The internet did not prepare me well for the way Vietnam uses currency. And I tried to prepare myself really. Because, if you tried to prepare yourself as well, you would have known that Vietnamese Dong starts in the thousands. They use period as a thousand separator. They use commas for the cents.
Whatever experiences you had with money elsewhere, Vietnamese Dong will betray you. Even if you have converted your currency to Dong and just abandon how much your Vietnam cash converts to the cash of your own country.
Because the separators don't fucking matter.
Mixed Signals
Here is where you will trip up. In daily Vietnam transactions, decimals don't mean a thing.
The lowest currency is 1000 dong. Anything less than that is rounded up.
Vietnam currency uses paper cash. In that cash, the period separator comes up.
Elsewhere, that period separator is irrelevant. You'd see signages using spaces and commas in substitute of the period separator.
When engaging with locals online, some of them would not bother with the period separator. If the period separator matters so much that it is enshrine in the currency itself, why don't daily transactions and price labels use it consistently?
Like literally, you'd see cafes do away with the three zeroes as well, and it will throw you off drastically.
Your vietnam currency reminder
So repeat after me:
The separators are irrelevant.
The decimals are irrelevant.
The lowest currency is 1000 dong.
Anything less than 1000 dong is rounded up.
Always assume that any price written without three zeroes are still that price times a thousand, unless corrected
In the context of the Philippine currency operations (not value), a 1000 dong would approximate 1 pesos and 000 cents. And the vietnamese alternative for centavos would approximate values less than Filipino cents. So if in Dong, you say 1000,999, or a thousand dong and 999 cents, that would be just a peso, and 1cent rounded up, or rather 0.999 cents.
So when reading local prices in vietnam, regardless of how it is written, always start from 1000. If the three zeroes are not written, assume that they are there. 500k is the largest paper currency in circulation; this is close to a 1000 Philippine pesos as of writing (2025). So their 50k dong currency is the Filipino's 100 pesos; and their 100k dong is the Filipino's 200 pesos.
And if any confusion comes up, think of the Vietnamese price that is the most sensible, and in multiples of a thousand.
Hope this helps you not trip up on your Grab travel and accidentally misread the 7000 dong entrance fee for the airplane as 7mil dong, all because you misread the period separator in the currency as a decimal especially when that Grab message did not employ the period separator as well. Damn that was a frustrating first day experience; and the driver's lack of English competency did not help.
Additional communication tips in Vietnam
Vietnamese are very helpful. But they are also very expressive, for better or worse. Some may call it boisterous or callous. But you do notice the strong tones when they communicate with fellow locals in the back kitchen in contrast to the polite hesitation they do with foreigners.
Many of them, especially those who aren't in tourist-heavy areas, aren't English literate. The closest thing that you'd encounter with them when it comes to English literacy is in the Vietnam Dong, which will make buying things not as painful. Elsewhere, if you had to engage with a Vietnam local that you can sense don't always engage with foreigners, you may have to employ Google translate.
For Grab drivers, other than Google translate, you may have to communicate with photos of your location. You'd have to do a lot of visual pointing at times.
When doing directions, addresses and street names are more reliable indicators of locations than landmarks. Telling where you are close, if that happens to be a commercial area, will likely fail, as many visible store brands are often a walk apart from each other.
That's what I've picked up in my short stint in Vietnam. But it was my first foray abroad. Hope this helps, or if not, at least help you get closer to the tips and tricks that will actually help you in your visit.