A bar chart compares separate categories with gaps between bars, while a histogram shows the distribution of numerical data in continuous bins with no gaps.
Bar chart
- Compares categories (e.g., fruits).
- Bars have gaps.
- Bars can be reordered.
Histogram
- Shows the distribution of continuous data in bins (e.g., test scores).
- Bars touch.
- Bins stay in numeric order.
Key point
Bar chart: categories. Histogram: numeric ranges.
Use
A histogram shows shape: skew, spread and outliers.
Data types
Bar charts display categorical data, such as sales by product or votes by candidate, with separate bars. Histograms show the distribution of continuous numerical data, such as ages, heights or test scores, grouped into ranges called bins.
Gaps between bars
Bars in a bar chart have gaps and can be reordered in any sequence. Histogram bars touch each other, as the data are on a continuous scale, and the order is fixed along the number line.
Axes
In a bar chart, the x axis shows categories, and the y axis shows counts or values. In a histogram, the x axis shows the bins (ranges), and the y axis shows frequency or density.
Bin width
In a histogram, the choice of bin width changes the shape. Too few bins hide detail, and too many create noise. Rules such as Sturges’ rule or the Freedman-Diaconis rule help to choose them.
Shape
Histograms reveal distribution shape such as normal (bell curve), skewed, bimodal or uniform, as well as outliers.
Example
A bar chart might show the number of students by major. A histogram might show how many students scored 60 to 69, 70 to 79, 80 to 89 and 90 to 100 on an exam.
Mistakes
Using a histogram for categories, or starting a bar chart y axis above zero, which exaggerates differences.
Tools
Excel, Google Sheets, Python’s matplotlib and R’s ggplot2 can create both.
Origin
The term histogram was introduced by Karl Pearson in 1891.
Related charts
Pie charts for proportions, line charts for trends and box plots for distributions.
When to use each chart
A bar chart compares separate categories such as product sales by region, with gaps between the bars showing the categories are distinct, and the bars can be reordered. A histogram shows the distribution of a continuous numerical variable such as test scores or ages, by grouping data into bins, and the bars touch because the intervals are continuous and ordered. The statistician Karl Pearson introduced the term histogram in 1891. The height of a histogram bar shows the count or frequency in that bin.
Reading and building a histogram
Bin width changes the shape: too wide hides detail and too narrow looks noisy. A rule of thumb such as Sturges’ rule suggests about 1 plus log base 2 of the number of observations as the number of bins, so 100 data points give about 8 bins. You can read the shape for peaks, skew and outliers. Common mistakes are using a bar chart for continuous data, leaving gaps in a histogram or using uneven bins without adjusting heights. Spreadsheets and tools such as Excel, Google Sheets, Python and R can create both.
Based on data from the American Statistical Association and statistics education references
