Large Numbers in French
Thousands, Millions, Billions Explained

The Three Rules That Govern Everything

Rule 1: digit grouping with thin space. French uses a thin space (or non-breaking space) between groups of three digits in the integer part of any number greater than 9999. So 10 000, 100 000, 1 000 000, 1 000 000 000. Numbers from 0 to 9999 are written without grouping (1234 not 1 234, although the spaced form is also acceptable for consistency). The comma is the decimal separator: 3,14 for pi, 1 234 567,89 for one million two hundred thirty-four thousand five hundred sixty-seven and eighty-nine hundredths. This convention is documented in the BIPM SI brochure and is the standard for Légifrance, the Imprimerie nationale, and major French press.

Rule 2: noun vs determiner. French number words split into two grammatical classes. Determiners (un, deux, vingt, cent, mille) attach directly to the noun they count, with no preposition: vingt euros, cent mille personnes. Quantitative nouns (million, milliard, billion, douzaine, dizaine, centaine) require de before the counted noun: un million d’euros, deux milliards d’années. Knowing which class a word belongs to determines whether de is needed.

Rule 3: conditional plural-s on cent and vingt. Cent and vingt take a plural-s when (a) they are multiplied by another number AND (b) nothing else follows in the count. So deux cents (200), quatre-vingts (80) but deux cent un (201), quatre-vingt-trois (83). Quantitative nouns (millions, milliards) pluralise unconditionally whenever the count is greater than one. Mille is the exception: it never pluralises in any context.

The Full Ladder: 10 000 to 1 000 000 000 000 000

Thousands: 10 000 to 999 999

The thousands range is the simplest. Mille is invariable, so the plural-s never appears regardless of how many thousands you have. Deux mille (2,000), cinq mille (5,000), dix mille (10,000), cent mille (100,000), cinq cent mille (500,000). The compound forms concatenate without the “et” connector: cinq mille deux cents (5,200), dix mille cinq cent vingt-trois (10,523). The only place “et” appears in this range is the units position of the round tens: cinq mille trois cent vingt et un (5,321), cinq mille trois cent soixante et onze (5,371).

Cent behaves conditionally. Deux cent mille (200,000) drops the s on cent because mille follows. Trois cent cinquante mille (350,000), cinq cent mille (500,000), neuf cent mille (900,000). All take cent without the s. The single case where cent keeps its s in the thousands range is when cent is the very last counting word: deux mille deux cents (2,200) ends with the multiplied cent and nothing follows, so the s appears.

For everyday contexts, the thousands form is the working unit of pricing (most apartments, cars, computers, salaries fall here), of population for towns and small cities, and of distances. Mille kilomètres (1,000 km) is the working unit of road-distance journalism in France. Cent mille euros (€100k) is roughly the threshold for “serious money” in everyday usage. Cinq cent mille euros sits at the upper end of typical French middle-class home prices outside Paris and the Côte d’Azur.

Millions: 1 000 000 to 999 999 999

The millions range introduces the noun-class behaviour. Million takes the article (un, une if feminine context, le, les for definite forms), pluralises every time the count is greater than one (deux millions, cent millions), and requires de before any directly-following counted noun. The result: at the millions scale, every quantity expressed with a noun has the de-preposition between the number and the noun. Un million d’euros, deux millions d’habitants, cinq millions de tonnes.

Compound millions concatenate without “et”. Un million cinq cent mille (1,500,000), deux millions trois cent mille (2,300,000), cent millions cinq cent mille (100,500,000). The de appears only at the boundary with a counted noun, not inside the count itself. So un million cinq cent mille euros has zero de inside the count; un million d’euros has de because the count ends at million directly.

Common contexts at this scale: city populations (Paris compte deux millions d’habitants intra-muros), national budgets at the line-item level, mid-cap company revenues, asteroid distances and physical sizes, geological time intervals (millions of years), and the box-office tally of major French film releases. See the dedicated un million and cent millions pages for in-depth coverage.

Milliards and Beyond: The Long Scale

At 10^9 (one thousand million), the long-scale convention takes over. Un milliard = English “one billion”. The French billion exists but means 10^12 (English “trillion”), which is the famous false-friend trap. The full long-scale ladder: million (10^6), milliard (10^9), billion (10^12), billiard (10^15), trillion (10^18), trilliard (10^21).

All long-scale forms behave as nouns (article, plural-s, de-preposition before counted nouns). Deux milliards, cinq billions, dix billiards. In practice, French speakers and writers very rarely use billion or higher; the ambiguity with English “billion” has pushed continental French toward mille milliards (a thousand billions = English trillion) for clarity. National debt of large economies is conventionally given as milliers de milliards in popular reporting.

For very large quantities (population of stars in galaxies, atom counts, molecule counts, geological history time), French defaults to scientific notation (10^9, 10^12) and SI prefixes (giga, tera, peta, exa). The SI prefixes are language-independent and avoid the long-scale-vs-short-scale confusion entirely. See the dedicated un milliard page for the full long-scale-vs-short-scale comparison and SI prefix table.

Worked Compound Examples

Frequently Asked Questions