Waterfall chart vs bar chart: when the bridge wins

Both charts use rectangles, and that is where the similarity ends. A bar chart puts every value on the same baseline; a waterfall stacks each one on top of the last, which is why it can show a journey.

Bars answer: which is bigger?

Revenue by region, headcount by team, traffic by channel. The categories have nothing to do with each other except that you want them ranked. A shared baseline is exactly right.

Waterfalls answer: how did we get from A to B?

Opening balance, a series of gains and losses, closing balance. The floating bars carry the reader through the arithmetic, so nobody has to add up eight numbers to check that the ending figure is right.

The give-away test

Ask whether the first and last bars are totals. If they are, a waterfall is the honest chart and a bar chart is hiding the relationship. If nothing sums to anything, a waterfall is theatre.

• Sales by country → bar chart.
• Last year's profit to this year's profit → waterfall.
• Cost by department → bar chart.
• Gross margin to net margin → waterfall.

When both work — as with a P&L that can be ranked or bridged — the waterfall usually wins, because a total the reader can verify buys a lot of trust.