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What are Bollinger Bands?

Highlighted from a real earnings story. Explained by Clicked.

Used in a sentence

Price hugged the upper Bollinger Band all week as volatility compressed to multi-month lows.

The reader highlighted one word mid-article. Clicked explained the trading term “Bollinger Band” in simple terms:

Explained in three depths

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Overview

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Bollinger Bands are three lines around a price chart: a 20-day average in the middle, plus bands set two standard deviations above and below it. The bands widen when prices have been swinging hard and tighten when trading is quiet — a live, self-adjusting map of the stock's volatility.

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Detail

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The middle line is a 20-day moving average of closing prices, redrawn daily as the window slides forward. The bands are set by the standard deviation of those same 20 days — a number that grows when daily prices land far from their average and shrinks when they hug it. With the usual bell-shaped spread of prices, roughly 95% of trading stays inside the bands, so a touch of either band marks a genuinely unusual distance from the average. Because the deviation is recomputed daily, the bands breathe: calm markets squeeze them tight, wild markets balloon them out. Traders read two things from that. A touch of a band is a prompt to look closer, not an automatic buy or sell — strong trends can ride a band for weeks. And a tight squeeze after a quiet stretch often precedes a big move, since volatility tends to alternate between sleep and eruption.

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Analogy

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Quality control on a production line: engineers weigh every 50th cereal box and use weeks of history to set control limits around the target weight. Boxes vary inside the limits all day — the machine's ordinary wobble, nobody touches anything — while a box landing outside them is a signal to stop and inspect, because that gap exceeds the normal noise. Bollinger Bands are those control limits, drawn around a price instead of a box weight.

AI explanations may contain errors · Not professional advice

Same facts, different vibe — Slang mode 😎

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Overview

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Bollinger Bands are the price's personal-space bubble, auto-sized by how wild it's been lately. Calm stock: tight bubble. Chaotic stock: wide bubble — and price touching the edge means it's unusually far from home, which is information, not an order. 😎

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Detail

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The recipe: a 20-day average in the middle, plus bands two standard deviations out — where standard deviation is just a number that gets big when daily moves are big and messy, small when they're sleepy. By construction, about 95% of the action stays inside, so a band touch means "genuinely far from home," statistically speaking. The bands breathe with the market: quiet weeks squeeze them into a corridor, chaos balloons them wide. Rookie trap number one: "it touched the top band, SELL" — no, strong stocks surf the upper band for weeks, and that's what a healthy trend looks like. Rookie trap number two: ignoring the squeeze — a long tight pinch is the market holding its breath, and volatility tends to come out of it swinging. Touches start investigations, not trades. 😎

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Analogy

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It's the risk dashboard at work: someone pulled the historical stats, drew "normal" boundaries around them, and set alerts. When a number crosses a boundary, nobody smashes a big red button — it gets flagged for a human to review, because "unusual" and "wrong" are different words. Bollinger Bands are that dashboard, drawn directly on the price.

AI explanations may contain errors · Not professional advice

Formal definition — The same term, explained the usual way

Bollinger Bands comprise a 20-period simple moving average bounded by bands placed two standard deviations of price above and below, such that band width varies directly with realized volatility. Price interaction with the bands is interpreted contextually: band touches indicate statistically extended prices rather than discrete signals, sustained contact accompanies trending conditions, and pronounced band contraction — the squeeze — is monitored as a precursor to volatility expansion of indeterminate direction. The construction self-calibrates to each instrument's volatility regime.

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