{"format":"alysly-page/1","url":"https://alysly.com/learn/volatility/","json":"https://alysly.com/json/learn/volatility/index.json","lang":"en-US","title":"Bollinger Bands and ATR: Using Volatility Properly","description":"Bollinger bands, average true range and the squeeze: how volatility is measured and why it matters more for stops and position sizes than for signals.","published":"2026-08-02T15:41:33+02:00","modified":"2026-11-04T09:15:31+01:00","alternates":[{"lang":"de-DE","url":"https://alysly.com/de/lernen/volatilitaet/","json":"https://alysly.com/json/de/lernen/volatilitaet/index.json"}],"about":"Machine-readable version of the page at url. It contains the text, tables and key figures published there, but not the interactive charts and tools.","breadcrumb":[{"name":"Investing & Trading Basics","url":"https://alysly.com/learn/"},{"name":"Level 2","url":"https://alysly.com/learn/#level-2"},{"name":"Measuring Volatility: Bollinger and ATR","url":"https://alysly.com/learn/volatility/"}],"content":[{"type":"paragraph","text":"Level 2 Patterns & Indicators · Part 8/9"},{"type":"heading","level":1,"text":"Measuring Volatility: Bollinger and ATR"},{"type":"paragraph","text":"By Alexander Bock, founder and data analyst","links":[{"text":"Alexander Bock","href":"https://alysly.com/about/"}]},{"type":"paragraph","text":"Volatility is the one quantity in technical analysis that can be forecast, at least in part. Not its direction, but its persistence: quiet periods follow quiet periods, and active ones follow active ones. This clustering is one of the most robust findings in financial research."},{"type":"heading","level":2,"id":"bollinger-bands","text":"Bollinger Bands"},{"type":"image","src":"https://alysly.com/img/ta/bollinger-bands.5e070334e764568d2af9ca884ed02ce83a7a146dfa43f517b6e3d608aaded5f5.webp","alt":"Bollinger bands around a moving average, showing a narrow and a wide phase"},{"type":"paragraph","text":"The bands sit two standard deviations above and below the average — their width is volatility, not direction. (1) Narrow bands mark a quiet phase; such compressions tend to resolve into expansion without revealing the direction. (2) Wide bands show a move already under way. Price at the upper band is therefore not \"too expensive\" — in strong trends it rides along it."},{"type":"paragraph","text":"A moving average, usually over 20 periods, plus and minus two standard deviations. The width of the bands is the volatility."},{"type":"paragraph","text":"The most common misuse is the same as with the RSI: a price at the upper band is read as expensive. It is not. In strong trends the price rides along the band. That is the definition of a strong trend, not a reason to sell."},{"type":"paragraph","text":"The usable application is the squeeze: when the bands contract unusually tightly, an expansion becomes more likely. What the squeeze does not tell you is the direction — and that is exactly where most descriptions stop."},{"type":"heading","level":2,"id":"average-true-range","text":"Average True Range"},{"type":"image","src":"https://alysly.com/img/ta/atr.facf718b35221ce845be0a4af992506491179d1f6b2defcc9273740a3eebb23d.webp","alt":"Price series with average true range in the lower panel"},{"type":"paragraph","text":"Average true range measures the typical daily range — pure magnitude, no direction. (1) In the quiet phase it is low, (2) during the sell-off it rises sharply. Practical use: a stop set \"2% below entry\" means a lot when ATR is low and very little when it is high. Sizing stops in ATR units instead keeps risk constant across market regimes."},{"type":"paragraph","text":"The true range of a period is the largest of three distances: high minus low, high minus previous close, and previous close minus low. The two terms with the previous close matter because they account for gaps, which a plain high-minus-low range would ignore. ATR is the average of those values over n periods, by convention 14."},{"type":"paragraph","text":"ATR is not a statement about direction and not a signal. Its value lies in two practical uses:"},{"type":"paragraph","text":"Stops in ATR units. A stop “2 percent below entry” gives plenty of room when volatility is low and almost none when it is high. A stop “two ATR below entry” keeps the distance constant relative to the movement that actually occurs — across instruments and across market regimes."},{"type":"paragraph","text":"Position size. Once the stop is expressed in ATR units, the position size follows directly from the risk formula: risk in currency divided by (ATR × factor). More volatile instruments automatically get smaller positions, so the risk per position stays constant instead of moving with the temperament of the instrument.","links":[{"text":"risk formula","href":"https://alysly.com/learn/risk-and-position-sizing/"}]},{"type":"paragraph","text":"That second use is probably the single most practical building block in this level."},{"type":"heading","level":2,"id":"keltner-channels","text":"Keltner Channels"},{"type":"paragraph","text":"Similar to Bollinger bands, but built around ATR instead of standard deviation. The difference is not cosmetic: standard deviation reacts strongly to single outliers, while ATR reacts more evenly. For stop logic the ATR version is usually the steadier one."},{"type":"heading","level":2,"id":"why-volatility-is-the-more-dependable-quantity","text":"Why Volatility Is the More Dependable Quantity"},{"type":"paragraph","text":"The direction of prices can hardly be forecast. That is the core of the criticism of technical analysis. Volatility can be forecast in part, because it is strongly autocorrelated."},{"type":"paragraph","text":"This is exactly why the practical value of this chapter lies in risk management rather than in signals. You cannot know where the price is going, but you can estimate reasonably well how far it will move over the next week. Turning that estimate into stops and position sizes uses the most reliable part of the entire toolbox."},{"type":"heading","level":2,"id":"next","text":"Next"},{"type":"paragraph","text":"The last article of this level: how to test a pattern or an indicator in the first place."},{"type":"list","ordered":false,"items":[{"text":"Previous MACD and Trend Strength","href":"https://alysly.com/learn/macd-and-trend-strength/"},{"text":"Next Testing a Pattern","href":"https://alysly.com/learn/testing-a-pattern/"}]},{"type":"heading","level":2,"text":"Indices"},{"type":"table","caption":"Indices, performance over the selected period","columns":["Index","1M"],"rows":[[{"text":"Dow Jones","href":"https://alysly.com/markets/indices/dow-jones/"},{"text":"+1.2%","data":{"m1":"+1.2%","m3":"-2.9%","m6":"+4.3%","ytd":"+8.7%","max":"+31.4%"}}],[{"text":"S&P 500","href":"https://alysly.com/markets/indices/sp500/"},{"text":"-2.7%","data":{"m1":"-2.7%","m3":"-2.7%","m6":"+1.2%","ytd":"+11.0%","max":"+36.1%"}}],[{"text":"MSCI World","href":"https://alysly.com/markets/indices/msci-world/"},{"text":"-1.9%","data":{"m1":"-1.9%","m3":"-3.0%","m6":"+1.2%","ytd":"+10.4%","max":"+35.6%"}}],[{"text":"MSCI ACWI","href":"https://alysly.com/markets/indices/msci-acwi/"},{"text":"-2.6%","data":{"m1":"-2.6%","m3":"-3.7%","m6":"-0.1%","ytd":"+10.6%","max":"+42.1%"}}]]},{"type":"heading","level":2,"text":"ETFs"},{"type":"table","caption":"ETFs, performance over the selected period","columns":["Fund","1M"],"rows":[[{"text":"SPDR S&P 500 ETF Trust SPY","links":[{"text":"SPDR S&P 500 ETF Trust","href":"https://alysly.com/markets/etfs/us/spy/"}]},{"text":"-2.7%","data":{"m1":"-2.7%","m3":"-2.7%","m6":"+1.2%","ytd":"+11.0%","max":"+36.1%"}}],[{"text":"Vanguard S&P 500 ETF VOO","links":[{"text":"Vanguard S&P 500 ETF","href":"https://alysly.com/markets/etfs/us/voo/"}]},{"text":"-2.7%","data":{"m1":"-2.7%","m3":"-2.7%","m6":"+1.2%","ytd":"+11.0%","max":"+34.5%"}}],[{"text":"iShares Core MSCI World UCITS ETF USD (Acc) EUNL","links":[{"text":"iShares Core MSCI World UCITS ETF USD (Acc)","href":"https://alysly.com/markets/etfs/ishares-core-msci-world-ucits-etf-usd-acc/"}]},{"text":"-1.8%","data":{"m1":"-1.8%","m3":"-3.0%","m6":"+1.9%","ytd":"+11.1%","max":"+490.2%"}}],[{"text":"Xtrackers MSCI Emerging Markets UCITS ETF 1c XMME","links":[{"text":"Xtrackers MSCI Emerging Markets UCITS ETF 1c","href":"https://alysly.com/markets/etfs/xtrackers-msci-emerging-markets-ucits-etf-1c/"}]},{"text":"-6.3%","data":{"m1":"-6.3%","m3":"-7.8%","m6":"-8.3%","ytd":"+12.6%","max":"+90.7%"}}]]},{"type":"heading","level":2,"text":"Stocks"},{"type":"table","caption":"Stocks, performance over the selected period","columns":["Stock","1M"],"rows":[[{"text":"NVIDIA Corporation NVDA","links":[{"text":"NVIDIA Corporation","href":"https://alysly.com/markets/stocks/nvidia-corporation/"},{"text":"United States","href":"https://alysly.com/markets/stocks/browse/?country=United%20States"}]},{"text":"-27.3%","data":{"m1":"-27.3%","m3":"-26.2%","m6":"-29.5%","ytd":"-10.9%","max":"+30.4%"}}],[{"text":"Apple Inc. AAPL","links":[{"text":"Apple Inc.","href":"https://alysly.com/markets/stocks/apple-inc/"},{"text":"United States","href":"https://alysly.com/markets/stocks/browse/?country=United%20States"}]},{"text":"+4.0%","data":{"m1":"+4.0%","m3":"+16.3%","m6":"+19.0%","ytd":"+30.5%","max":"+55.9%"}}],[{"text":"Tesla Inc. TSLA","links":[{"text":"Tesla Inc.","href":"https://alysly.com/markets/stocks/tesla-inc/"},{"text":"United States","href":"https://alysly.com/markets/stocks/browse/?country=United%20States"}]},{"text":"+5.9%","data":{"m1":"+5.9%","m3":"+16.9%","m6":"-10.3%","ytd":"-11.6%","max":"+64.9%"}}]]},{"type":"paragraph","text":"Data note 1","href":"#dn-1"},{"type":"heading","level":2,"text":"More Research"},{"type":"list","ordered":false,"items":[{"text":"Oct 14, 2025 Trading +227.8% the market itself, 2017–2026, no trading Why Most Traders Lose Money: What the Data Shows The market paid 13.5% a year. Five measurable forces decide how much of that a trader keeps, and at ordinary trading frequencies it is very little.","href":"https://alysly.com/research/why-most-traders-lose-money/"},{"text":"May 19, 2026 Crypto 45.6% Bitcoin’s annualized volatility, Jul 2024 — Sep 2026 Bitcoin in Investment Portfolios: The Real Numbers Bitcoin is calmer than it was and still about three times as volatile as the stock market. It moves with stocks, not with gold.","href":"https://alysly.com/research/bitcoin-investment-portfolios/"},{"text":"Jan 13, 2026 ETFs 73.0% United States share of the MSCI World US Weight in the MSCI World: What Does It Really Mean for Investors? Holding 1,248 companies sounds diversified. Measured by weight, the MSCI World behaves like 85 of them.","href":"https://alysly.com/research/msci-world-us-weight/"}]},{"type":"paragraph","text":"View all research","href":"https://alysly.com/research/"},{"type":"heading","level":2,"text":"Learn"},{"type":"list","ordered":false,"items":[{"text":"Testing a Pattern From shape to testable rule — and the traps along the way.","href":"https://alysly.com/learn/testing-a-pattern/"},{"text":"AI Trading: How It Works and Where It Fails From data to order: how AI trading works, and the hurdle it has to clear.","href":"https://alysly.com/learn/ai-trading/"}]},{"type":"paragraph","text":"Course overview","href":"https://alysly.com/learn/"},{"type":"paragraph","text":"Published Aug 2, 2026 · Updated Nov 4, 2026 · Data checked automatically Nov 13, 2026"},{"type":"heading","level":2,"id":"note-legend-h","text":"Data Notes"},{"type":"paragraph","text":"All calculations run automatically and are not investment advice."},{"type":"list","ordered":true,"items":[{"id":"dn-1","text":"Returns computed automatically from the price series, excluding dividends, taxes and costs."}]},{"type":"paragraph","text":"Data and methodology: Alysly · Responsible for content: Alexander Bock","links":[{"text":"Alysly","href":"https://alysly.com/methodology/"},{"text":"Alexander Bock","href":"https://alysly.com/about/"}]},{"type":"paragraph","text":"View all data notes","href":"https://alysly.com/notes/"}],"structured_data":[{"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://alysly.com/#org","name":"Alysly","url":"https://alysly.com/","logo":{"@type":"ImageObject","url":"https://alysly.com/img/icon-512.png","width":512,"height":512},"description":"Free analysis tools for traders and long-term investors. 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