says it out loud.
The article follows the ordinary rule — "an" before a vowel sound, so "an eighth" but "a half". Once the numerator passes one, the article gives way to the number: one and three quarters.
This is one of those rules nobody is taught and everybody follows. It only becomes visible when a machine writes the phrase and gets it slightly wrong.
05 · which form
The same quantity can be written three ways — three quarters, 0.75, 75 % — and they are not interchangeable. Each one tells the reader something about where the number came from.
A fraction says the quantity is exact and came from dividing something: three quarters of the budget, two thirds of the members. It is also the only form that can hold a repeating value precisely — one third is exact where 0.333 is rounded.
A decimal says the number was measured or calculated, and it carries an implied precision: 0.75 suggests two significant places, 0.750 suggests three. A percentage says the number is a proportion of something, and invites comparison with other proportions.
In practice the fraction wins when the denominator is small and familiar — halves, thirds, quarters, eighths — and loses as it grows. "Seventeen fortieths" is correct and nobody would write it; 0.425 says the same thing without making the reader do arithmetic. The converter above shows the decimal beside the words for exactly this reason: it lets you see whether the fraction is the clearer form before you commit to it.
One place the fraction is not optional is cooking and construction, where measurements come in halves, quarters and eighths because that is how the tools are divided. A tape measure has no 0.375 mark on it, but it has a three-eighths line.
06 · mistakes
— one second (for 1/2)
+ one half
Two is the one denominator that never uses its ordinal. A "second" is a unit of time, and the fraction is a half.
— two third
+ two thirds
The denominator takes an "s" whenever the numerator is more than one. It is a plural of the thing being counted: two of the thirds.
— three halfs
+ three halves
Half pluralises irregularly, like leaf and knife. This is the only fraction word that does.
— one and one half
+ one and a half
Mixed numbers take the article, not the numeral, in ordinary English. "One and one half" is not wrong in arithmetic, but nobody says it.
— two fourths
+ one half
Not incorrect, but unreduced. Fractions are normally simplified before being written out, which is why the converter reduces first.
07 · questions
Q01
Numerator as a cardinal, denominator as an ordinal: one third, three fifths, seven twelfths. The denominator takes an "s" when the numerator is more than one. Two exceptions break the pattern — half for 2 and quarter for 4.
Q02
Both are correct. "Quarter" is the everyday word — a quarter of an hour, three quarters of the way — while "fourth" is common in American arithmetic and teaching: three fourths. The converter shows both, because they belong to different registers rather than one being an error.
Q03
History rather than logic. English took "half" from Old English and never replaced it with the ordinal, unlike third, fourth and the rest. Its plural is irregular too: three halves, not three halfs.
Q04
Whenever the numerator is more than one: one third but two thirds, one eighth but five eighths. The reasoning is that you are counting the parts, so the part becomes plural.
Q05
Whole number, "and", then the fraction with an article: one and a half, two and a quarter, three and an eighth. The article follows the usual rule — "an" before a vowel sound. Above a numerator of one it becomes a numeral: one and three quarters.
Q06
Normally yes. "Two fourths" is understandable but reads as unfinished work; "one half" is what a reader expects. The converter reduces automatically and tells you when it did, so you can see what the original was.
Q07
The same way, with the ordinal: one hundredth, three thousandths, one millionth. Past a certain size it stops being idiomatic and people switch to decimals or percentages — "three thousandths" is usually clearer written as 0.003 or 0.3%.
Q08
The same words, but the unit usually comes first or last depending on the trade: "three eighths of an inch" in full, "three eighths" alone once the unit is understood. In cooking, quantities are read the same way — half a cup, three quarters of a teaspoon — and the article slips in front of the unit rather than the fraction.
Q09
It can, and it is called a complex fraction, but English has no comfortable way to say one aloud. A half over a third is read as "a half divided by a third" rather than named as a single quantity, which is a good sign it should be simplified before anyone has to read it.
Q10
The structure is similar but the vocabulary is not. Spanish uses partitive forms that diverge from the ordinals past ten — onceavo rather than undécimo — and both languages agree in gender. Each has a page on this site with its own rules.
That covers everything except half and quarter, which you already know by ear. The converter simplifies first and gives the decimal alongside.