Stop and Reverse (SAR) Indicator

Welles Wilder's Parabolic Stop and Reverse (SAR) is a trailing stop-based trading system; it is often used as an indicator as well. The SAR uses a trailing stop level that follows prices as they move up or down. The stop level increases speed based on an "Acceleration Factor." When plotted on the chart, this stop level resembles a parabolic curve, thus the indicator's name. The parabolic function accepts three parameters. The first two control the acceleration during up and down moves, respectively. The last parameter determines the maximum acceleration.