The parabolic SAR, or parabolic stop and reverse, is a popular indicator that is mainly used by traders to determine the future short-term momentum of a given asset. The indicator was developed by the famous technician J. Welles Wilder Jr. and can easily be applied to a trading strategy, enabling a trader to determine where stop orders should be placed. (The calculation of this indicator is rather complex and goes beyond the scope of how it is practically used in trading.)
One of the most interesting aspects of this indicator is that it assumes a trader is fully invested in a position at any point in time. For this reason, it is of specific interest to those who develop trading systems and traders who wish to always have money at work in the market.
The parabolic SAR indicator is graphically shown on the chart of an asset as a series of dots placed either above or below the price (depending on the asset's momentum). A small dot is placed below the price when the trend of the asset is upward, while a dot is placed above the price when the trend is downward. As you can see from the chart below, transaction signals are generated when the position of the dots reverses direction and is placed on the opposite side of the price.
As you can see from the right side of the chart, using this indicator by itself can often lead to entering/exiting a position prematurely. So, many traders will choose to place their trailing stop loss orders at the SAR value, because a move beyond this will signal a reversal, causing the trader to anticipate a move in the opposite direction. In a sustained trend, the parabolic SAR is usually far enough removed from price to prevent a trader from being stopped out of a position on temporary retracements that occur during a long-term trend, enabling the trader to ride the trend for a long time and capture substantial profits.
The parabolic SAR performs best in markets with a steady trend. In ranging markets, the parabolic SAR tends to whipsaw back and forth, generating false trading signals. Wilder recommended augmenting the parabolic SAR with use of the average directional index (ADX) momentum indicator to obtain a more accurate assessment of the strength of the existing trend. Traders may also factor in candlestick patterns or moving averages. For example, price falling below a major moving average can be taken as a separate confirmation of a sell signal given by the parabolic SAR.
For more on this indicator, see "Introduction to the Parabolic SAR."