In this rule

Historical Rules · 27 April 2018

Rule 905.1a

Official source text from the 27 April 2018 Rules release

A draft typically consists of three draft rounds. In each draft round, each player opens a booster pack, drafts one card by placing that card in a face-down pile in front of the player, then passes the remaining cards to the next player. Each player then drafts a card from the booster pack passed to them and passes the remaining cards. This procedure continues until all cards in that draft round have been drafted.

Find this number in the current Rules