Professionals use the ATR for three core jobs: position sizing, volatility-based stop placement, and trailing stops on winning trades.
ATR serves as an element of position sizing, with the current ATR (or a multiple of it) used as the stop-loss distance when calculating trade volume based on risk tolerance, providing a self-adjusting risk limit.
Pros also use ATR for trailing stops, adjusting the stop-loss level as the market moves to lock in profits while still giving the trade room.
Critically, they treat ATR as a confirming indicator alongside other strategies, not as a directional signal.