Vietnamese age: tuổi mụ and tuổi thực
The same two-count structure as its neighbours — one at birth, a year added at the lunar new year — but on a calendar Vietnam computes for itself, at its own meridian. That last detail is the one this site has to be careful about.
The two counts
| Count | How it is reckoned | Where it applies |
|---|---|---|
| tuổi mụ (also tuổi ta) — nominal age | One at birth; a year added at Tết rather than on the birthday. | Family and everyday speech, fortune-telling and the can chi, and traditional observances. |
| tuổi thực (also tuổi tây) — full age | Years completed since birth; increments on the birthday. | Documents, law, school, medicine. |
Tuổi mụ is literally the "midwife age" — the count that reckons a child as already a year into life at birth. Tết Nguyên Đán, the lunar new year, is when it advances, so someone born days before Tết reaches two while still a newborn.
Can chi
A Vietnamese year carries a can chi name: one of ten can (heavenly stems) with one of twelve chi (earthly branches), the same sixty-year cycle used across the region, in Vietnamese — Giáp Thìn, Ất Tỵ, Bính Ngọ. The cycle turns at Tết, not on 1 January.
The animals attached to the branches are not the same everywhere. Vietnam's fourth branch, Mão, is the cat where China's 卯 is the rabbit, and the second is usually given as the buffalo rather than the ox. Because of that, this site prints the can chi name for a Vietnamese birth and no animal at all: naming the wrong animal for someone's own year is exactly the kind of small confident error §14 of this project's brief exists to prevent.
Which calendar produced these numbers
Computed from the Chinese lunisolar tables. Vietnam reckons its lunar months at UTC+7 rather than UTC+8, so Tết can fall a day either side of Lunar New Year.
That is a real limitation, not a formality. Vietnam computes its lunar months against UTC+7 and China against UTC+8, and a new moon that falls close to midnight lands on different days under the two — which moves a month boundary, and occasionally moves Tết a day away from Chinese Lunar New Year. In rare years the two calendars differ by a whole month.
So: where a birth is well clear of Tết, the figures below are right. Where it falls within a day or two of the lunar new year, or in a year where the two calendars diverge, tuổi mụ and the can chi here may be a year out. A Vietnamese-computed dataset would close that gap and is not yet built; until it is, this page states the gap rather than papering over it.
Source of the underlying tables: Hong Kong Observatory,Gregorian–Lunar Calendar Conversion Table, ingested 2026-08-18, covering1901–2099. Outside that range this site declines to answer.
Prose last reviewed 2026-08-19.
Worked examples
Computed on 20 August 2026 in the Asia/Ho_Chi_Minh zone, at build time, subject to the caveat above.
| Birthdate | Can chi of birth year | tuổi mụ | tuổi thực |
|---|---|---|---|
| Born 3 February 2024 — a week before the lunar year turned | Quý Mão | 4 | 2 |
| Born 12 February 2024 — the first days of the new lunar year | Giáp Thìn | 3 | 2 |
| Born 9 July 1995 — a birthday well clear of the boundary | Ất Hợi | 32 | 31 |
The first two rows are nine days apart and a year apart in both the can chi and tuổi mụ, which is the whole mechanism in one comparison. TheLunar New Year reference table gives the Chinese date for every year from 1901 to 2099; Tết is that date, give or take the day described above.
For the same structure computed on the Chinese calendar proper, seeChinese age; for the version that turns on 1 January instead, seeKorean age.