Parabolic SAR (Stop and Reverse) is an indicator developed by J. Willes Wilder to discover and exploit profitable trends in all kinds of markets. It is a popular tool among technical traders, and a straightforward and as a simple mechanism for analyzing the markets, it offers some unique advantages over other tools.
Below we have a chart of the EURUSD pair depicting the Parabolic SAR in action. We observe that the indicator was able to capture many small reversals with remarkable accuracy. And in those cases where it failed, we see that the thrust of the market action was strong enough to place it into a correct configuration, thereby minimizing the potential losses of a faulty trade.
Calculation of the Parabolic SAR
Parabolic SAR is calculated by a recursive formula which ties the prices of one period to another through simple arithmetics.
SAR of Today = SAR of Yesterday + a (EP- SAR of Yesterday)
SAR of Tomorrow = SAR of Today + a(EP-SAR of Today)
EP is the maximum recorded during the time period in consideration. If during each period of analysis a new record is broken, the EP will be updated accordingly, and the SAR value will change.
“a” represents the acceleration factor. It is set at 0.02 in the beginning, and reset each time a new EP is achieved. This is to ensure that the indicator’s value will come closer to the EP value every time a new record is broken, but the maximum value for the EP is usually set at 0.2 in order to prevent it from becoming too large and distorting the analytical picture. Due to the higher volatility of the forex market, traders prefer to give an initial value of 0.01 to the acceleration factor on the basis that frequent fluctuations, leaps and bounces in the price action do not justify attaching a lot of significance to arbitrary price highs.
Once the SAR value is calculated one of two courses will be taken in order to derive the signal from the indicator. If tomorrow’s SAR remains within today’s or yesterday’s price range, the indicator is set at the lowest price during that time period. For example, if the SAR is slightly above yesterday’s opening lowest price, or close to, but below, yesterday’s high, the indicator will be set at today’s lowest price.
If on the other hand, tomorrow’s SAR value is within tomorrow’s price range, the indicator will switch sides. If it is below the price action, it will move to the upside, and if it was on the upside it will come below, signifying a trend switch.
Trading with Parabolic SAR
Parabolic SAR is generally regarded as a trend indicator, since other types of markets tend to generate false signals leading to whipsaws and fake breakouts. The best way of trading the Parabolic SAR is to first gauge the direction of the market by using simple tools like trend lines, moving averages, or tools like the average true range, before using Parabolic SAR to trade the shorter-term fluctuations that can be exploited within a longer term framework.
When it is drawn on a chart, the Parabolic SAR will indicate a bullish market if it remains below the price, or supports it, and when it is above the same it is regarded to be suppressing the prices, indicating bearish conditions. Not only is it possible to regard this phenomenon as a signal for the opening of a position, but it also makes sense to use the Parabolic SAR as a stop or take profit level in each trade. For instance, when the price action is bearish, and we have a sell order, one can choose to exit the position when the price action approaches the SAR level by a predetermined number of pips. When the market action is bullish on the other hand, we can use the Parabolic SAR as a support level, and when the price gets too close to it, we can liquidate the trade. It is also possible to use a time-stop while trading with this indicator. In this case, there is no necessity of a market reversal. Instead we determine a timeframe during which the trade will be kept active, but when that period is out, we’ll liquidate it even if the Parabolic SAR indicator is indicating positive conditions. This course of action is justified on the basis that in a strongly trending market where this indicator is most useful, lack of progress can be a sign of approaching reversal.
This indicator is most useful in a trending market. It is best to use it in combination with other indicators that establish the general direction of the trend at a higher level, while trading short-term volatility with the SAR. The advantages of this technical tool are its simplicity, clarity of signals, ease of interpretation, and tendency to generate concrete points of action during a trending market. These same strengths are also the weaknesses of the indicator. It is sometimes the case that the solid signals of the SAR indicator lack any practical basis. To avoid such conditions, we suggest that you use the SAR indicator with oscillators that signal emerging divergence/convergence scenarios, so that the common problem of whipsaws are reduced in frequency. Ultimately, of course, our best guide should always be money management and prudence in trading, beyond any single technical indicator