You usually start with 7 dominoes in most basic games (like classic Block or Draw) when playing with 2 players.

However, different rules and player counts change that:

  • 2 players: 7 tiles each is standard in Block/Draw.
  • 3–4 players: often 5 tiles each, with the rest forming the “boneyard” to draw from.
  • Some fives-style games or house rules (especially casual 1‑on‑1) use 9 tiles each to make hands more strategic.

So if your question is general, the safest quick answer is:
Start with 7 dominoes per player in a standard 2‑player game using a double‑six set.