Drop three zeros to roughly convert VND to USD divided by 25. 100,000 VND ≈ $4. 25,000 ≈ $1.
This quick math saves you from accidentally overpaying. A 'cheap' 200,000 VND coffee is actually $8 — overpriced for Vietnam.
For reference: a bowl of phở: 40k–80k VND. Bia hơi: 5k–10k. Grab car across town: 100k–200k. Coffee: 25k–60k.