A stem and leaf plot splits each number into a stem (every digit but the last) and a leaf (the last digit), lists the stems once in order, and writes each value's leaf beside its stem — so 74 becomes 7 | 4. Paste your numbers into this stem and leaf plot generator to get the plot with a key, split stems, decimals and negative values, or a back-to-back plot comparing two groups, plus the count, minimum, quartiles, median, mode, range and mean.
The plot is a stem plot creator and a summary in one: the median and quartiles are calculated exactly as in the box plot maker, so you can draw both charts from the same data and get matching numbers.
How to use the stem and leaf plot maker
- Paste or type your data. Commas, spaces and line breaks all work, so a spreadsheet column pastes straight in.
- Leave the leaf unit on Automatic, or pick it yourself: 1 for whole numbers in the tens, 0.1 for one decimal place, 10 for numbers in the hundreds.
- If most values crowd onto two or three stems, choose 2 or 5 lines per stem.
- For a back-to-back plot, paste a second data set; it appears on the left.
- Read the plot, the key and the summary, then copy the link to share it.
How to make a stem and leaf plot by hand
John Tukey introduced the stem and leaf display in 1977 as a quick way to write down a set of values, and OpenStax notes it comes from exploratory data analysis. To build one:
- Sort the data from smallest to largest.
- Choose the leaf unit. The leaf is the last digit you keep; everything to its left is the stem.
- List every stem from the smallest to the largest in a column, including stems that have no leaves, so gaps in the data stay visible.
- Write the leaves in increasing order to the right of each stem and add a key.
Worked example: quiz scores
Fourteen quiz scores: 62, 67, 71, 74, 74, 78, 81, 83, 85, 86, 88, 90, 94, 97. With a leaf unit of 1, the tens digit is the stem and the ones digit the leaf:
6 | 2 7 7 | 1 4 4 8 8 | 1 3 5 6 8 9 | 0 4 7
Key: 6 | 2 = 62. Reading the plot: n = 14, the lowest score is 62 and the highest 97, so the range is 35. The median is the average of the 7th and 8th values, (81 + 83) ÷ 2 = 82. Q1 is the median of the lower seven values, 74, and Q3 the median of the upper seven, 88. The repeated leaf on stem 7 makes 74 the mode. The longest row is the 8s, and the scores tail off towards the 60s: a slight left skew.
Split stems
When the data sit on only a few stems the plot is too squashed to show a shape. Values 41, 43, 44, 46, 47, 47, 49, 52, 53, 55, 58, 61 use just three stems; splitting each stem into a low line (leaves 0–4) and a high line (5–9) gives:
4 | 1 3 4 4 | 6 7 7 9 5 | 2 3 5 | 5 8 6 | 1
Each stem now appears twice, and the cluster in the high 40s stands out. Statistics software offers the same option (Stata calls it lines per stem); a five-line split (0–1, 2–3 …) helps with even more crowded data.
Decimals and negative numbers
For decimals choose a leaf unit of 0.1. The data 3.2, 3.5, 3.9, 4.1, 4.4, 4.4, 4.8, 5, 5.6, 6.3 (automatic unit 0.1) become:
3 | 2 5 9 4 | 1 4 4 8 5 | 0 6 6 | 3
with the key 4 | 8 = 4.8. Negative values get negative stems. For -14, -8, -3, 0, 2, 5, 11, 17, 23:
−1 | 4 −0 | 3 8 0 | 0 2 5 1 | 1 7 2 | 3
The −0 stem holds values from −1 to −9, which is why it is needed: −3 and +3 would otherwise share the 0 stem.
Large numbers: truncate or round
For three-digit data such as 127, 134, 138, 142, 149, 151, 156, a leaf unit of 10 keeps the plot to a few stems. Tukey's convention is to truncate (cut off the ones digit), giving:
1 | 2 3 3 4 4 5 5
Rounding instead gives:
1 | 3 3 4 4 5 5 6
The key reads 1 | 2 = 120. Both are acceptable as long as you say which you used. This maker always computes the summary statistics from the exact values, so the median and quartiles are unaffected by the choice.
Back-to-back stem and leaf plot
To compare class A (55, 61, 64, 68, 70, 73, 77, 79, 84, 88) with class B (48, 52, 59, 63, 66, 66, 71, 75, 80, 92), put both on one set of stems. Class B's leaves read outward to the left:
8 | 4 |
9 2 | 5 | 5
6 6 3 | 6 | 1 4 8
5 1 | 7 | 0 3 7 9
0 | 8 | 4 8
2 | 9 | Class A's median is 71.5 and class B's 66. Class B spreads from 48 to 92, a wider range than class A's 55 to 88, which the plot shows at a glance.
Reading shape from a stem plot
- Centre: where the middle leaf falls (the median).
- Spread: the range from the top leaf to the bottom leaf, and how many stems are used.
- Shape: turn the page 90° and the leaf rows look like a histogram. A long tail of short rows at the bottom is right skew; at the top, left skew.
- Gaps and outliers: empty stems between groups of leaves, or a single leaf far from the rest.
Common mistakes
- Leaving out empty stems. Skipping a stem with no leaves hides the gap and distorts the shape.
- Leaves out of order. Unsorted leaves make the median and quartiles hard to count.
- Leaves with two digits. A leaf is always a single digit; choose a bigger leaf unit instead.
- No key. 3 | 2 could mean 32, 3.2 or 320.
- Uneven spacing. When writing by hand, keep leaves the same width so row lengths compare fairly.
Next steps: draw the same data as a box and whisker plot, get the variance and standard deviation with the average and standard deviation calculator, or find where one value ranks with the percentile rank calculator.
Frequently asked questions
What is a stem and leaf plot?
A table that splits each number into a stem (all digits except the last) and a leaf (the last digit). Stems are listed once in a column; the leaves of every value sharing that stem are written in order beside it. OpenStax calls it a stemplot. It shows the shape of the data like a histogram while keeping every individual value.
How do you make a stem and leaf plot?
Sort the data, decide what the leaf unit is (usually ones), write the stems in order from smallest to largest without skipping any, then write each value's last digit beside its stem in increasing order. Add a key such as 7 | 4 = 74 so readers know the place value.
What is the key in a stem and leaf plot?
A one-line example that fixes the place value, for example 3 | 2 = 32 or 3 | 2 = 3.2. Without the key the same plot could describe 32, 3.2 or 320, so every plot needs one.
How do you find the median from a stem and leaf plot?
Count the leaves to get n, then count to the middle position, (n + 1) ÷ 2. Because leaves are in order, you can count straight down the plot. For the 14 quiz scores below the median is the average of the 7th and 8th leaves, 82.
How do you find the mode in a stem and leaf plot?
Look for a leaf repeated on the same stem. In the quiz example, 7 | 4 4 shows that 74 appears twice, so it is the mode.
What are split stems?
Each stem is used on two lines: the first holds leaves 0–4 and the second 5–9. A five-way split uses lines for 0–1, 2–3, 4–5, 6–7 and 8–9. Splitting spreads out data that would otherwise crowd onto a few stems, so the shape is easier to see.
What is a back-to-back stem and leaf plot?
OpenStax calls it a side-by-side stemplot. Two data sets share one column of stems: set A's leaves go to the right and set B's to the left, with B's leaves increasing outward from the stem. It is a quick way to compare two groups such as two classes' scores.
How do you show decimals in a stem and leaf plot?
Use a leaf unit of 0.1 (or 0.01). The stem becomes the whole-number part and the leaf the tenths digit, so 4.8 is written 4 | 8, and the key says 4 | 8 = 4.8.
How do you handle negative numbers?
Give them negative stems. Values from −1 to −9 go on a −0 stem, so −3 is −0 | 3 and −14 is −1 | 4. Negative stems are listed first, most negative at the top, followed by 0, 1, 2 and so on.
Should you round or truncate to make the leaves?
Tukey's convention, repeated in Michael Friendly's York University EDA notes, is to truncate: drop the extra digits, which is faster than rounding, so 127 with a leaf unit of 10 becomes 1 | 2. Rounding (127 → 13 → 1 | 3) is also used. Either is fine if you say which on the key; this maker lets you choose.
When is a stem and leaf plot better than a histogram?
For small data sets, roughly 15 to 150 values, where you want to see the shape and still read off exact values, the median and the mode. For large data sets a histogram or box plot is easier to read.
Sources & method
- OpenStax Introductory Statistics 2e §2.1 — Stem-and-leaf graphs (stemplots), line graphs and bar graphs
- OpenStax Introductory Statistics 2e §2.3 — Measures of the location of the data (quartiles)
- NIST/SEMATECH e-Handbook §7.2.6.2 — Percentiles (quartile interpolation methods)
- Friendly, M. (York University) — Exploratory and graphical methods of data analysis: stem-and-leaf displays (Tukey 1977; truncate rather than round)
- Stata manual — stem: stem-and-leaf displays (truncate/round options, lines per stem)
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