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· 3 min read
How to Build a Waterfall Chart That Balances
Manesh Jayawardhana
CIO & Co-founder
Revenue was 120,000 last year and 142,000 this year. The board doesn’t want to know that it went up — they want to know what made it go up, and whether the parts that made it go down are getting worse.
A waterfall chart answers exactly that question, and it has one requirement that a bar chart doesn’t: it has to add up.
How the chart works
Each bar after the first floats. It starts where the previous bar ended and extends by the size of its change, up for positive and down for negative. The final bar returns to the axis to show the closing total.
Read left to right, the position of each bar encodes the running total and its height encodes the step. That dual encoding is why a waterfall communicates a sequence in a way a set of separate bars can’t.
The arithmetic is unforgiving:
closing = opening + sum of all steps
If that doesn’t hold, a category is missing. And here’s why it matters more than in most charts: a waterfall that doesn’t reconcile still looks rigorous. The bars still float, the shape still reads as an explanation, and the missing piece is invisible until someone adds the numbers.
Presenting an unreconciled bridge to people who will add it up is worse than presenting a table.
Getting the steps right
Order them meaningfully. Either chronologically, or grouped so related effects sit together — all the volume effects, then all the price effects. Random order makes the chart harder to read than a list.
Limit to eight or ten steps. Past that the bars get too narrow to label and the eye loses the running position. Group small contributors into “other” and list them beneath.
Separate volume from price. In a revenue bridge these are the two things people actually want distinguished, and merging them into “sales changes” answers nothing.
Label the values. The position encodes the running total, which is hard to read precisely. Numbers on the bars remove the ambiguity.
| Element | Convention |
|---|---|
| Opening and closing | Anchored to the axis |
| Increases | One colour, extending up |
| Decreases | Contrasting colour, extending down |
| Subtotals | Anchored, visually distinct |
Common mistakes to avoid
- Presenting a bridge where the steps don’t sum to the difference — the fastest way to lose a room.
- Using twenty steps because the data has twenty categories.
- Colouring increases and decreases in shades that don’t separate for a colourblind reader; green and red is the common and worst choice.
- Omitting a subtotal in a long bridge, so the reader has to hold the running total in their head.
- Using a waterfall where the question is “how big is each category” rather than “how did we get from A to B” — that’s a bar chart.
How to do it with Waterfall Chart Maker
The Waterfall Chart Maker builds the chart and checks the reconciliation.
- Enter the opening figure, each change in order, and the closing figure.
- Check the closing bar equals opening plus every step — if it doesn’t, a category is missing.
- Group small contributors into “other” rather than shrinking every bar.
- Label the values, since position alone is hard to read precisely.
Other chart builders are in the tools directory.
Frequently asked questions
When is a waterfall the right chart?
When the question is “how did we get from this number to that number”. It’s the standard for profit bridges, revenue variance and budget explanations.
How many steps can it show?
Around eight to ten before the bars get too narrow to label. Group small contributors rather than shrinking everything.
Does it have to reconcile exactly?
Yes. If the steps don’t sum to the difference between opening and closing, something is missing — and presenting it anyway invites exactly the question you can’t answer.
Final thought
Add up the steps before you put the chart in the deck. A bridge that doesn’t balance is a presentation risk dressed as an explanation.