# Bridge Charts > Waterfall and bridge charts in depth - ARR, revenue, EBITDA, cash, and headcount bridges; anchors, deltas and subtotals; multi-level and stacked bridges; connector lines, sign encoding, label placement, and the footing rule that a bridge which does not sum is a wrong analysis rather than a chart to adjust. Trigger on "waterfall", "bridge", "walk", "how did we get from", "ARR bridge", "cash bridge", "EBITDA bridge", "explain the change", "variance walk", "roll forward chart". - Skill: `lukehle/bridge-charts` (Agent Skill) - Install (CLI): `npx skillmds@latest add lukehle/bridge-charts` - Raw SKILL.md: https://api.skillmd.com/api/skills/lukehle/bridge-charts/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Finance & Business - Author: Lukehle (https://skillmd.com/u/lukehle) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/lukehle/bridge-charts --- # Bridge charts The most valuable chart in finance and the most consistently under-used. A bridge answers *how we got from A to B* — the one question a table of two numbers cannot. Build it with `chartkit.waterfallLayout` (see `svg-charting`), which computes the geometry and, more importantly, checks that the bridge foots. --- ## The rule that comes before any styling > **The bars must sum exactly to the closing anchor.** If they do not, the decomposition is wrong. Fix the analysis. **Never add a plug, never quietly widen "other", never adjust the closing anchor to match.** A bridge that foots because of a plug is a chart that asserts a false explanation. ```js const {bars, domain, footing} = chartkit.waterfallLayout(items); if (footing && !footing.ok) { throw new Error(`Bridge does not foot by ${footing.variance} — fix the analysis`); } ``` Fail loudly. A silent plug is the single worst failure mode in financial charting because it is invisible in the output. --- ## Anatomy | Bar type | Sits | Encodes | |---|---|---| | **Anchor** | On the baseline | An absolute state — opening, closing | | **Delta** | Floating, from the running total | A change | | **Subtotal** | On the baseline | The running total at a stage | ``` ┌───┐ ┌───┐ │ │ ┌──┐ │ │ ┌───┐ │ │ │ │ ┌──┐ │ │ │ │──┘ └──┘ └──┘ └──┐ ┌──┐ │ │ │ │ └───┘ └───────────│ │ │ │ │ │ └───┘ └───┘ Opening New Expan Contr Churn Closing ``` Anchors in a neutral colour. Deltas coloured by direction. The connector lines are not optional — without them the eye cannot follow the cumulative path, and the chart degrades into floating bars. --- ## The four bridges worth knowing ### ARR bridge ``` Opening ARR → New → Expansion → Contraction → Churn → Closing ARR ``` The definitive SaaS growth visual. Rules: a customer appears in exactly one bucket per period; downgrade-to-zero is churn, not contraction; group New and Expansion visually to make gross-add versus gross-loss readable at a glance. ### EBITDA / margin bridge ``` Prior EBITDA → Volume → Price → Mix → COGS → Personnel → Other opex → Current EBITDA ``` Order matters here: put the **operational drivers first and the one-offs last**, so the reader sees the underlying movement before the noise. Add a note reconciling to a clean run rate — that is what gets used for forecasting. ### Cash bridge ``` Opening cash → Collections → Payroll → Vendors → Capex → Financing → Closing cash ``` **Outflows always negative.** A cash chart with positive outflows will be misread by someone in a board meeting. Consider a subtotal after operating items to separate operating from financing. ### Budget-to-actual bridge ``` Budget → Volume variance → Price variance → Mix → Timing → Actual ``` Reconciles the gap in driver terms rather than line-item terms. Far more useful than a variance table when someone asks "why did we miss". --- ## Multi-level and stacked bridges **Stacked deltas** — when a single bar decomposes further (Expansion = upsell + cross-sell + price): stack within the bar, keep the stack order consistent across bars, and only do this when the sub-components are genuinely comparable. Beyond two or three sub-parts it becomes unreadable. **Subtotal bridges** — for long walks, insert subtotals to create readable stages: ``` Opening → [operating deltas] → Subtotal: operating → [financing deltas] → Closing ``` **Nested bridges** — a summary bridge with a second bridge decomposing one bar. Excellent for drill-down (`app-interaction-patterns`); the child bridge must foot to the parent bar exactly, and it should say so. --- ## Encoding **Sign.** Two colours plus position. Increases and decreases must differ in **lightness** as well as hue, or the chart dies in greyscale. Never red/green alone. **Direction is not goodness.** A rise in churn is an increase *and* bad. Decide whether the chart encodes direction or goodness, then say which in the legend. Encoding both in one colour scale guarantees a misread. **Anchors are neutral** — grey or a muted tone. They are states, not changes, and colouring them like deltas implies movement. **Order** is chronological or logical, never sorted by size. A bridge sorted by magnitude is no longer a walk. --- ## Labels Every bar carries its value. A bridge the reader has to estimate from axis position has failed. - **Value inside the bar** when it fits, **above/below** when it does not - **Signed deltas** (`+180K`, `−38K`) — the sign is information - **Anchors labelled with the absolute**, deltas with the change; never mix the two conventions - Use `chartkit.avoidOverlap` for dense bridges — it preserves order while separating labels - Add the **percentage of the opening** for context where it helps: `+180K (+3.9%)` Category labels below the axis, rotated only as a last resort — rotated labels are a sign the chart is too narrow or has too many bars. --- ## How many bars Five to nine is the sweet spot. Beyond about twelve it stops being readable. Too many? Group the small ones into "Other" — but **"Other" must be smaller than the smallest named bar.** If it is not, you have hidden the story in a residual, which is a named anti-pattern. Break out the next largest until that holds. --- ## Scale - **Zero baseline**, unless every bar sits far from zero and the deltas would be invisible — in which case truncate deliberately, mark the axis break, and say so. - Domain must include zero when any bar crosses it. - For a bridge where deltas are tiny relative to the anchors, consider charting only the deltas with the anchors as text. The alternative is five bars of identical apparent height. --- ## Checklist - [ ] `footing.ok` is true — checked in code, not by eye - [ ] Connector lines present - [ ] Every bar labelled with a signed value - [ ] Anchors visually distinct from deltas - [ ] Sign survives greyscale - [ ] "Other" smaller than the smallest named bar - [ ] Order is chronological or logical - [ ] Title states the finding, not "ARR Bridge" (`chart-annotation`) - [ ] As-of and period status present --- ## Related skills - `svg-charting` — `waterfallLayout` and the footing check - `chart-selection` — when a bridge is the right form - `chart-annotation` — the takeaway title - `variance-charts` — the budget-to-actual sibling - `financial-tables` — the table that accompanies a bridge