Why does 1 sometimes read một and sometimes mốt?

A units digit of 1 reads một on its own and in the teens, but reads mốt when it follows a tens digit of two or more. So 1 is một, 11 is mười một, but 21 is hai mươi mốt. The tool applies this automatically.

When is 5 read as lăm instead of năm?

A standalone five is năm, but a units digit of 5 after any tens digit is read lăm. Thus 15 is mười lăm and 25 is hai mươi lăm. This avoids confusion with năm meaning year and is built into the converter.

What is the lẻ in một trăm lẻ năm?

When a tens place is zero but a lower place is not, Vietnamese inserts lẻ (or linh in the north) as a filler. So 105 is một trăm lẻ năm, literally one hundred and five. The tool inserts it wherever a place is skipped.

Which scale words does it use?

It groups digits in threes and labels them nghìn (thousand), triệu (million), and tỷ (billion), the standard Vietnamese scale words. Numbers up to twelve digits, into the hundreds of billions, are supported.

Does it handle the reading of 4 as tư?

Yes. A units digit of 4 after a tens digit is commonly read tư rather than bốn, so 24 is hai mươi tư. The tool uses the tư reading in that position, which is the everyday spoken form.

Vietnamese Number to Words

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This converter turns whole numbers into their Vietnamese spelled-out form, the way you would read them aloud or write them on a cheque. It implements the real contextual rules that make Vietnamese number reading famously tricky.

How it works

The number is split into groups of three digits from the right, and each group is labelled with its scale word: nghìn (thousand), triệu (million), or tỷ (billion). Within each group the tool reads hundreds, tens, and units while applying the special cases:

1 units after tens ≥ 2  → mốt   (21 = hai mươi mốt)
4 units after a tens     → tư    (24 = hai mươi tư)
5 units after a tens     → lăm   (15 = mười lăm)
zero tens, nonzero units → lẻ    (105 = một trăm lẻ năm)
tens = 1                  → mười  (11 = mười một)

Example and notes

The number 1,975 reads một nghìn chín trăm bảy mươi lăm, and 2,000,005 reads hai triệu không trăm lẻ năm. Use the lẻ form shown here for everyday speech; some northern dialects say linh instead, which is equally correct. The converter is designed for amounts in words on invoices, contracts, and cheques where precise, conventional readings matter.