Line Graph Examples and How to Read Them

The best way to learn a chart is to read a few. These line graph examples for students and beginners start with the simplest possible line and add one idea at a time: markers, curves, shading, a zoomed axis and a second line. Each example has a chart, a note on what to look at and one question with its answer. After the examples you will find a step-by-step method for describing any line graph, an honest answer on whether the axis must start at zero, and a short list of cases where a line is the wrong chart.

What Is a Line Graph?

A line graph shows how a value changes across an ordered scale, most often time. According to Wikipedia, a line chart (the same thing) displays information as a series of data points called markers, connected by straight line segments. It is similar to a scatter plot, except that the points are ordered, usually by their x-axis value, and joined. Claus Wilke’s open textbook Fundamentals of Data Visualization says the same in other words: when each point has a defined order, connecting neighboring points with lines emphasizes that order, and the result is called a line graph.

That is why a line graph is good at answering questions about change: did the value go up, by how much, and when did it turn?

The Parts of a Line Graph

Every line graph is built from the same pieces. Learn to name them and you can read any chart.

• Title. Says what is measured and when.
• Horizontal axis (x-axis). The ordered scale, such as months or weeks.
• Vertical axis (y-axis). The measurement, with a label and a unit.
• Scale. The numbers along the vertical axis, spaced at equal steps.
• Points or markers. One dot for each measured value.
• Line. The segments that join the points in order.
• Legend. Only needed when there are two or more lines, so the reader can match each color to its data set.

The Line Is a Guide, Not Data

Here is a detail that many guides skip. Wilke points out that the lines in a line graph do not represent data. They are only meant as a guide to the eye. The measured values are the points, and everything between two points is an assumption. Keep that in mind, because it matters in Example 4.

Line Graph vs Line Plot

The two names sound alike, but they are different charts. In US grade school math, a line plot shows measurement data above a horizontal scale. The Common Core standards for grade 3 ask students to show the data by making a line plot, where the horizontal scale is marked off in units such as whole numbers, halves or quarters. We did not find a source that defines the term more tightly than that, but the idea is a scale of measurements, not a line joining values over time. So if a worksheet asks for a line plot, check whether it means the grade school kind before you reach for a line graph.

Seven Line Graph Examples to Practice On

All the numbers below are sample data made up for teaching. Each chart has a “Show the data” table under it and an “Open in the tool” button, so you can change the numbers and see what happens.

Example 1: A Simple Line Graph, Rising

The simplest line graph has one line. This one tracks a savings balance at the end of each month.

What to notice:

• One line means no legend is needed.
• The line rises steadily, so the balance grew every month.
• The slope is nearly constant, so the balance grew by about the same amount each month.

Question: how much did the balance grow from January to June? In January it was 150 dollars and in June 1,050 dollars, so it grew by 900 dollars.

Example 2: A Line That Rises and Falls

Most real data goes up and down. This chart shows how many people visit a sample town park each month.

What to notice:

• The line peaks in July at 1,620 visits.
• It dips to its lowest points in January and December, at 300 and 310 visits.
• The climb from February to July and the fall from July to December each cover about 1,300 visits, so the season is almost symmetrical.

Question: in how many months did the park get more than 1,000 visits? Four: May, June, July and August. September is just under, at 980.

Example 3: Markers on a Few Points

With only a handful of measurements, markers (the dots) are worth keeping. They show where the real readings are.

Wilke notes that the denser a time series is, the less important it is to show individual observations with dots. The reverse is also true. With six points, each dot is a fact, and the line between them is only a guide. In our tool this is the Point markers switch. It is on by default, and you may want it off for long series.

Question: which hour had the biggest jump, and how big was it? From 10 am to 11 am, the temperature rose from 62 to 68 degrees, a jump of 6.

Example 4: Straight Segments vs Smooth Curves

Here are the same six readings with the Smooth curves switch turned on.

Look at the line between 10 am and 11 am. Straight segments show a sudden climb. The smooth curve shows a gradual S-shape, which looks natural and says something we never measured. Our tool’s smooth curves stay between neighboring values and never overshoot a point, so they do not invent a higher peak. They can still suggest a pattern of change between two readings that we do not have. That warning is our own editorial caution, not a rule from a textbook.

Question: was the room ever exactly 65 degrees? We cannot tell. The line passes through 65 between 10 am and 11 am, but no one took a reading at that moment. Only the dots are measurements.

When to smooth: for a soft look on a presentation slide, or a long series with many points. When not to: for a few points, or when you want readers to see the exact readings.

Example 5: Area Fill

Shading under the line turns it into an area chart. In our tool this is Shade under lines.

The shading emphasizes the overall trend, because it separates the area above the curve from the area below. Wilke adds a condition: this visualization is only valid if the y-axis starts at zero, so that the height of the shaded area at each point represents the data value. That is why this example also uses Start axis at zero.

What to notice: the list grew from 4,000 to 4,420, a rise of 420, or 10.5 percent. The filled area is large and the growth is gentle.

Question: did the number of subscribers ever fall? No. The area only gets taller from month to month.

Example 6: The Same Data, Zoomed In

Now the same subscriber numbers again, with Start axis at zero switched off and no shading.

Same data, very different feeling. Compare the two charts. From zero, growth of 10.5 percent looks calm. Zoomed in, the line rises across most of the chart and looks like a surge. Neither chart is wrong, because the numbers on the axis are honest, but they send different messages. If you zoom in, say so in the subtitle, as this chart does, and read the axis before the slope.

Question: what should you check first on a zoomed-in graph? The numbers on the vertical axis. The first tick tells you whether the axis starts at zero or somewhere higher.

Example 7: Two Lines on One Grid

One more step: put two data sets on the same axes and the line graph becomes a comparison.

Two lines on one grid let you compare which is higher, how far apart they are and where they cross. Here, Maya starts 10 points behind Leo in week 1 and finishes 4 points ahead in week 6. Gaps, crossings and the common mistakes of two-line charts have their own guide: how to read a double line graph.

How to Read and Describe a Line Graph

You can describe any line graph in about a minute if you follow the same order.

Six Steps to Read a Line Graph

1. Read the title. What is measured, and over what period?
2. Read both axis labels and the units. Then check the vertical scale. Does it start at zero?
3. Find the highest and lowest points. Note the values and where they occur.
4. Follow the line from left to right. Does it rise, fall, stay flat or change direction?
5. Look at the steepness. A steep segment means a fast change. A flat segment means little change.
6. Use the numbers. Read two or three values off the axis or the data table and state the change. “It rose from 4,000 to 4,420” is stronger than “it went up a lot”.

Trend Words to Use

Good descriptions use precise verbs. These are the common ones.

• Rises or increases: the line goes up.
• Falls or decreases: the line goes down.
• Levels off or plateaus: the line goes flat after rising or falling.
• Peaks: the highest point, before the line falls.
• Dips or bottoms out: the lowest point, before the line rises.
• Fluctuates: the line goes up and down with no clear direction.

Add an adverb for speed, such as sharply, steadily or slightly, and a time frame: “between April and July”.

A Model Description

Here is a description of Example 2, with each sentence doing one job.

“The graph shows monthly visits to a town park over one year. Visits rise from 300 in January to a peak of 1,620 in July, then fall back to 310 in December. The steepest single rise is from May to June, up 350 visits, and the park has more than 1,000 visits in four months.”

The first sentence names the topic. The second gives the trend with two numbers. The third adds a detail. That structure works for any line graph, whether you are answering a homework question or writing a report.

Does the Vertical Axis Have to Start at Zero?

Readers ask this all the time, and the honest answer is that the textbook rule is narrower than most people think.

What We Found in Wilke’s Textbook

Wilke’s chapter on the principle of proportional ink is clear about bars: bars on a linear scale should always start at 0. It is also clear about shaded areas under a line, as we saw in Example 5. About a plain line, though, it makes no blanket rule. It discusses a stock price line whose axis started at 110 dollars instead of 0, and says the range would be questionable even without the shading. That is a warning about one chart, not a law.

So we did not find a textbook rule that a line graph, without shading, must start at zero. What we did find is a clear rule for bars and for shaded areas.

Our Advice

This part is our own judgment, not a finding from a source. In a line graph, the message lives in the slope, so a zoomed-in axis can be a fair choice when the changes are small but meaningful, such as body temperature or a test average. Start at zero when the size of the values matters, when you add shading, or when you are not sure and the audience is not expert. In all cases, show the axis numbers and say if the range is zoomed. Our tool has a Start axis at zero switch for exactly this choice.

When a Line Graph Is the Wrong Choice

A line implies that the space between two points means something. If it does not, choose another chart.

Categories With No Order

Take the sample votes for five school lunches. Here they are drawn as a line.

The line makes a story: votes rise and fall. But the order of the lunches is only alphabetical. Rename them or shuffle them and the shape changes, though the votes do not. Wilke says line graphs suit data that has a natural order along x. Lunches do not.

Line Graph vs Bar Graph

The same votes as a bar chart fix the problem.

Each bar stands alone, and you compare heights. Wikipedia describes a bar chart as categorical data with bars whose lengths are proportional to the values, and categories with no natural order can be arranged in any order. Use lines for ordered data such as time, and bars for separate categories. More on reading bars is in our guide to bar graph examples, and you can build your own in the bar graph maker.

Very Few Points

Two or three points make a line graph with almost nothing to read: one segment, or two. A short sentence, a table or a pair of bars usually does the job better. This is our rule of thumb, not a published limit. If you have a handful of points and the order matters, keep the markers on so the reader sees how few there are.

Parts of a Whole

A line graph does not show how a total splits into shares. Use a pie chart, or a stacked bar, when the parts add up to a whole. Our guide to types of graphs and charts has a chooser table for these cases.

A Trend Line Is Not a Line Graph

A line graph joins the actual points in order. A line of best fit is a different thing: a single straight line drawn through scattered points to show a relationship. If that is what you need, see our guide to the line of best fit.

Are There Three Types of Line Graphs?

You may see “three types of line graphs” in worksheets. We found no official list of types in a standard or a textbook, so treat any list as a teaching convention. The names commonly used in school materials are the simple line graph (one line), the multiple line graph (several lines on one grid, with the two-line case called a double line graph) and the compound line graph. We could not verify the last name, and the exact definitions differ between materials. What matters in practice is one line or many, and whether the axis is honest.

Wilke’s textbook describes multiple time series and dose-response curves under the same heading, without the school names.

Start From a Ready-Made Line Graph

You do not need a blank grid. Our template gallery has eight sample line graphs, and you can filter them by business, school and science, or personal use. Examples include a monthly temperature chart, a plant growth experiment, a savings balance and a town’s population over time. Every number in them is sample data. Click “Use this template” to open one in the tool with its data filled in, or download it as a PNG or SVG straight from the card.

If you would rather start from something plain, this starter has one line and five weeks. Type over the labels and values, or paste a table from a spreadsheet.

Open a plain starter in the line graph maker

In the line graph maker, each series column becomes a line, and the switches shown in this guide are all there: Smooth curves, Point markers, Shade under lines and Start axis at zero. If a value is missing, leave its cell empty. The line breaks at that point instead of dropping to zero. You can download a PNG or SVG or copy a link to your chart. It runs in your browser.

A Short History Note

Stephen Few writes that William Playfair did not invent the line graph, but popularized it as a means to display quantitative values across time. Wikipedia lists Playfair, Francis Hauksbee, Nicolaus Samuel Cruquius and Johann Heinrich Lambert among the earliest known users of line charts.

Summary

A line graph joins ordered points to show change, most often over time. Read the title and axes first, find the peaks and dips, follow the line, and describe the trend with numbers. Keep in mind that the points are the measurements and the line is a guide. Turn on markers when there are few points, use smoothing with care, shade only when the axis starts at zero, and say when the axis is zoomed. Choose bars when the categories have no order. Now that you have seen the line graph examples, try your own numbers in the line graph maker.