Stacked area vs multiple lines
Three series over time can be three lines or three stacked bands. Stacking gives you the total as the top edge but makes every band except the bottom one hard to read individually, because each sits on a moving baseline.
Both charts below are the same data — Revenue by channel — so the difference you see is the chart type, not the numbers.
Multiple lines
Use it when
- Each series has to be readable and comparable on its own.
- The series are not parts of a shared total.
- You need to see one series cross another.
- The values are rates or indices rather than amounts.
Stacked area
Use it when
- The series add up to a meaningful total.
- The composition of that total is the story.
- There are three or four series, not eight.
- Every value is positive.
Which one
Stack only when the sum means something and you want it visible as the top edge. If a reader will need to trace one middle series accurately, unstack it — nobody can read a band that sits on a wobbly baseline.
Questions people ask
- Why is the middle band hard to read when stacked?
- Because its baseline moves with the series beneath it. Readers judge the top edge, not the thickness, so a flat middle band on a rising base looks like it is growing. Put the steadiest series at the bottom to limit the damage.
- What about a 100% stacked chart?
- That trades the total for the mix: every column fills the height and only the shares are visible. It is the right choice when the composition matters and the absolute total does not.