Fractions

Introduction

We use fractions (los números fraccionarios or fracciones) to refer to parts of a whole. We use fractions in mathematics as well as in everyday contexts such as recipes (½ litro de agua).

How to write fractions in Spanish

Fraction Noun Adjective
1/2 mitad or medio medio, media
1/3 tercio tercera (parte)
1/4 cuarto cuarta (parte)
1/5 quinto quinta (parte)
1/6 sexto sexta (parte)
1/7 séptimo séptima (parte)
1/8 octavo octava (parte)
1/9 noveno novena (parte)
1/10 décimo or décima décima (parte)
1/11 onceavo or undécimo onceava or undécima (parte)
1/12 doceavo or duodécimo doceava or duodécima (parte)
1/13 treceavo treceava (parte)
1/14 catorceavo catorceava (parte)
1/20 veinteavo or vigésimo veinteava or vigésima(parte)
1/22 veintidosavo veintidosava or vigésimo segunda (parte)
1/30 treintavo or trigésimo treintava or trigésima (parte)
1/40 cuarentavo or cuadragésimo cuarentava or cuadragésima (parte)
1/50 cincuentavo or quincuagésimo cincuentuava or quincuagésima (parte)
1/55 cincuentaicincoavo cincuentaicincoava or quincuagésimo quinta (parte)
1/60 sesentavo or sexagésimo sesentava or sexagésima (parte)
1/70 setentavo or septuagésimo setentava or septuagésima (parte)
1/80 ochentavo or octogésimo ochentava or octogésima (parte)
1/90 noventavo or nonagésimo noventava or nonagésima (parte)
1/100 centésimo or centésima centésima (parte)
1/105 cientocincoavo cientociencoava (parte)
1/1.000 milésimo or milésima milésima (parte)
1/10.000 diezmilésimo or diezmilésima diezmilésima (parte)
1/100.000 cienmilésimo or cienmilésima cienmilésima (parte)
1/1.000.000 millonésimo or millonésima millonésima (parte)
1/2.000.000 dosmillonésimo or dosmillonésima dosmillonésima (parte)

Things to know about Spanish fractions

Spanish fractions are similar to English fractions: we read the numerator as a cardinal number and the denominator as an ordinal number. The denominator is plural if the numerator is higher than 1.

Examples:
1/4 → un cuarto
3/4 → tres cuartos

Exceptions

mitad or medio (½)

The word medio is used in the same way as an adjective. It agrees with the gender and number of the noun it describes.

Examples:
medio litro de aguahalf litre of water
media docena de huevoshalf dozen eggs

The word mitad is usually followed by the preposition de + noun.

Example:
la mitad de un préstamothe half of the loan
mitad de huevos (informal: it goes without saying that it’s a dozen)

Denominators from 3 to 10

Fractions whose denominators include the numbers 3 to 10 are expressed as ordinal numbers. If the number is more than 1, the denominator is plural.

Examples:
1/3 → un tercio
4/6 → cuatro sextos

Denominators from 11

From the number 11 denominators are read as cardinal numbers with the ending –avo(s).

Example:
1/11 → un onceavo

If the denominator is a cardinal number made up of two or more words, we write them as one word. The preposition y becomes an i. In the event that two vowels appear one after another, we only write one.

Examples:
9/99 → nueve noventainueveavos
1/30 → un treintavo (not: un treintaavo)
5/108 → cinco cientochoavos (not: cinco cientoochovaos)

For multiples of ten in the tens (20, 30, 40, …), we can also use ordinal numbers.

Example:
1/40 → un cuadragésimo o un cuarentavo

However, we don’t typically use the –avo ending as an adjective.

Examples:
una vigésima parte de la población (common)a twentieth of the population
una veinteava parte de la población (less common)

For multiples of ten in the hundreds, thousands, hundred thousands etc. we always use ordinal numbers.

Example:
1/20,000 → un veintemilésimo

Info

When using fractions in the hundreds, thousands, hundred thousands etc. as nouns, Spain uses the feminine form of the noun while some countries in Latin America also use the masculine form.

Examples:
la diferencia de una décima de milímetro (Spain)the difference of one tenth of a millimetre
la diferencia de un décimo de milímetro (Latin America)