How to Read Supertrend: The ATR Trailing Line and Its Flaws

What Supertrend draws

Supertrend draws a single line below or above price to show whether the market is currently on the up side or the down side. While it reads bullish, the line follows price up from below; while it reads bearish, it follows price down from above. The distance between the line and price is set by ATR (average true range), so the more a coin swings, the farther away the line sits. ATR itself is covered in the article on measuring volatility with ATR. The reason for tying the distance to volatility is simple. A narrow line on an instrument that swings widely every day gets pierced by ordinary noise, and a wide line on a quiet instrument reacts only long after the trend has turned. Supertrend draws, as a single line, the rule that the direction counts as changed only when a counter-move several times the usual swing appears. So there are only two things to look at on the screen: whether the line is below or above price, and how far apart the line and price are. The closer they are, the smaller the counter-move needed to flip the direction.

Formula: midpoint ± multiplier × ATR

For each bar, two candidate lines are calculated first. The upper band is (high + low) / 2 + multiplier × ATR, and the lower band is (high + low) / 2 − multiplier × ATR. The defaults for TradingView's built-in Supertrend are a 10-bar ATR and a multiplier (factor) of 3, and this site's Supertrend Scanner and backtester use the same defaults. Because ATR is a Wilder-style average, the values over the first few dozen bars can differ slightly depending on where the calculation starts. In an uptrend the lower band, and in a downtrend the upper band, becomes the Supertrend line you see on the chart. Note that the center is (high + low) / 2, not the close. Because it is the middle of the bar, on a bar with a long wick the center can sit quite far from the close. ATR averages the true range, which includes not only the high-low distance but also the distance from the previous close, so a bar that opens far from the previous close raises ATR and pushes the line farther away. If lines in different programs look slightly different, the order of checks is to match the ATR averaging method (Wilder, simple or exponential) and the number of bars loaded.

The rule that lets the line move only one way

The key to Supertrend is that the line never steps back. In an uptrend, the line is raised only when the newly calculated lower band is higher than its previous value; if it is lower, the previous value is kept. So while price rests or pulls back, the line stays flat, as in the figure, and when price rises again, the line follows it up. It is also called a ratchet, after the gear that turns only one way. In a downtrend, the reverse applies: the upper band only moves down. The only time the line steps back is when a close crosses it and the direction flips. This rule has consequences. When a pullback drags on, price comes down while the line stays put, so the gap between them narrows until even a small drop can pierce the line. Conversely, when volatility rises, the newly calculated band moves lower, but the line does not come down, so it does not widen to match the bigger swings. Many people read a flat line as 'support that is holding', but it is only a value calculated on some past bar that has stopped moving; it does not mean orders are gathered at that price.

Flips: when the close crosses the line

In an uptrend, a close below the lower line flips the direction to bearish; in a downtrend, a close above the upper line flips it to bullish. Because the close is what counts, a wick that pokes through the line mid-bar and comes back is not a flip. A cross on a bar that is still forming can disappear before the bar closes, so the Supertrend Scanner marks this separately as a 'pending flip'. When a flip happens, the line jumps to the opposite band, so on the chart it moves from below price to above it, or from above to below. Using the close means looking at the conclusion of the whole bar rather than momentary intrabar swings. The conclusion, however, depends on the bar length. The 1-hour chart may already have flipped to bearish while the daily is still bullish, and neither one is the right answer. When judging, decide on the bar length first and count only that bar's closes. Right after a flip the line jumps far to the other side, so flipping back on the very next bar is relatively rare, but in a range it can flip again within a few bars.

Using it as a trailing stop

Since the line follows price and never steps back, it is commonly used as a trailing stop. In an uptrend, that means closing the position when a bar closes below the line, and the distance to the line is the stop distance at that moment. Two things are worth knowing here. The flip is confirmed by the close, so the price at which the position is actually closed is often lower than the line. The flip bar in the figure closed about 1.7% below the line. And with a multiplier of 3, the line usually sits close to three ATRs away from price, so the stop distance is wider than you might expect. If you use leverage, the Futures Liquidation Calculator lets you check whether that stop would be reached before the liquidation price. A wider stop means a larger possible loss for the same position, so people who use the line as a stop often measure the distance to the line first and size the position to fit that distance. A common mistake is to think that placing a resting stop order at the line gives the same result. Intrabar orders fill on wicks, so the outcome differs from a rule based on the close.

Why it keeps flipping in sideways markets

In a trendless range, price crosses the line every time it travels between the top and the bottom of the range. A bullish flip is confirmed only after price has already risen a good deal, and a bearish flip only after it has already fallen a good deal, so following the flips as they come means buying near the top of the range and selling near the bottom, over and over. Following the flips in the figure at the close of each flip bar, all four buys made on bullish flips would have been sold at a lower price on the next bearish flip. These frequent false signals are called whipsaws, and they are a weakness shared by trend-following indicators. The effect is worst when the height of the range is similar to the line's distance. If the range is a few ATRs tall, every time price reaches an edge, the line sits at a distance that is easy to pierce. That is why it matters to spot a range first. When the gaps between flips get shorter, flips keep happening at similar price levels, and the line keeps jumping while staying flat, many people read it as a range. In such stretches, looking first at where the top and bottom of the range are explains the situation better than each individual flip.

What changes with the multiplier

A larger multiplier moves the line farther from price, so ordinary swings no longer cross it and flips become fewer. Using a multiplier of 5 on the same range cut the flips from nine to five. In exchange, flips come later, and because the line is farther from price when they do, more is given up each time. A smaller multiplier does the opposite. The ATR period matters too: the shorter it is, the more sensitive the line is to recent swings. There is no single right setting, and results differ by coin, bar length and period, so you can compare them in the backtester by changing only the setting under the same conditions. A common mistake when comparing is to pick the one setting with the best result and trust it as is. The more settings you test, the more likely one of them happened to fit the past by chance, so the order of checks is to run a setting chosen on one period again on a different period and see whether the results are similar. Each setting also produces a different number of flips, so a fair comparison includes fees and slippage. Changing the multiplier and the period together makes it hard to tell what changed the result, so change one at a time.

What Supertrend does not tell you

Supertrend's direction boils down, in a single line, to one question: has price moved against the current direction by more than a multiple of its recent swings? It does not tell you whether the trend will continue or how far price will go after a flip. Looking back over one long trend, its results can easily look good, but you only see the full picture when you also count the small losses that piled up in the ranges along the way. Results after flips were not measured in this article, and they can differ greatly between coins and bar lengths. Showing direction simply, with a single line, is both Supertrend's strength and its limit. Supertrend also does not use volume at all. It cannot tell a flip that came with a surge in trading from one that came during a quiet hour. That is why many people check volume, the direction on a higher bar length and nearby support and resistance separately when they see a flip. Rather than settling the direction on Supertrend alone, it fits the indicator's nature better to use it as a reference line that tells you the current verdict and where the close would have to cross for that verdict to change.

How it looks different in crypto and stocks

Crypto trades around the clock, so bars run into one another, and the daily close is just a time set by the exchange, not a moment when the market stops. Flips therefore tend to build up gradually within bars. Stocks build up news after the regular session closes, so the next open can start far from the previous close, and a single gap often crosses the line and confirms a flip at once. In that case trading may start well below the line you were using as a stop, so the loss you calculated from the distance to the line is not respected. Gaps are part of the true range, so ATR rises and the line moves farther away. Korean stocks have a daily price limit, so on a day that hits the limit you may not be able to trade as much as you want, while US stocks have no daily limit, only mechanisms that briefly halt trading during sharp moves. Large caps such as Samsung Electronics and SK Hynix, and US indexes, usually swing less than crypto, so the line tends to sit closer to price with the same multiplier; rather than carrying the multiplier over unchanged, look at the distance between the line and price first.

Reading it on a live chart

The last bar on a live chart has not closed yet, so each time its high or low changes, that bar's bands and ATR are recalculated and the line moves. If the forming bar crosses the line and comes back just before the close, the color and direction that changed briefly on screen revert. Every flip you see on past bars is the result of a closed bar, so a 'flip' seen on a live screen and what is left in the record can differ. That is why this site's Supertrend Scanner keeps the forming bar's state separately as a 'pending flip'. On a live chart, look at which side of the line this bar must close on for a flip, and how much time is left until the close.

Common mistakes

Because Supertrend's rules are simple, it is easy to misread. These are mistakes that come up often.

• Counting a temporary flip on a forming bar as a confirmed flip
• Treating a flat line as support or resistance where orders are gathered
• Placing an intrabar stop order at the line and expecting the same result as a rule based on the close
• Using the multiplier that worked best on one period unchanged on other instruments and periods
• Reading each flip as a new trend even as flips become frequent in a range