How this instrument works
A stem-and-leaf plot is a simple way to organize a set of numbers so you can see both the distribution's shape and every original data point at once. Each number is split into two parts: the 'stem,' which is all its digits except the last one, and the 'leaf,' which is just that final digit. Numbers sharing the same stem are grouped onto the same row, with their leaves listed in order next to it — so the number 22 becomes stem 2, leaf 2, and sits on the same row as any other number in the 20s.
Turned sideways, the resulting rows of leaves form a shape that looks remarkably like a histogram — longer rows mean more values fall in that range, shorter rows mean fewer — but unlike a histogram, nothing is lost to binning. Every single original value is still sitting right there in the leaves, which makes a stem-and-leaf plot especially useful for small-to-medium datasets where you want to eyeball the distribution's shape (is it symmetric? skewed? does it have gaps or clusters?) without giving up the ability to read off exact values.
This calculator works with non-negative whole numbers, splitting each one by its ones digit as the leaf and everything before it as the stem — the standard convention for this kind of plot, and the version taught in most introductory statistics courses.
- Enter your whole-number dataset into Data set — non-negative whole numbers, separated by commas, spaces or new lines.
- Read Stem-and-leaf plot — each row shows a stem (all digits but the last) followed by a vertical bar, then every leaf (last digit) that shares that stem, listed in ascending order.
- Read the plot sideways to see the distribution's overall shape — longer rows mean more values cluster in that stem's range.
Worked example — the ages 12, 15, 15, 19, 21, 22, 22, 29, 33
Enter 12, 15, 15, 19, 21, 22, 22, 29, 33 into Data set — non-negative whole numbers, separated by commas, spaces or new lines. Splitting each value: 12, 15, 15, and 19 all share the tens digit 1 (stem 1), with leaves 2, 5, 5, 9. The values 21, 22, 22, and 29 share stem 2, with leaves 1, 2, 2, 9. The value 33 stands alone on stem 3, with leaf 3.
Stem-and-leaf plot reads: '1 | 2 5 5 9' on the first row, '2 | 1 2 2 9' on the second, and '3 | 3' on the third. Reading the plot sideways, the shape shows the data is concentrated in the teens and twenties, with a single value trailing off into the thirties — a quick visual read that's still backed by every exact original value, unlike a histogram bar that would hide those individual numbers.
Questions
How is a stem-and-leaf plot different from a histogram?
A histogram groups data into bins and shows only the count in each bin, discarding the individual values once they're binned. A stem-and-leaf plot groups data by shared leading digits (the stem) but keeps every individual value visible as a leaf, so you get the same at-a-glance sense of shape as a histogram while still being able to read off the exact original numbers — useful when you want both the big picture and the precise data at the same time.
What if two numbers have the same stem and leaf?
They both appear — a repeated leaf digit on the same stem row simply means that value occurred more than once in the dataset. For example, the values 15 and 15 both land on stem 1 with leaf 5, so the plot shows '5' twice on that row (as in the worked example above, where stem 1 has leaves 2 5 5 9, reflecting two separate 15s).
Can stem-and-leaf plots handle decimals or negative numbers?
This calculator is built for non-negative whole numbers, splitting on the ones digit as the standard convention. Stem-and-leaf plots can in principle be adapted for decimals (splitting at the decimal point instead) or negatives (with separate negative-stem rows), but those variations use different conventions and aren't what this particular calculator computes.
What's a back-to-back stem-and-leaf plot?
It's a variation that compares two datasets at once by sharing a single column of stems in the middle, with one dataset's leaves extending to the left and the other's extending to the right — useful for visually comparing two related distributions (like before-and-after scores) side by side. This calculator generates a single plot for one dataset rather than the back-to-back comparison version.
Why do the leaves need to be in order on each row?
Sorting the leaves within each stem makes the plot far easier to read at a glance and keeps it consistent with how the technique is conventionally taught and used — an unsorted row of leaves would still contain the same information, but you'd have to scan the whole row to find the smallest or largest value on that stem instead of just reading left to right.