How to make a stem-and-leaf plot
- Enter 1–200 finite numbers separated by commas, spaces, semicolons, or line breaks.
- Choose leaf unit 1 for whole numbers, 0.1 for tenths, or 0.01 for hundredths.
- Select Calculate. The tool sorts observations, creates stems, and sorts leaves within each row.
- Read the key before interpreting a row, especially when the data includes negative values.
- Copy the plain-text plot if you need it in notes.
How stems, leaves, and the key work
Each leaf represents exactly one observation, so repeated values produce repeated leaves. The reconstruction rule is (stem × 10 + leaf) × leaf unit. With unit 1, 3 | 2 means 32. With unit 0.1, 3 | 2 means 3.2. With unit 0.01, 3 | 2 means 0.32.
The key is generated from an actual entry in the plot. This prevents the chosen precision from being ambiguous. The plot is alphanumeric rather than a decorative chart, allowing exact observations and the distribution shape to be read together. Reading leaves from left to right within a row follows ascending numeric order, while moving down through the stems continues that same ordering.
Negative values and zero
The tool uses floor-based stems so leaves always stay between 0 and 9 and every row remains numerically sorted. For example, with leaf unit 0.1, −1 | 9 reconstructs (−1 × 10 + 9) × 0.1 = −0.1. A value of −1.2 is −2 | 8.
This notation can look different from classroom conventions that write a minus sign before a positive stem and reverse negative leaves. Always use the displayed key and formula. Negative stems appear before stem 0; zero and small positive values then follow in order.
Worked examples
For 12, 14, 14, 19, 21 with leaf unit 1, the rows are 1 | 2 4 4 9 and 2 | 1. The duplicate 14 remains visible as two leaves.
For −1.2, −0.1, 0, 0.2, 0.2, 1.1 with leaf unit 0.1, the stems are −2, −1, 0, and 1. Reconstructing every leaf produces the original sorted list, including both copies of 0.2.
Precision and output limits
Choose the smallest supported leaf unit that exactly matches the recorded measurements. Whole-number counts normally use 1; measurements recorded to one decimal place use 0.1; measurements recorded to two decimal places use 0.01. A finer unit creates more possible stems and can make a wide-range dataset harder to read. A coarser unit is not a rounding option here: if it would discard recorded digits, validation stops and asks for a matching unit.
- Input values must match the leaf unit exactly. At unit 0.1, 1.2 is valid but 1.23 is rejected; the tool never silently rounds it.
- The list is limited to 200 observations and the plot to 100 stem rows. Choose a coarser supported unit or a smaller range if the row limit is exceeded.
- Very large values that cannot be converted to safe integer leaf positions are rejected rather than approximated.
- A long row scrolls inside its own output area on a narrow screen. It does not widen the whole page.
Frequently asked questions
Does sorting remove duplicates? No. Every leaf is one observation. Why does a negative value use an unexpected stem? The floor-based rule keeps leaves 0–9 and preserves numerical order; use the formula in the key. Can the tool guess precision? No, because an explicit unit makes the original-value relationship clear. Does it make split stems or back-to-back plots? No. Those are outside this focused single-dataset tool. When is a stemplot useful? It is most readable for small or moderate datasets where retaining individual values matters.