--- title: "Parabolic SAR (SAR): Formula, Meaning" description: "Parabolic SAR (Stop and Reverse), created by J. Welles Wilder Jr., is a series of points that trail price and accelerate toward it as a trend extends. When..." canonical: https://www.getswoopr.com/indicators/trend/parabolic-sar/ source: "Swoopr Investment: https://www.getswoopr.com" --- ## Direct Answer > Parabolic SAR (SAR) is an iterative trend-following stop-and-reverse overlay that accelerates toward price as a trend extends. A higher reading generally means not a scalar; dots below price generally denote an uptrend and dots above price a downtrend; a lower reading generally means not a scalar; interpretation depends on dot location and flips. The main limitation is that it tends to whipsaw in sideways markets and depends on the acceleration-factor settings. # Parabolic SAR (SAR): Formula, Meaning, Signals, Examples and How to Use It ## How Is Parabolic SAR Calculated? Parabolic SAR (Stop and Reverse), created by J. Welles Wilder Jr., is a series of points that trail price and accelerate toward it as a trend extends. When price touches the point, the indicator reverses to the other side of price. **Formula:** `SAR(next) = SAR + AF * (EP - SAR), where EP is the extreme point of the current trend and AF is the acceleration factor` **Inputs:** - Bar high and low prices - Starting acceleration factor 0.02 and step 0.02 - Maximum acceleration factor 0.20 (Wilder's defaults) - Extreme point: the highest high in an uptrend or lowest low in a downtrend **Worked example.** With a SAR of 100, an extreme point of 110 and an acceleration factor of 0.02, the next SAR is 100.20. The inputs are illustrative numbers, not market data. **Reading it.** SAR points below price describe an uptrend and points above price a downtrend, and a flip from one side to the other marks a reversal in the indicator. The acceleration factor rises each time a new extreme point is set, so the points tighten toward price as a trend ages. **Limits.** It tends to whipsaw in sideways markets, flipping repeatedly as price drifts back and forth across the points. Results also depend on the acceleration-factor settings, and the indicator always has a position, so it never signals a neutral market. ## Indicator snapshot | Attribute | Value | | --- | --- | | Abbreviation | SAR | | Category | Trend | | Creator / origin | J. Welles Wilder Jr. | | Primary inputs | High; Low; acceleration factor | | Common settings | AF 0.02, step 0.02, max 0.20 are Wilder defaults | | Output | Line/scalar | | Typical range | Price overlay | | Primary purpose | Describe trend direction, persistence, strength, or a smoothed price reference. | | Main limitation | It tends to whipsaw in sideways markets and depends on the acceleration-factor settings. | ## What is Parabolic SAR? Parabolic SAR is an iterative trend-following stop-and-reverse overlay that accelerates toward price as a trend extends. It should be treated as a transformation of observable market data, not as an independent source of truth. The useful question is not whether the indicator is “bullish” or “bearish” in isolation, but what specific market property it measures, which assumptions enter the calculation, and whether that information is already duplicated by another tool on the chart. For Swoopr, the canonical profile should separate definition, calculation, interpretation and decision use. That keeps readers from collapsing a descriptive metric into a trading strategy. An indicator can describe trend, momentum, volatility, participation, positioning or risk without providing a complete entry, exit, sizing or portfolio decision. ## What does it measure and why is it used? Describe trend direction, persistence, strength, or a smoothed price reference. The practical value is repeatability: the same inputs and formula can be applied across a defined dataset, allowing users to compare readings through time or across instruments when the calculation convention is held constant. The calculation can still be misleading if the data source, session, adjustment method, smoothing rule or parameter set changes. Two platforms can legitimately report different readings while using different assumptions, so check which conventions a chart uses. ## Formula **SARnext = SARcurrent + AF×(EP−SAR_current), with trend-specific reset rules** ### Calculation discipline 1. Fix the instrument, timeframe and session before computing the indicator. 2. Use one documented price/volume source and one corporate-action convention. 3. State every lookback, smoothing method and reset rule. 4. Handle missing data and zero denominators explicitly. 5. Reproduce at least one worked example from raw inputs during QA. 6. Compare the implementation with a second independent calculation before publication. ## How to read Parabolic SAR A higher reading generally means **not a scalar; dots below price generally denote an uptrend and dots above price a downtrend**. A lower reading generally means **not a scalar; interpretation depends on dot location and flips**. That interpretation is descriptive, not predictive. The same numerical state can lead to different outcomes in a strong trend, quiet range, event-driven gap or illiquid market. ### Bullish, bearish and neutral context A bullish interpretation is appropriate only when the reading lines up with the indicator's actual job. For a trend tool, that means direction or trend persistence; for a momentum tool, it means stronger upside momentum; for a volatility measure, “higher” is not bullish at all:it only means larger expected or realized movement. A generic bullish or bearish label therefore does not fit a direction-neutral indicator. A neutral state should be defined when the indicator does not provide enough evidence for its intended job. This is especially important for bounded oscillators near mid-range, volatility gauges near historical medians, or spread measures near long-run norms. ## Common settings The common reference is **AF 0.02, step 0.02, max 0.20 are Wilder defaults**. This is a starting convention, not a universally optimal parameter. Shorter lookbacks generally respond faster and produce more state changes; longer lookbacks smooth noise but react later. Parameter selection should be tied to the intended decision horizon, then tested over multiple instruments and regimes rather than optimized to one historical period. ## Worked hypothetical interpretation Suppose a researcher calculates Parabolic SAR with the documented settings across a liquid security and observes a material change in the reading. The first step is to state what changed in the underlying input. The second is to ask whether price structure, volume, volatility or the benchmark environment confirms that interpretation. The third is to define what observation would invalidate it. Only after those steps should the indicator feed a strategy rule. This sequence prevents a common error: treating the indicator output as if it arrived independently of the price, volume, options or market data used to calculate it. ## Best and weak market conditions Parabolic SAR (SAR) is most useful when the market property it measures is actually relevant to the decision. It is weakest when the regime changes faster than the lookback, the market is illiquid, the input data are incomplete, or the chosen parameter set is mismatched to the timeframe. A trend indicator tends to struggle in ranges; a mean-reversion oscillator can remain extreme during persistent trends; volume-based measures can break when venue coverage changes; options and on-chain measures can be provider-specific. ## Strengths - The trailing point is calculated mechanically from the extreme point, so it gives a rule-based level that does not depend on judgment. - The increasing acceleration factor makes the points close in on price as a trend extends, so the stop level tightens over time. - Reproducible when the formula and data convention are fixed. ## Weaknesses and false signals - It tends to whipsaw in sideways markets and depends on the acceleration-factor settings. - Parameter changes can alter timing and classification. - Correlated indicators can create false confidence by repeating the same underlying information. - Historical relationships can fail after market structure or volatility regimes change. - Backtests can be overstated by look-ahead bias, survivorship bias, unrealistic fills or omitted transaction costs. ## Combining Parabolic SAR with other indicators The strongest combination usually pairs different input families rather than similar formulas. Before adding another indicator, identify the specific error it is supposed to catch and measure how often the two signals disagree. High agreement between two price-only oscillators is not necessarily confirmation; it can be arithmetic redundancy. Related entities for this profile include: Aroon, Average Directional Index, Choppiness Index, Exponential Moving Average, Ichimoku Cloud, MACD. ## When not to use it Do not use Parabolic SAR as a standalone forecast or as a substitute for position sizing, liquidity checks, execution planning or fundamental research when those are relevant to the decision. Avoid publishing “best settings” without a defined asset universe, timeframe, cost model and out-of-sample validation. If the indicator depends on proprietary or provider-specific methodology, the provider's own documentation is the authority on how it is calculated. ## Practical checklist - [ ] What exact question is the indicator answering? - [ ] What data series, session and adjustments are used? - [ ] What parameters and smoothing rules are fixed? - [ ] Is the indicator bounded, unbounded or price-denominated? - [ ] Does a second indicator add independent information? - [ ] What market regime is present? - [ ] What would invalidate the interpretation? - [ ] Have slippage, costs and execution constraints been considered? - [ ] Has the calculation been independently reproduced? ## Frequently asked questions ### Is Parabolic SAR a buy or sell signal? No. It is an analytical measure. A trade still needs a hypothesis, trigger, invalidation rule, position size, exit logic and realistic execution assumptions. ### What is the best setting for Parabolic SAR? There is no universal best setting. Start with the conventional reference (AF 0.02, step 0.02, max 0.20 are Wilder defaults) and test nearby values across instruments, regimes and out-of-sample periods. Favor stable parameter regions over one historical winner. ### Can Parabolic SAR be used by itself? It can describe its specific market property by itself, but using it alone generally leaves other important dimensions:direction, regime, participation, valuation, liquidity or risk:undefined. ### Does Parabolic SAR work on every timeframe? The calculation may be portable, but behavior is not. A 14-period reading on a five-minute chart describes a very different market window from the same setting on a daily chart. Validate the exact timeframe. ### Why does Parabolic SAR give false signals? False signals arise from lag, noise, regime changes, parameter sensitivity, data conventions and the fact that market participants react to new information after the reading is calculated. ### How should Parabolic SAR be backtested? Write rules before testing, use point-in-time data, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample, break results out by regime and compare with a simpler baseline. ## Related Swoopr content - Parent hub: [Trend Indicators](https://www.getswoopr.com/indicators/trend/) - Related guide: [Parabolic SAR Explained](https://www.getswoopr.com/technical-analysis/trend-indicators/parabolic-sar/) - Related indicators: Aroon, Average Directional Index, Choppiness Index, Exponential Moving Average, Ichimoku Cloud, MACD ## Sources and further reading - [TA-Lib Functions](https://ta-lib.org/functions/) - [TradingView built-in indicator list](https://www.tradingview.com/charting-library-docs/latest/ui_elements/indicators/Indicators-List/) ## Editorial and risk note This page is educational content, not individualized investment advice. It does not imply guaranteed prediction, accuracy or outperformance. ## Frequently Asked Questions Is Parabolic SAR a buy or sell signal? No. SAR points below price describe an uptrend and points above price a downtrend, and a flip from one side to the other marks a reversal in the indicator. It tends to whipsaw in sideways markets, flipping repeatedly as price drifts back and forth across the points. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions. What is the best setting for Parabolic SAR? Parabolic SAR takes these inputs: bar high and low prices; starting acceleration factor 0.02 and step 0.02; maximum acceleration factor 0.20 (Wilder's defaults). There is no universal best setting for the tunable ones, so test them across instruments, regimes and out-of-sample periods and favor stable parameter regions over one historical winner. Can Parabolic SAR be used by itself? It tends to whipsaw in sideways markets, flipping repeatedly as price drifts back and forth across the points. Results also depend on the acceleration-factor settings, and the indicator always has a position, so it never signals a neutral market. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone. Does Parabolic SAR work on every timeframe? The calculation (SAR(next) = SAR + AF * (EP - SAR), where EP is the extreme point of the current trend and AF is the acceleration factor) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it. Why does Parabolic SAR give false signals? A reversal is triggered by a touch of the SAR point, so a single wide-ranging bar or gap can flip the indicator even when the trend has not changed. Raising the starting or maximum acceleration factor makes the points hug price and flip often, while lowering them makes the indicator slow to turn. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated. How should Parabolic SAR be backtested? Rebuild Parabolic SAR from bar high and low prices using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline. S Swoopr Editorial Team The Swoopr Editorial Team produces independent investment education, research, and tools for understanding markets, evaluating opportunities, and managing risk. All content is educational only and does not constitute personalized investment advice. See our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/).