Mấy vs Bao Nhiêu vs Mấy Giờ — Asking About Numbers and Time

Quick Answer

Mấy asks about small, countable numbers (typically under 10) and implies the speaker expects a low answer. Bao nhiêu asks about any quantity or amount without implying a range, and is also used for prices and large numbers. Mấy giờ is a fixed phrase specifically for asking what time it is, combining mấy with giờ (hour/o'clock).

Comparison Table

Detailed Explanation

Mấy — Asking About Small Numbers

Mấy (Hán-Việt root: 幾 kỉ) functions as an interrogative word equivalent to "how many" in English, but it carries an important implication: the speaker assumes the answer will be a relatively small number, generally between one and nine. When the expected answer could be ten or higher, bao nhiêu is more natural.

In sentence structure, mấy typically comes directly before the noun it modifies, often accompanied by a classifier. For example, to ask how many children someone has, you place mấy before the classifier đứa and noun con. This mirrors patterns in Chinese (幾個) and Japanese (何個), making it intuitive for East Asian learners.

Common contexts for mấy include: asking about the number of siblings, children, floors in a building, days remaining, and the age of young children (under ten). It is conversational and slightly informal in feel.

Bao Nhiêu — Asking About Any Quantity or Price

Bao nhiêu is the more neutral and versatile interrogative, covering both "how many" for countable nouns and "how much" for uncountable nouns or prices. Unlike mấy, it places no upper limit on the expected answer, making it appropriate whenever the quantity could be large or unknown.

When asking about prices — one of the most common uses for A1 learners — bao nhiêu is always used, never mấy. The phrase bao nhiêu tiền (how much money) is essential for shopping vocabulary. Similarly, when asking about age for adults, population figures, distances, or weights, bao nhiêu is the correct choice because the answer range is open.

Structurally, bao nhiêu can appear after the noun or at the end of the sentence. For prices, it most often follows tiền (money): bao nhiêu tiền? It can also precede the noun in some patterns: bao nhiêu người (how many people).

Mấy Giờ — Asking About Time

Mấy giờ literally means "how many hours" but functions as the standard phrase for asking "what time is it?" The word giờ means both "hour" and "o'clock," and since clock hours only run from 1 to 12 (or 24 in the 24-hour system), the small-number assumption of mấy fits perfectly here. That is why mấy giờ — and not bao nhiêu giờ — is used for time questions.

The phrase bây giờ là mấy giờ? (What time is it now?) is one of the first expressions A1 learners encounter. You can also ask about a scheduled time: cuộc họp lúc mấy giờ? (What time is the meeting?). The preposition lúc (at) is commonly paired with mấy giờ when asking about the time of an event.

Note that for minutes, Vietnamese uses phút, and for asking how many minutes, mấy phút is again preferred over bao nhiêu phút for small durations, while bao nhiêu phút is used for longer, open-ended durations.

Northern vs. Southern Usage

Both mấy and bao nhiêu are used throughout Vietnam with consistent meaning. However, in Southern Vietnamese speech, mấy is also commonly used as an informal second-person pronoun (similar to "you all" or an informal "you"), which is distinct from its interrogative function. Northern Vietnamese speakers rarely use mấy as a pronoun. Context always makes the intended meaning clear.

Example Pairs

Common Patterns

Common Mistakes

Mistake 1 — Using Mấy to Ask About Prices

Learners often assume that since mấy means "how many," it can be used to ask about prices. However, Vietnamese prices are always open-ended in range, so bao nhiêu is the only correct choice when asking how much something costs.

❌ Cái này mấy tiền?

✅ Cái này bao nhiêu tiền?

The phrase mấy tiền is not natural Vietnamese. Always use bao nhiêu tiền when shopping or asking about any monetary amount. This is one of the most essential fixed phrases for A1 learners.

Mistake 2 — Using Bao Nhiêu Giờ Instead of Mấy Giờ

Because bao nhiêu is the general "how many/how much" word, learners sometimes construct bao nhiêu giờ to ask about time. This phrasing is unnatural and not used by native speakers. The fixed expression for asking the time is always mấy giờ.

❌ Bây giờ là bao nhiêu giờ?

✅ Bây giờ là mấy giờ?

Clock hours are always a small number (1–12 or 1–24), which is why mấy fits naturally in this fixed phrase. Treat mấy giờ as a single vocabulary unit meaning "what time."

Mistake 3 — Using Mấy for Adult Ages

While mấy tuổi is appropriate for asking a young child's age, using it for adults sounds odd or even slightly rude, as it implies the speaker expects the person to be very young. For adults, bao nhiêu tuổi is the polite and correct form.

❌ Bà ấy mấy tuổi?

✅ Bà ấy bao nhiêu tuổi?

Reserve mấy tuổi for contexts where you are genuinely asking about a small child. When in doubt about someone's age range, always default to bao nhiêu tuổi to be safe and polite.

Mistake 4 — Omitting Giờ in Time Expressions

Learners sometimes drop giờ when stating or asking the time, treating mấy alone as sufficient. However, giờ is required in the question phrase and in answers when stating the o'clock time.

❌ Bây giờ là mấy?

✅ Bây giờ là mấy giờ?

When giving a time answer, also include giờ: Bây giờ là ba giờ (It is three o'clock). Omitting it makes the sentence incomplete and potentially confusing.

Mistake 5 — Using Mấy for Large or Unknown Quantities

When the quantity being asked about is large or completely unknown, using mấy instead of bao nhiêu sounds unnatural because mấy implies an expectation of a small number. This mismatch is jarring for native speakers.

❌ Thành phố Hồ Chí Minh có mấy người?

✅ Thành phố Hồ Chí Minh có bao nhiêu người?

When asking about populations, large quantities of items, or any situation where the answer might be in the tens, hundreds, or millions, always use bao nhiêu.

Quick Quiz

Fill in the blank with mấy, bao nhiêu, or mấy giờ:

Question 1: Chuyến tàu khởi hành lúc _____?

Hint: You are asking about the departure time of a train.

Question 2: Vé máy bay _____ tiền?

Hint: You want to know the price of a plane ticket, which could be any amount.

Question 3: Nhà bạn có _____ tầng?

Hint: You are asking how many floors someone's house has — likely a small number.