Histogram maker
A histogram groups numbers into bins and stacks them. The number of bins changes the story, so try a few and see.
Bins are rounded to a tidy width of 10, starting at 50. Labels show each bin's left edge; a value on an edge goes in the bin to its right.
| Bin | Count | Share |
|---|---|---|
| 50 to <60 | 1 | 5.0% |
| 60 to <70 | 5 | 25.0% |
| 70 to <80 | 8 | 40.0% |
| 80 to <90 | 4 | 20.0% |
| 90 to <100 | 2 | 10.0% |
Bins change the story
Drag the bins slider all the way down and the histogram becomes one uninformative block. Drag it all the way up and it turns into a spiky comb where every value has its own bar. Somewhere in between, the real shape appears. Statisticians have formulas for a sensible default (Sturges' rule is used here; Freedman–Diaconis is common for large or skewed data), but the honest test is whether the overall shape holds across a few nearby choices.
How to describe what you see
- Shape: symmetric, skewed right (long tail to the right, like incomes), skewed left, unimodal or bimodal.
- Centre: roughly where half the area is on each side (the median).
- Spread: how wide the bulk of the bars is.
- Unusual values: gaps and isolated bars far from the rest.
Tick the normal overlay to compare your data with a bell curve of the same mean and standard deviation. For the counts behind each bar, including relative and cumulative frequency, use the frequency distribution table.
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Questions students ask
How many bins should a histogram have?
A common starting point is Sturges' rule, k = 1 + log₂(n), which is what this tool uses by default. Try fewer bins for small data sets and more for large ones, and check that the overall shape stays the same.
What is the difference between a histogram and a bar chart?
A histogram shows a numeric variable split into touching intervals; the bars touch because the scale is continuous. A bar chart compares separate categories, so its bars have gaps.
Which bin does a value on the boundary go into?
Here, each bin includes its left edge and excludes its right edge, except the last bin, which includes both. So with bins 10–20 and 20–30, the value 20 counts in 20–30.
How do I describe the shape of a histogram?
Look at centre, spread, shape and unusual values. Shape words include symmetric, skewed right (long tail to the right), skewed left, unimodal and bimodal.