What is One-Chip Rule in Poker?

The one-chip rule is a rule stating that placing one chip in the pot, even if it a higher denomination than necessary, is considered a call unless the player announces a raise beforehand.

For example, if it’s $10 to call a bet and you throw in a $100 chip without announcing “raise” when the action is on you, that action will be counted as a call (you’ll get $90 back).