Parabolic SAR
Parabolic SAR (Stop and Reverse) is a trend-following indicator developed by J. Welles Wilder that places dots above or below price to indicate the potential direction of price movement and dynamic trailing stop levels.
J. Welles Wilder introduced the Parabolic SAR in his 1978 book New Concepts in Technical Trading Systems alongside other enduring tools such as the RSI and ATR. The term 'parabolic' referred to the curved trajectory the indicator's dots traced during strong trending moves, while 'SAR' stood for Stop and Reverse — the original intent was not merely to signal trend direction but to provide an active stop level that tightened as a trend accelerated, prompting traders to exit and potentially reverse their position.
The calculation involved an acceleration factor (AF) that started at 0.02 and increased by 0.02 each period a new extreme price was set, up to a maximum of 0.20. The formula was: SAR (next) = SAR (current) + AF × (Extreme Point − SAR current). In an uptrend the dots appeared below price, rising gradually at first and then accelerating as momentum built. In a downtrend the dots appeared above price, falling toward it. A signal occurred when price crossed through the SAR dots, at which point the dots flipped to the other side.
Indian intraday traders extensively used Parabolic SAR on NSE Nifty futures and index option positions for dynamic stop management. Because the dots accelerated as a trend extended, the SAR served as a trailing stop that allowed profits to run while providing a concrete exit level. On the 15-minute chart of Nifty 50 futures, the SAR was frequently combined with ADX to filter signals — trades in the direction of the SAR flip were considered only when ADX confirmed a trending environment, thereby avoiding the choppiness that caused frequent whipsaws during range-bound sessions.
The indicator's primary weakness was its behaviour during sideways markets. When price oscillated within a narrow range, the SAR flipped back and forth repeatedly, generating a succession of false signals and small losses. Practitioners therefore used volume analysis and the ADX to assess whether market conditions were suitable for SAR-based strategies before applying them mechanically.
Another nuance specific to Indian F&O markets was expiry-week dynamics. As weekly and monthly Nifty and Bank Nifty options approached expiry, intraday volatility often compressed as open interest in at-the-money strikes became dominant. During these sessions, SAR signals on shorter timeframes were considered less reliable, and many traders switched to observing the indicator only on hourly or daily charts to maintain a cleaner perspective.