Line Plot: Definition, How to Read It & Examples

Definitionnoun phrase

What is a line plot in math?

A line plot shows data values along a number line, often with marks above each value. Each X or dot stands for one data value, and repeated values stack in a column, so the tallest stack is the mode. Line plots make it easy to see clusters, gaps, outliers and the spread of a small data set.

In Spanish: diagrama de puntos
Also called: dot plot, X plot, dot diagram
Grade level: K-5

Grade 3Grade 4Grade 5Grade 6CCSS 3.MD.B.4CCSS 5.MD.B.2CCSS 6.SP.B.4GED

Line Plot in a picture

Every X is one leaf, so you can count the data, find the most common length (the tallest stack, 2½ inches) and see the spread at a glance.

Formal definition and notation

A line plot (also called a dot plot) displays a distribution of numerical data by placing one mark (an X or a dot) above a number line at the position of each data value. The number line is marked off in units that fit the data, such as whole numbers, halves or quarters. The number of marks above a value is its frequency, and the total number of marks equals the number of data values. Every individual value stays visible, so the mean, median, mode and range can be read or computed from the plot.

Symbol	Read it as	Meaning
X or •	one mark	one data value; a key may say otherwise, such as X = 2 students
a stack of 4 marks above 212	four at two and a half	the value 212 appears 4 times in the data

Key facts

Each mark is one data value, so the total number of marks is the size of the data set.
The tallest stack is the mode. The distance from the leftmost to the rightmost mark is the range.
To find the median, count marks from the left to the middle one (or the middle two).
Line plots suit small data sets with values that repeat. For many different values spread widely, a histogram is clearer.
In Grades 3 to 5, line plots often show measurements in halves, quarters or eighths of a unit.

How to make a line plot

number line → one mark per value → stack repeats → title and label

number line: cover the smallest to the largest value with equal spacing, including values with no data
one mark per value: cross off each data value as you plot it so none is missed or doubled
stack repeats: put repeated values in a neat column of equal-sized marks
title and label: say what was measured and in which unit

Count the marks at the end. The count must equal the number of data values.

Try it: build a dot plot

Interactive

These are the numbers of books 12 students read in a month. Edit the list, drag a dot, or press Add a value, and watch the stacks grow. The readout gives the count, mode, median and range. Add an outlier and see where it lands.

This interactive needs JavaScript. The worked examples below show the same ideas step by step.

Line Plot examples, step by step

Example 1: Read a line plot

Warm-up

A line plot of quiz scores shows 2 X’s above 6, 3 above 7, 5 above 8, 2 above 9 and 1 above 10. How many students took the quiz, and what is the most common score?

Each X is one student, so add the stacks: 2 + 3 + 5 + 2 + 1.
2 + 3 = 5, 5 + 5 = 10, 10 + 2 = 12, 12 + 1 = 13.
The tallest stack is above 8, with 5 X’s.

Answer: 13 students took the quiz, and the most common score is 8.

Example 2: Fractions on a line plot

Core

A line plot shows the water in 6 beakers: 3 X’s above 14 liter, 2 above 12 liter and 1 above 34 liter. If all the water were shared equally among the 6 beakers, how much would each hold?

Total water: 3 × 14 + 2 × 12 + 1 × 34.
34 + 1 + 34 = 212 liters.
Share among 6 beakers: 212 ÷ 6 = 52 × 16 = 512 liter.

Answer: Each beaker would hold 512 liter.

Example 3: Median and range from a line plot

Test-style

A line plot of hours of sleep shows 2 X’s above 6, 3 above 7, 4 above 8, 1 above 9 and 1 above 12. Find the median and the range. Which one does the value at 12 affect more?

There are 2 + 3 + 4 + 1 + 1 = 11 X’s, so the median is the 6th from the left.
Count: two 6s (1st and 2nd), three 7s (3rd to 5th), so the 6th is the first 8. Median = 8.
Range: 12 − 6 = 6 hours.
The lone 12 stretches the range from 3 to 6 hours but does not change the median.

Answer: Median = 8 hours, range = 6 hours. The value at 12 affects the range much more than the median.

Common mistakes

✗ MistakeDrawing a line plot by connecting the data points with line segments.

✓ InsteadLeave the marks as separate X’s or dots stacked above the number line.

Do not confuse a line plot with a line graph; a line plot shows individual data values. A line graph connects points to show change over time.

✗ MistakeThe line plot has 5 stacks, so there are 5 data values.

✓ InsteadCount every mark: 1 + 2 + 4 + 2 + 1 = 10 data values.

Each stack is a value; each mark in it is one data point. The total is the number of marks.

✗ MistakeThe tallest stack has 4 X’s, so the mode is 4.

✓ InsteadThe mode is the value under the tallest stack, 212 inches. The 4 is how often it occurs.

The height of a stack is a frequency, not a data value. Read the number on the line below it.

✗ MistakeLeaving 5 off the number line because no one read 5 books.

✓ InsteadMark 5 with no X’s above it.

The number line must be evenly spaced. Skipping empty values hides gaps and makes the data look closer together than they are.

Not to be confused with

Line Plotvs.Line graph

A line graph plots points over time and connects them with line segments, such as daily temperatures. A line plot stacks marks above a number line to count how often each value occurs.

Line Plotvs.Histogram

A histogram groups values into intervals and draws a bar for each, so single values disappear. A line plot keeps every value as its own mark.

Line Plotvs.Bar Graph

A bar graph compares categories, such as favorite sports. A line plot uses a number line, so its values are numbers in order.

Quick check: 3 questions

Question 1 of 3

On a line plot of pets per family, there are 3 X’s above the 2. What does that mean?

Show answer and explanation

Answer: B. The number on the line is the value (2 pets) and each X is one family, so 3 families have 2 pets. Choice A swaps the value and the count, and choice D reads the stack height as the mode.

Question 2 of 3

A line plot has 2 X’s above 1, 4 above 2, 1 above 3 and 3 above 4. How many data values are greater than 2?

Show answer and explanation

Answer: A. Values greater than 2 are the X’s above 3 and 4: 1 + 3 = 4. 7 includes the X’s at 2, and 2 counts stacks instead of marks.

Question 3 of 3

For the same line plot (2 X’s at 1, 4 at 2, 1 at 3, 3 at 4), what is the mode?

Show answer and explanation

Answer: C. The tallest stack, 4 X’s, is above the value 2, so the mode is 2. Choice A confuses the height of the stack (4) with the value, and 4 is also the largest value, not the most common.

Line Plot: frequently asked questions

Is a line plot the same as a dot plot?

Yes. The Common Core glossary defines a line plot as a way to display data values on a number line and says it is also known as a dot plot. Some books use X’s and call it a line plot; others use dots and call it a dot plot. Either way, each mark is one data value above its place on the number line.

What is the difference between a line plot and a line graph?

A line plot shows how often each value occurs, with marks stacked above a number line. A line graph shows how something changes, usually over time, with points joined by line segments. Use a line plot for the heights of 15 plants; use a line graph for one plant’s height measured every week.

How do you find the mean from a line plot?

Multiply each value by the number of marks above it, add the results, and divide by the total number of marks. For 2 X’s at 3, 1 at 4 and 2 at 6: 2 × 3 + 1 × 4 + 2 × 6 = 22, and 22 ÷ 5 = 4.4. The median and mode can be read straight from the stacks.

Practice and tools

Math practicePractice on Effortless Math Descriptive Statistics CalculatorMean, median, mode and range of your line-plot data Stem-and-Leaf Plot MakerAnother display that keeps every value visible

Sources

Updated November 2026·Reviewed by the Effortless Math team·Standards: CCSS 3.MD.B.4, CCSS 5.MD.B.2, CCSS 6.SP.B.4

Cite this entry

Effortless Math Team. “Line Plot.” Effortless Math Dictionary. Updated November 2026. https://www.effortlessmath.com/math-dictionary/line-plot/

Flashcard

TermLine PlotX’s stacked above a number line

DefinitionA display with one mark above a number line for each data value; repeats stack up. Three X’s above 5 means 5 occurs three times.

Study the full deck

Browse all terms in the Math Dictionary · More statistics terms · Random term

Dot PlotA dot plot is a graph that shows each data value as a dot above its place on a number line. Dots for repeated values stack up in a column, so the tallest stack shows the mode, and you can see the center, spread, gaps and outliers of the data at a glance.Statistics · Grade 3, Grade 4, Grade 5DataData are facts or values collected to answer a question, such as survey answers, measurements or counts. Numerical data are numbers you measure or count, like heights; categorical data are labels or groups, like favorite colors. Data are organized in tables and shown in graphs so patterns are easy to see.Statistics · Grade 2, Grade 3, Grade 6Number LineA number line is a straight line with numbers placed at equal distances along it, so every point stands for a number. Zero sits in the middle, positive numbers go to the right and negative numbers to the left. Numbers increase from left to right, so a number line shows order, distance and adding as moving.Number System · Grade 2, Grade 3, Grade 6Whole NumberA whole number is 0 or a positive counting number: 0, 1, 2, 3, and so on. Whole numbers do not include fractions, decimals, or negative numbers, so 12 is a whole number but 8.5, 34 and −3 are not. Every whole number is also an integer.Number System · Grade 3, Grade 4, Grade 5NumberA number is an amount or value used to count, measure, order and compare. We write numbers with digits (7), words (seven) or other symbols, but the number itself is the amount: 7 dots, the word seven and the numeral 7 all show the same number. Numbers include whole numbers, fractions, decimals and negatives.Number System · Kindergarten, Grade 1, Grade 2MedianThe median is the middle value when data are listed in order. If there is an even number of values, the median is the average of the two middle values. Half the data lie at or below the median and half at or above it, and outliers barely move it.Statistics · Grade 5, Grade 6, Grade 7ModeThe mode is the value that appears most often in a data set. To find it, count how many times each value occurs and pick the most frequent one. A data set can have one mode, more than one mode, or no mode at all when every value appears only once. The mode works for categories, too.Statistics · Grade 5, Grade 6, Grade 7RangeThe range of a data set is the difference between the greatest and least values: maximum minus minimum. For 2, 5, 9, the range is 9 − 2 = 7. Range is a simple measure of spread: it tells how far apart the extreme values are, though one outlier can make it misleading about the rest of the data.Statistics · Grade 5, Grade 6, Grade 7HistogramA histogram uses bars to show how numerical data are grouped into intervals. The data are split into equal-width intervals, called bins, and each bar’s height is the count of values in that interval. The bars touch, because the intervals are continuous, which is what distinguishes a histogram from a bar graph.Statistics · Grade 6, Grade 7, Grade 8Line SegmentA line segment is a straight part of a line with two endpoints. It starts at one point, stops at another, and includes every point between them. A segment with endpoints A and B is written AB. Unlike a line, which goes on forever, a segment has a definite length that you can measure.Geometry · Grade 4, Grade 5, Grade 6InchAn inch is a US customary unit of length equal to one twelfth of a foot, about the width of an adult thumb. Its abbreviation is in. Rulers split each inch into halves, quarters, eighths and sixteenths. One inch is exactly 2.54 centimeters, and 12 inches make 1 foot.Measurement · Grade 2, Grade 3, Grade 4HeightHeight is how tall something is: the distance from its bottom to its top, measured straight up and down. In geometry, the height of a shape is the perpendicular distance from a base to the opposite vertex or side, so it always meets the base at a right angle. Area and volume formulas use it.Measurement · Grade 2, Grade 5, Grade 6Bar GraphA bar graph uses bars to compare amounts in different categories. The taller or longer the bar, the larger the value it represents. Each bar stands for one category, such as a favorite sport, and its length is read against a number scale. Bars can be vertical or horizontal, with gaps between them.Statistics · Grade 3, Grade 4, Grade 5MeanThe mean is the sum of the values divided by the number of values. It is the arithmetic average: add every value and divide by how many there are. For 3, 7, 5 and 9, the mean is 24 ÷ 4 = 6. The mean is the balance point of the data, so one outlier can pull it far.Statistics · Grade 5, Grade 6, Grade 7OutlierAn outlier is a data value that is far away from most of the other values in a set. In 4, 5, 6, 7, 50, the value 50 is an outlier. A common test flags any value more than 1.5 times the interquartile range below the first quartile or above the third. Outliers pull the mean strongly.Statistics · Grade 6, Grade 7, Grade 8Box PlotA box plot displays a data set through five numbers: minimum, first quartile, median, third quartile, and maximum. The box holds the middle half of the data, a line inside it marks the median, and whiskers reach out to the smallest and largest values. It makes spread easy to compare between sets.Statistics · Grade 6, Grade 7, Grade 8

Line Plot

What is a line plot in math?

Line Plot in a picture

Formal definition and notation

Key facts

How to make a line plot

Try it: build a dot plot

Line Plot examples, step by step

Example 1: Read a line plot

Example 2: Fractions on a line plot

Example 3: Median and range from a line plot

Common mistakes

Not to be confused with

Quick check: 3 questions

Line Plot: frequently asked questions

Is a line plot the same as a dot plot?

What is the difference between a line plot and a line graph?

How do you find the mean from a line plot?

Related terms

Practice and tools

Sources

Flashcard

Login

Login and use all of our services.

Register

Register Fast!

Choose your next math review topic