Trend & directionParabolic SAR · SAR
Wilder's stop-and-reverse dots that trail price and accelerate, flipping sides when the trend breaks.
Works best in trending marketsEngine-computed on a fixed sample series
What it is
The Parabolic SAR — short for “stop and reverse” — is a trend-following tool that prints a single dot on each bar, sitting either just below price in an uptrend or just above it in a downtrend. J. Welles Wilder Jr. designed it in 1978 as an always-in-the-market system that answers one question: where should my trailing stop be right now, and at what point has the trend flipped? The dots trace a parabola-like curve that starts far from price and tightens toward it as a trend matures, so the exit noose gradually closes. When price finally touches the dot, the indicator flips to the other side of price, simultaneously stopping you out of the old position and proposing a new one in the opposite direction. For a beginner it is best pictured as an automatic, accelerating trailing stop that never lets a trend run without a defined exit.
How it is calculated
Each new dot is the prior dot plus an acceleration factor times the gap between the prior dot and the extreme point of the current trend — in words, the next SAR equals the current SAR plus AF times (extreme point minus current SAR). The extreme point is the highest high reached so far in an uptrend or the lowest low in a downtrend. The acceleration factor starts at 0.02 and steps up by 0.02 every time price makes a new extreme, capped at a maximum of 0.20, which is why the dots accelerate toward price the longer and stronger the trend runs. Wilder added a safeguard so the SAR can never move inside the prior two bars' range, preventing premature stop-outs. When price crosses the dot the position flips: the SAR resets to the last extreme point, the acceleration factor resets to 0.02, and a fresh extreme begins in the new direction.
Reading it, step by step
Dots below the candles mean the trend is up and you should be long or flat-to-long, while dots above mean the trend is down. The flip from one side to the other is the actionable event, because it is both an exit for the current position and an entry signal for a reversal. Since the dots ratchet closer as the acceleration factor climbs, a long, healthy trend shows dots hugging price tightly near its end, warning that the trailing stop has tightened. The distance of the dots from price early in a move is wide, giving trends room to breathe before the stop closes in. The tool never says nothing — it is always on one side or the other, which is its defining strength in a trend and its defining weakness in a range.
Best timeframes and settings
The default 0.02 step and 0.20 maximum are Wilder's originals and remain the standard across daily, intraday, and weekly charts; they suit swing and position trading on daily bars particularly well. Raising the step, say to 0.03, makes the dots accelerate faster and hug price more tightly, producing earlier exits but more whipsaws, while lowering it to 0.01 loosens the stop, letting trends run further at the cost of giving back more profit at the turn. Faster settings appeal to intraday momentum traders who want quick exits, while slower settings suit position traders riding multi-week trends. The key trade-off is the same one every trailing stop faces: tight stops lock in gains but get shaken out, loose stops ride trends but surrender more on the reversal. Most traders leave the defaults alone and instead control behavior through the timeframe they apply it to.
When and where to use it
The Parabolic SAR is built for trending markets and shines when a clear directional move is underway across stocks, futures, forex, and crypto. Its Achilles heel is the sideways market, where it flips back and forth generating a stream of small losing whipsaws, so it should be paired with a trend filter that switches it off in ranges. It is most useful as a trade-management and exit tool rather than a standalone entry system, because its assumption that you are always in the market does not match how most traders operate. On higher timeframes it produces fewer, more reliable flips, while on very short intraday charts the flips multiply and the noise rises. Reach for it when you already believe a trend exists and you want a disciplined, mechanical way to trail it.
Strategies that use it
The purest use is trend-trailing: enter on a signal of your own, then ride the position while the dots stay on the favorable side and exit or reverse the moment they flip. A stronger, filtered strategy layers ADX on top — take SAR long flips only when ADX is above 25, confirming a real trend, and ignore flips when ADX is low, which strips out most of the range-bound whipsaws. A third approach uses SAR purely as the trailing stop for a position entered on a moving-average crossover or breakout, letting the accelerating dots decide the exit while the other system decides the entry. In each case the golden rule is to demand trend confirmation before honoring a reversal flip, because in isolation the flip is only reliable when a trend is actually present.
Combining it with other indicators
The Average Directional Index is the classic partner because it measures the trend strength that SAR itself ignores — SAR tells you direction and stop level, ADX tells you whether to trust the signal at all. A longer-term moving average serves as a directional bias filter, so you only take SAR long flips while price is above the 200-day average. Momentum oscillators such as the MACD or RSI can confirm that a fresh flip has momentum behind it rather than being a dead-cat bounce. Some traders combine SAR with a volatility measure like the ATR or Bollinger Bands to judge whether the market is trending or compressing before acting on flips. The consistent theme is to marry SAR's excellent exit logic with something that judges regime, since SAR is blind to whether a trend exists.
Where it fails
In a choppy, directionless market the SAR flips on nearly every swing, whipsawing the trader into a death by a thousand cuts of tiny losses — this is its single greatest failure mode and the reason it must never be traded naked in a range. Because a flip is triggered by price merely touching the dot, sharp but shallow pullbacks in an otherwise intact trend can knock you out just before price resumes. The always-in-the-market assumption forces a position at all times, which is unrealistic and generates trades in conditions where standing aside is correct. The fix is a regime filter — ADX, a moving-average slope, or simple visual trend confirmation — plus the discipline to skip flips that fight the higher-timeframe trend. Traders also err by over-tightening the acceleration factor in pursuit of faster exits, which only multiplies the whipsaws.
A worked example
Imagine a stock trending up from 40 to 50 over several weeks. Early in the move the SAR dots sit around 38 to 39, a comfortable distance below price, and as each new high is made the acceleration factor climbs from 0.02 toward 0.10, dragging the dots up to 44, then 46, then 48 as price reaches 50. A minor pullback to 48.10 leaves the dot untouched, so you stay long, but when price slips to 47.90 and touches the dot at 48.00, the SAR flips above price — you are stopped out near 48.00, having captured most of the 40-to-50 run, and the indicator now proposes a short. If ADX had meanwhile fallen below 20, a disciplined trader would take the exit but decline the short, recognizing the trend has weakened into a possible range where fresh SAR flips would only whipsaw.