Statistics Calculator
Stem and Leaf Plot Calculator
Instantly generate an accurate stem-and-leaf plot (stemplot) from any numerical dataset. Simply enter your data as comma or newline-separated numbers, choose your stem unit, and the calculator constructs a properly aligned plot — complete with the sorted dataset, key, range, and a step-by-step construction breakdown.
Stem and Leaf Plot
Visualize data distribution with a stem-and-leaf display
Results
Enter a dataset to generate the stem and leaf plot
What is a Stem and Leaf Plot?
A stem-and-leaf plot is an exploratory data analysis tool that displays quantitative data in a graphical format while retaining the exact numerical values. Each data point is split into two parts:
- Stem — all digits except the last one (or the leading digits, depending on the stem unit)
- Leaf — the last (rightmost) digit after splitting at the chosen unit
The stems are listed in ascending order in a column. For each stem, its corresponding leaves are written in a row to the right of a vertical divider ("|"). Reading across a row reconstructs the original data values. The resulting shape instantly reveals whether data is symmetric, right-skewed, left-skewed, or bimodal.
Stem-and-leaf plots were introduced by statistician John Tukey in 1977 as part of his influential Exploratory Data Analysis (EDA) framework and remain one of the most effective tools for visualising small datasets in statistics education.
How to Construct a Stem and Leaf Plot
- Sort the data in ascending order.
- Choose your stem unit — Ones for data up to 99, Tens for data up to 999, Hundreds for larger values.
- Split each value into a stem and a leaf. For ones unit: 47 → stem = 4, leaf = 7.
- List all unique stems in a column (include empty stems between min and max for clarity).
- Record the leaves for each stem in order, separated by spaces.
- Add a key (e.g., "2 | 3 = 23") so the reader knows how to interpret the plot.
Split Formula
Stem = floor(value ÷ stem_divisor)
Leaf = value mod stem_divisor ÷ (stem_divisor ÷ 10)
For ones unit (÷10): value 47 → stem = floor(47/10) = 4, leaf = 47 mod 10 = 7
For tens unit (÷100): value 145 → stem = floor(145/100) = 1... wait, 14 → stem 14, leaf 5
Example Stem and Leaf Plots
Example 1 — Basic Monohybrid Data (Ones Unit)
Data: 23, 25, 31, 34, 38, 42, 45, 47, 51, 55
2 | 3 5
3 | 1 4 8
4 | 2 5 7
5 | 1 5
Key: 2 | 3 = 23
- Range: 23–55
- n = 10 values
- Distribution appears roughly uniform across stems
Example 2 — Larger Numbers (Tens Unit)
Data: 145, 152, 158, 163, 170, 175, 183 — Stem Unit: Tens
14 | 5
15 | 2 8
16 | 3
17 | 0 5
18 | 3
Key: 14 | 5 = 145
- Range: 145–183
- n = 7 values
- Stems represent the "tens" place (14 = 140s, 15 = 150s, ...)
Example 3 — Identifying Skew
Data: 10, 12, 14, 14, 15, 21, 22, 32, 45, 58
1 | 0 2 4 4 5
2 | 1 2
3 | 2
4 | 5
5 | 8
Key: 1 | 0 = 10
- Most values cluster in the 10s — right-skewed distribution
- Skew is immediately visible from the plot shape
When to Use a Stem and Leaf Plot
- Small datasets (n ≤ 100): Stemplots work best with 10–50 data points. With too few points the shape is unclear; with too many, the leaves become unmanageable. For larger datasets, use a frequency histogram instead.
- Preserving original values: Unlike histograms which group data into bins, stem-and-leaf plots preserve every data point. This is important when you need to recover exact values after visualising the distribution.
- Quick distribution check: The visual shape of the plot immediately shows whether the data is symmetric (bell-curve shape), right-skewed (tail extends right), or left-skewed — without any additional calculations.
- Identifying modes and clusters: Rows with many leaves indicate where values are concentrated. Gaps (rows with no leaves) show where the distribution has breaks. Outliers appear as isolated leaves far from the main cluster.
- Classroom and EDA use: Stem-and-leaf plots are a staple of introductory statistics, standardised tests (AP Statistics, GCSE), and exploratory data analysis. They combine the functions of sorting, tabulating, and graphing into one step.
Choosing the Right Stem Unit
The ideal stem-and-leaf plot has between 5 and 20 stem rows. If your plot has too few rows (everything on 1–2 stems), switch to a smaller stem unit. If you have too many rows spread thin (every stem has only 1 leaf), switch to a larger stem unit. Aim for a display that reveals the overall shape clearly without being too compressed or too sparse.
Frequently Asked Questions
- What is a stem and leaf plot?
- A stem-and-leaf plot (also called a stemplot) is a statistical display that organises numerical data while preserving the original values. Each data value is split into a "stem" (all digits except the last) and a "leaf" (the last digit). The stems form a column on the left and the leaves fan out to the right, creating a visual shape similar to a histogram that also shows every individual data point.
- How do you read a stem and leaf plot?
- Read each row by combining the stem (left of the "|" divider) with each leaf (right of the divider). For example, in a ones-unit plot, a row reading "3 | 1 4 8" represents the values 31, 34, and 38. The key (legend) shown below the plot gives you a concrete example: "2 | 3 = 23".
- When should I use tens or hundreds as the stem unit?
- The stem unit determines the granularity of your plot. Use "ones" (default) for data roughly in the range 0–99. Use "tens" for data in the range 100–999 (e.g., test scores of 140–190 would have stems 14, 15, 16 ... and leaves of the units digit). Use "hundreds" for data in the thousands range. The goal is to produce a plot with 5–20 stem rows for a readable display.
- What are the advantages of a stem and leaf plot over a histogram?
- Unlike a histogram, a stem-and-leaf plot preserves every original data value, making it possible to reconstruct the full dataset from the plot alone. It also reveals the shape of the distribution (symmetric, skewed, bimodal) and lets you quickly identify the mode, median, and range without additional calculations. They are ideal for small-to-medium datasets (typically up to 50–100 values).
- What is a back-to-back stem and leaf plot?
- A back-to-back (or two-sided) stem-and-leaf plot places two datasets on opposite sides of a common stem column, allowing direct side-by-side comparison of two groups. For example, comparing test scores of Group A and Group B. This calculator generates a standard one-sided plot; back-to-back plots are useful for comparative analysis.
- Can a stem and leaf plot handle decimals?
- Standard stem-and-leaf plots are designed for whole numbers. When decimal data is entered, this calculator rounds each value to the nearest integer before plotting. For decimal-heavy datasets, consider using the ones stem unit with values multiplied by 10 (e.g., treat 2.3, 2.5, 3.1 as 23, 25, 31), then note in your key that "2 | 3 = 2.3".