Bar chart vs line chart
| Bar chart | Line chart | |
|---|---|---|
| Best for | Discrete buckets — comparing each individually | Continuous change — trend over time |
| Number of points | Up to ~30 (depending on layout) | ~10 to thousands |
| Visual emphasis | Each bucket's value | The shape of change |
| Multiple series | Use grouped or stacked bars | Just plot more lines |
| When categories aren't time | Almost always bars | Rarely lines (line implies order) |
The continuity test
Ask: "Do the values between my data points have a meaning?" If you have monthly revenue, the value "between" April and May doesn't mean anything — there is no "April 15.5". Use bars. If you have a stock price sampled every minute, the value between minute 1 and minute 2 does have meaning — there was a real price the whole time. Use a line.
When time-series goes either way
Daily users, weekly signups, monthly revenue — discrete buckets, but many of them. With under about 20 points, bars work and the bucketing is visible. Past 20 points, lines win because the eye can read the trend without counting bars. The cutoff is rough; pick whichever shows your story more clearly.
Combining them
A common business chart is a bar (actuals) plus a line (target or forecast). The bars say "this is what happened"; the line says "this is what we expected." The contrast does the work — anywhere a bar falls short of the line, you have a missed period.
Make this chart on makebarchart.com.
Open the makerWhen neither is right
If you're comparing two variables and want to see correlation, use a scatter plot — neither bars nor lines. If you're showing parts-of-a-whole over time, use a stacked bar or stacked area chart. Bars and lines are not the entire vocabulary of charts.