Vietnamese Numbers: The Exceptions That'll Trip You Up (And Why 15 Is Weird)

Look, if you're learning Vietnamese and someone told you the number system is "logical and easy," they weren't lying—but they also weren't telling you the whole truth.

Yeah, Vietnamese numbers follow a pattern. You learn 1-10, then everything builds from there. Simple, right? Except there are these random exceptions that'll make you second-guess yourself every time you try to say "fifteen" or count past twenty. And don't even get me started on why the number 4 makes Vietnamese people uncomfortable.

Here's what you actually need to know about Vietnamese numbers—the stuff that matters, the parts that are genuinely tricky, and the cultural quirks that'll help you understand why your Vietnamese friend insists on a phone number ending in 8.

The Basics (But Tones Matter Way More Than You Think)

Vietnamese numbers from 0-10 are straightforward:

The pattern works like English but simpler. Eleven is just "ten-one" (mười một), twelve is "ten-two" (mười hai). No weird "eleven" and "twelve" to memorize.

But here's the thing: if you get the tone wrong, you're saying a completely different word. "Năm" with the wrong tone could mean "to lie down" or "to hold" instead of "five." Vietnamese has six tones, and they're not suggestions—they change the entire meaning of what you're saying.

We actually wrote a whole post about Vietnamese tones if you want the full breakdown. The short version: you can't half-ass the tones. Master them early or you'll be asking for "ten years" when you meant to say "fifteen."

The Weird Exception: Why 15 Is Special

Okay, so you'd think fifteen would be "mười năm" (ten-five), right?

Wrong. It's "mười lăm."

Why? Because "mười năm" means "ten years." Vietnamese people got tired of the confusion, so they just... changed it. Fifteen uses "lăm" instead of "năm" to avoid this mess.

This is the only exception in the 11-19 range. Sixteen is normal (mười sáu), seventeen is normal (mười bảy)—just fifteen is weird.

And it gets weirder. That "lăm" thing? It happens every time 5 is in the ones place after 10. So 25 is "hai mươi lăm," 35 is "ba mươi lăm," all the way up to 95.

Oh, and speaking of which...

The Changes You Don't See Coming: Mười → Mươi

Once you hit 20, "mười" (ten) becomes "mươi" in compound numbers. So:

It's a pronunciation thing to keep everything clear. Fine, whatever. You get used to it.

But then there's this: the number 1 changes too when it's in the ones place. After 20, "một" becomes "mốt":

And remember that "lăm" exception for 5? Yeah, that applies here too:

So you've got "một" → "mốt" and "năm" → "lăm" happening in the ones place, but only after 10. This is the kind of stuff that's easy to explain but annoying to remember when you're actually trying to count in conversation.

The Zero Problem: Lẻ vs. Linh

When you've got a number like 103 or 205—where there's a zero in the tens place—you need to stick in a word to show that gap exists.

In the South, they use "lẻ." In the North, they use "linh" (borrowed from Chinese).

So 103 is:

Both mean the same thing. Which one you use depends on where you are or who taught you. Most learning resources default to Northern Vietnamese since that's the "standard" dialect, but honestly, both work.

The Cultural Stuff: Lucky and Unlucky Numbers

Vietnamese people care a lot about certain numbers. Not in a superstitious-but-secretly-don't-believe-it way—in a will-actually-pay-more-for-a-phone-number-with-8s way.

Number 8 is the big one. It sounds like the word for prosperity, so everyone wants it. License plates with 8s? More expensive. Business names? Loaded with 8s. Phone numbers? You get the idea.

Number 6 is also popular—it's associated with smooth progress and good fortune.

Number 4, though? That's the one people avoid. It sounds like "tử" (death), so buildings skip the 4th floor, addresses avoid it, and nobody's getting a phone number ending in 4 if they can help it. Floor 13 and 14 get replaced too (12A, 12B instead).

Number 9 represents longevity and eternity. That's why you see couples giving 99 or 999 roses—it's supposed to symbolize eternal love.

This isn't just trivia. If you're living in Vietnam, you'll notice it everywhere—from how people choose phone numbers to the amounts given in red envelopes during Tết (Lunar New Year). Understanding this helps you get why someone might insist on a specific number or avoid another one entirely.

Regional Differences (They Exist, But Don't Stress)

Vietnamese has three main dialects: Northern (Hanoi), Central (Huế/Da Nang), and Southern (Saigon). The number system is the same across all of them, but pronunciation changes.

The Northern dialect has all six tones clearly pronounced. The Southern dialect merges two of them, so it has five. Central Vietnamese is... well, it's the hardest to understand for everyone, including other Vietnamese people.

For numbers specifically, the main difference is that lẻ/linh thing we already mentioned. If you're learning Northern Vietnamese, you'll use "linh." If you're learning Southern, you'll use "lẻ." Both are correct.

The writing is always the same, though. So whether someone's from Hanoi or Saigon, they'll write numbers identically—it's just the pronunciation that shifts.

What About Bigger Numbers?

Vietnamese uses a thousands-based system like English (not the ten-thousands system that Chinese and Japanese use). So:

One weird thing: Vietnam uses the opposite punctuation from English when writing numbers. The period is the thousands separator, and the comma is the decimal point.

So if you see 500.000 on a price tag? That's five hundred thousand, not five hundred. And 37.500,75 would be thirty-seven thousand five hundred point seventy-five.

This trips people up constantly, especially when dealing with Vietnamese currency (the dong). Ten million dong sounds like a fortune, but it's only about $400 USD. The currency has so many zeros that prices look absurd if you're not used to it.

The Honest Truth About Learning Vietnamese Numbers

The pattern is logical. Once you get the exceptions down—15, the mốt/lăm changes, the lẻ/linh insertion—it's actually pretty easy to count to any number.

The hard part is the tones. You can know every rule perfectly and still stumble because you said "một" with the wrong pitch. That's not something you fix by memorizing more rules—it's something you fix by hearing the language constantly and practicing pronunciation until it sticks.

And that's where most Vietnamese learning resources fall short. They'll teach you the number system, maybe give you some audio clips, but they won't put you in situations where you actually use numbers naturally. You end up knowing the rules but freezing when someone asks you how much something costs or what time it is.

If you want to actually get comfortable with Vietnamese numbers, you need to hear them in context—not just drilled in isolation. Migaku's browser extension lets you learn Vietnamese from real content like Netflix shows and YouTube videos, where people are using numbers naturally. You'll see prices, ages, dates, times—all with instant lookups and the option to save words to your spaced repetition deck.

The difference is that you're learning numbers the way Vietnamese people actually use them, not the way a textbook presents them. When you're watching a Vietnamese show and someone mentions "ba mươi lăm" (35) or "hai trăm ngàn" (two hundred thousand), you're building real comprehension instead of just memorizing rules.

You can try it free for 10 days and see if learning from actual Vietnamese content works better than grinding through number drills. The extension handles the lookups, the flashcards sync across devices, and you're learning from stuff that's actually interesting instead of textbook exercises.