How to Read and Create Stem-and-Leaf Plots

Stem-and-leaf plots are one of the first statistical displays students learn in the Australian Curriculum, and they are more useful than they might first appear. Unlike bar charts or pie charts, stem-and-leaf plots let you see every single data value while still showing the overall shape of the data. That makes them a favourite in Year 7 and Year 8 maths, and they turn up regularly in tests and exams.

This guide walks through how to read them, how to create them from raw data, and how to pull out the key statistics that exam questions love to ask about.

What is a stem-and-leaf plot?

A stem-and-leaf plot splits each number in a data set into two parts: the stem (usually the leading digit or digits) and the leaf (usually the last digit). The stems go in a column on the left, and the leaves are written in a row to the right of their stem, in order from smallest to largest.

For example, the number 37 has a stem of 3 and a leaf of 7. The number 85 has a stem of 8 and a leaf of 5.

Here is a finished stem-and-leaf plot showing test scores out of 100 for a class of 15 students:

Stem	Leaf
4	3 8
5	2 5 7
6	1 4 4 6
7	0 3 8
8	2 5
9	1

Key: 4 | 3 means 43

Every stem-and-leaf plot needs a key. Without it, readers cannot tell whether 4 | 3 means 43, 4.3, or 430. Always include one.

How to create a stem-and-leaf plot from scratch

Suppose you are given these 12 values representing the ages of people at a family gathering:

8, 12, 35, 42, 7, 15, 38, 41, 12, 55, 29, 33

Step 1: Order the data

Sort the values from smallest to largest: 7, 8, 12, 12, 15, 29, 33, 35, 38, 41, 42, 55.

Step 2: Identify the stems

The data ranges from 7 to 55, so the stems will be the tens digits: 0, 1, 2, 3, 4, 5. Single-digit numbers like 7 and 8 have a stem of 0.

Step 3: Write the stems in a column

List every stem from smallest to largest, even if a stem has no leaves. Do not skip stems.

Step 4: Add the leaves

Write each leaf next to its stem, in order. The finished plot looks like this:

Stem	Leaf
0	7 8
1	2 2 5
2	9
3	3 5 8
4	1 2
5	5

Key: 1 | 2 means 12

Reading information from a stem-and-leaf plot

Once you have a plot, you can quickly find important statistics without going back to the raw data.

Finding the range

The range is the largest value minus the smallest. From the test score plot above: 91 minus 43 = 48.

Finding the median

Count the total number of leaves (that is the total number of data values). For 15 values, the median is the 8th value when listed in order. Read across the leaves from smallest to largest: 43, 48, 52, 55, 57, 61, 64, 64, 66, 70, 73, 78, 82, 85, 91. The median is 64.

Finding the mode

Look for the leaf that appears most often on the same stem. In the test score plot, the leaf 4 appears twice on stem 6 (both representing 64), making 64 the mode.

Common mistakes to avoid

Forgetting to sort the leaves. Leaves must be in ascending order on each row. If they are not sorted, the plot is wrong and finding the median becomes unreliable.
Skipping stems with no data. If no values fall in the 20s but there are values in the 10s and 30s, you still write the stem 2 with no leaves. This keeps the shape of the data accurate.
Missing the key. Without a key, the plot is meaningless. Marks are almost always deducted for this in assessments.
Confusing stem and leaf direction. The stem is the leading digit. For two-digit numbers, the tens digit is the stem and the units digit is the leaf.

Back-to-back stem-and-leaf plots

In Year 8 and beyond, you will often see back-to-back stem-and-leaf plots that compare two data sets. The stems sit in the middle column, with one set of leaves going to the right and the other going to the left (reading outward from the stem). These are useful for comparing the spread and centre of two groups, such as test results from two different classes.

Why stem-and-leaf plots matter

They might seem old-fashioned compared to fancy digital charts, but stem-and-leaf plots are genuinely useful for small data sets because they preserve every data point. You can read off the exact values, find the median quickly, and see the distribution at a glance. That is why they remain a staple of the Australian Curriculum through to Year 10.

If your child is working through statistics topics and finding data displays tricky, imSteyn covers stem-and-leaf plots as part of the Year 7 and Year 8 statistics units. It walks students through creating and interpreting plots step by step, asking guiding questions rather than giving away the answers. You can try it free and see if the approach works for your child.

Quick reference checklist

Sort the data from smallest to largest.
Identify the stems (leading digits) and list them in a column.
Write each leaf (last digit) next to its stem, in order.
Include a key (e.g. 3 | 5 means 35).
Do not skip empty stems.

Get those five things right and you will not go wrong with stem-and-leaf plots.