The French Numbers 'Nonsense': Why 70 is 60+10 and 80 is 4x20?

If you've ever been learning French and felt like throwing your notebook across the room when you got to the number 70, you are not alone.

A recent Reddit post perfectly captured this frustration, calling the numbers 70-99 "absolute nonsense" and joking that whoever invented them "deserved the guillotine."

It’s a rite of passage for every French learner. You cruise through un, deux, trois, master the teens, and even feel confident with soixante (60).

Then, you hit a wall.

• 70 isn't a unique word. It's soixante-dix (sixty-ten).
• 80 is where things get truly wild: quatre-vingts (four-twenties).
• And 90 is a full-on math equation: quatre-vingt-dix (four-twenty-ten).

Why? Why would a language do this?

It's not nonsense, it's history. And understanding it makes these numbers much easier to remember.

The Surprising History: Why is it 'Four-Twenties'?

The simple answer is that the French counting system is a mix of two different systems:

1. Decimal (Base-10): This is what we're used to. It's simple, logical, and based on the number 10. This is what French uses for trente (30), quarante (40), cinquante (50), and soixante (60).
2. Vigesimal (Base-20): This is an ancient system used by cultures like the Celts (Gauls) and Vikings, who counted by 20s instead of 10s.

Modern French is a linguistic fossil. It uses the logical base-10 system for most numbers, but it keeps an echo of the old base-20 system for 80 (quatre-vingts or "four-twenties"). This old system was once used for all numbers, but it only "stuck" for 80.

Because 80 became "four-twenties," the numbers on either side had to adapt. 70 became the "sixty-ten" that leads up to 80, and 90 became the "four-twenty-ten" that comes after it.

It's a perfect example of the real-world conversational nuance we focus on in our French course.

But Wait... What About 'Septante'?

Here's the most ironic part: the "simpler" numbers the Reddit poster wished for actually exist.

While standard French (the kind taught in Paris and in most international schools) uses the complicated forms, other French-speaking regions held on to the logical, base-10 versions.

• Belgium: People in Belgium say septante (70) and nonante (90). However, they generally still use quatre-vingts (80).
• Switzerland (and some parts of Canada): The Swiss go all the way. They use septante (70), huitante (80), and nonante (90).

So, if you ever hear a French speaker use septante, they are likely from Belgium or Switzerland. It's perfectly correct, just not the standard in France.

How to Actually Learn French Numbers 70-99

Okay, history is interesting, but you still need to pass your test and order quatre-vingt-deux (82) croissants. How do you remember these?

The trick is to stop doing math in your head.

Don't think of quatre-vingt-dix as "4 x 20 + 10." You must train your brain to see that combination of sounds as a single unit that simply means "90."

Here are three practical tips:

1. Drill with Flashcards: Make digital or physical flashcards. On one side, write "91." On the other, write quatre-vingt-onze. Drill them until the connection is automatic.
2. Practice with Phone Numbers: This is the single best trick. Take a friend's phone number and say it aloud in French, two digits at a time. "06 70 82 95 13" becomes "zéro six, soixante-dix, quatre-vingt-deux, quatre-vingt-quinze, treize."
3. Listen and Repeat: Find videos on YouTube of native speakers counting. Listen to the rhythm. Quatre-vingt-dix-neuf (99) has a specific flow. Mimic it.

Your Cheat Sheet for 70-99

It's Not Nonsense, It's a Quirk

So, are the numbers "nonsense"? From a modern, logical perspective, maybe. But they're also a fascinating piece of living history.

Every time you say quatre-vingts, you're using the same counting system a Celtic warrior might have used 2,000 years ago. It’s a quirk, not a flaw. And once you learn the pattern, you'll feel even more accomplished.

What about you? What's your trick for remembering French numbers? Do you prefer the logic of septante or the history of soixante-dix?

Wanna learn more? let’s go to our French course.