Understanding a Stock Chart

A stock chart is a visual representation of trading information over a selected period.

Price is normally displayed vertically, and time is displayed horizontally. Everything else on the chart—bars, candles, lines, and indicators—is organized around those two axes.

Before interpreting any chart, a researcher should first be able to explain what the chart is displaying.

Every completed point, bar, or candle on a chart represents market activity that has already occurred.

A stock chart records historical market behavior; it does not guarantee future price behavior.

This is the single most important principle in chart reading. The chart is a record, not a forecast.

A stock chart is built from two main axes:

• Vertical axis = price
• Horizontal axis = time

Reading a chart always begins with these two axes: what price is being shown, and over what period of time.

Price
  ↑
  |
  |
  |
  +----------------→ Time

The vertical axis displays price levels.

The visible price range changes depending on the stock, the time period displayed, and the chart settings. A stock trading near $10 and a stock trading near $1,000 will display very different price scales.

The horizontal axis organizes trading activity chronologically, from earlier activity on the left to more recent activity on the right.

Depending on the chart, the time axis may display:

• minutes
• hours
• days
• weeks
• months
• years

These two ideas are often confused, so the distinction should be made very clear:

Chart range is how much history is displayed on the chart.

Timeframe or interval is how much trading activity each bar or candle represents.

Example: a one-year chart range combined with a daily timeframe displays approximately one year of history using daily bars or candles.

A one-year chart can still use daily candles or weekly candles.

Changing the interval changes how the same history is summarized. Daily candles divide that year into roughly 250 trading sessions; weekly candles compress the same year into roughly 52 candles.

The history is the same. The level of summarization is different.

Common chart ranges include:

• 1 month
• 3 months
• 6 months
• 1 year
• 5 years
• maximum available history

No single chart range is universally best. The appropriate range depends on the research question being asked.

A shorter range provides more detail about recent activity.

A longer range provides more historical context.

Neither is automatically better. A researcher studying a recent decline may need both: a shorter range for recent detail and a longer range to understand where the current price sits within the stock's history.

Common chart intervals include:

• 1 minute
• 5 minute
• 15 minute
• hourly
• daily
• weekly
• monthly

This course will primarily emphasize daily charts for general stock research while explaining other intervals where relevant.

Daily charts provide a practical balance between recent price detail and longer-term context.

Each candle summarizes one complete trading session, so a one-year daily chart displays a full year of sessions at a readable level of detail.

This does not mean daily charts are inherently superior for all purposes. They are simply a practical starting point for the kind of research this course teaches.

Intraday charts divide a trading day into shorter intervals.

Examples include 1-minute, 5-minute, 15-minute, and hourly intervals.

Intraday charts contain more short-term fluctuations and are not necessary for every long-term research question.

A weekly bar or candle summarizes trading activity over an entire week.

Weekly charts can help researchers view longer-term behavior with less daily detail, smoothing out some of the short-term noise visible on a daily chart.

Monthly charts compress even more information, with each bar or candle representing an entire month of trading.

They can provide long-term historical perspective—useful for understanding where the current price sits relative to many years of history.

A line chart commonly connects one selected price—often closing prices—over time.

Line charts are simple to read but discard most of the information within each interval.

Not every platform constructs line charts identically; some allow the connected price to be changed.

Bar charts can display four prices for each interval:

• Open
• High
• Low
• Close

These four values are commonly abbreviated as OHLC. Bar charts present them using vertical lines with small horizontal marks.

Candlestick charts also summarize the open, high, low, and close for each interval, presenting them in a visual format that many researchers find easier to scan.

Lesson 2 will examine candlesticks in detail.

Each chart type presents trading information differently. None of them is universally best; the choice depends on what the researcher wants to see.

The open is the first traded price represented for the selected interval, according to the chart or data convention being used.

For a daily candle, the open is generally the first traded price of that trading session.

The high is the highest traded price represented during the selected interval.

It marks the upper boundary of trading activity for that period.

The low is the lowest traded price represented during the selected interval.

It marks the lower boundary of trading activity for that period.

The close is the final traded price represented for the selected interval, according to the applicable market or data convention.

The close is commonly used in chart calculations because it represents the last agreed price of a completed interval—the point at which the market's trading for that period settled.

Consider one interval with the following values:

• Open = $50 — the first traded price of the interval
• High = $54 — the highest traded price during the interval
• Low = $49 — the lowest traded price during the interval
• Close = $53 — the final traded price of the interval

These four numbers completely describe the trading range and direction of that single interval. They do not, by themselves, predict what the next interval will do.

Price change measures the difference between two prices:

Price Change = Current Price − Previous Price

Example: Previous close = $50, Current close = $53.

Price Change = $53 − $50 = $3.

Percentage change expresses the same movement relative to the starting price:

Percentage Change = (Current Price − Previous Price) ÷ Previous Price × 100

Example: Previous close = $50, Current close = $53.

($53 − $50) ÷ $50 × 100 = 6%.

Percentage change makes it possible to compare movements between stocks trading at very different price levels.

Charts may use different price-scale settings, which change how price movement is displayed vertically.

The two most common settings are the linear scale and the logarithmic scale.

This is an introductory overview; the important point is to know which scale the chart is using.

On a linear scale, equal vertical distances represent equal dollar changes.

Example: a move from $10 to $20 is a $10 change, and a move from $100 to $110 is also a $10 change. On a linear scale, both moves occupy the same vertical distance—even though the first is a 100% gain and the second is a 10% gain.

A logarithmic scale emphasizes proportional or percentage changes rather than equal dollar changes.

On a logarithmic scale, the move from $10 to $20 would occupy much more vertical distance than the move from $100 to $110, because the first is the larger percentage change.

Students are not required to use one scale exclusively. The key is to recognize which scale a chart is using before interpreting the visual size of a move.

Historical chart data may be adjusted for corporate actions such as stock splits and, depending on the data source and settings, dividends.

Always understand what the charting platform means by “adjusted” before comparing historical prices.

Example: a 2-for-1 stock split changes one $100 share into two $50 shares, ignoring other market movement.

The shareholder owns the same total value before and after the split—two shares at $50 equal one share at $100.

On an unadjusted historical chart, the split could appear to show a sudden 50% collapse, even though the split itself did not create that economic loss. Adjusted charts restate earlier prices so the history remains comparable.

A gap is an area where price moves between trading periods without trading through all the intervening prices on the displayed chart.

For example, a stock might close one session at $50 and open the next session at $53, leaving the prices between $50 and $53 untraded on a daily chart.

This lesson introduces gaps as a chart feature only; it does not teach gap-trading strategies.

Stock trading occurs in different sessions:

• Regular trading hours — the primary session when the exchange is fully open
• Pre-market — trading that occurs before the regular session
• After-hours — trading that occurs after the regular session closes

Chart appearance can differ depending on whether extended-hours data is included. Two charts of the same stock can look different simply because one includes pre-market and after-hours prices and the other does not.

Small differences may occur among chart providers because of differences in:

• data feeds
• adjustments
• extended-hours settings
• calculation conventions
• timing

Do not automatically assume one chart is wrong because of a small difference. Check the settings and conventions before comparing charts from different platforms.

When viewing a chart during market hours, the most recent candle may represent an interval that is not yet complete.

Today's high can rise, today's low can fall, and the close is not final until the relevant session closes.

A completed historical candle is a fixed record of that completed interval, subject to legitimate later data corrections or adjustments.

The current candle is still developing. Its open is set, but its high, low, and close can all change until the interval ends.

This distinction becomes important when interpreting charts during market hours: observations based on an unfinished candle describe a moment in progress, not a completed record.

Indicators are calculations or additional data layered onto the underlying price history.

Examples include moving averages, volume, RSI, and stochastic indicators.

Price itself should not be confused with an indicator. The price history is the underlying record; indicators are derived from it or added alongside it.

Adding many indicators can make a chart harder to understand rather than easier.

This course builds chart knowledge progressively: price first, then volume, trends, support and resistance, moving averages, and later combined analysis.

A researcher who understands price well will gain more from each additional layer than one who stacks indicators without understanding the underlying chart.

A stock chart can help a researcher observe several things about historical market activity. Each observation has limits—the chart shows what happened, not what must happen next.

Just as important as what a chart shows is what it cannot show. The following box lists conclusions that a chart alone cannot establish.

Before interpreting trends, support, resistance, or indicators, work through a structured process for understanding what the chart in front of you actually displays.

The following process and checklist turn this lesson into a repeatable routine.

1. 1Identify the stock or security.
2. 2Check the current date and market status.
3. 3Identify the chart range.
4. 4Identify the timeframe or interval.
5. 5Identify the chart type.
6. 6Read the price axis.
7. 7Read the time axis.
8. 8Identify the most recent completed interval.
9. 9Distinguish completed data from the current developing interval.
10. 10Note the visible historical highs and lows.
11. 11Record observations without turning them into predictions.
12. 12Decide what additional research is needed.