# Estimation > Estimation - Skill: `meaningfy-ws/estimation` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds@latest add meaningfy-ws/estimation` - Raw SKILL.md: https://api.skillmd.com/api/skills/meaningfy-ws/estimation/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: meaningfy-ws (https://skillmd.com/u/meaningfy-ws) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/meaningfy-ws/estimation --- # Estimation > **Provisional pending the first-engagement gate.** This wiring is the floor, not the finished standard; > refine it after the first real paid engagement is estimated and delivered against. ## Overview A **fixed-cost scoping / estimation discipline** that de-risks fixed-cost bids. It is deliberately **light — a checklist plus a method, not a model**. The job is to turn an engagement into a defensible number: a **work breakdown**, **PERT-weighted effort** with **uncertainty ranges**, explicit **assumptions & exclusions**, and **contingency** — then hand those to the SoW so the price and the scope boundary rest on the same evidence. It is independently triggerable (any "estimate this" / "PERT estimate" request) and is also the **pricing step** of the [`proposal-writing`](../proposal-writing/SKILL.md) flow. It composes by reference: the estimate decomposes against the build breakdown owned by [`epic-planning`](../epic-planning/SKILL.md), and its sequencing/roadmap framing comes from [`decision-package`](../decision-package/SKILL.md). It restates neither. ## What it covers (R4) 1. **Decomposition (work breakdown).** Break the engagement into estimable leaf items — small enough that each can carry a three-point estimate. For build-tier work, decompose against the EPIC/PLAN breakdown from [`epic-planning`](../epic-planning/SKILL.md); do not invent a parallel breakdown. 2. **Uncertainty ranges.** Each leaf gets a range, not a point. PERT (below) is how the range becomes a weighted estimate plus a variance you can roll up. 3. **Assumptions & exclusions.** State what the number assumes (inputs, access, decisions, availability) and what it explicitly excludes. **The exclusions are the SoW out-of-scope list** — one list, two documents (see [`proposal-writing`](../proposal-writing/SKILL.md)). 4. **Contingency.** A buffer sized from the rolled-up variance and the assumption risk — not a flat guess. The [worksheet](references/pert-worksheet.md) shows the roll-up. 5. **Link to the SoW scope boundary.** The breakdown's leaves are the in-scope items; the exclusions are the out-of-scope items; the PERT total + contingency is the fixed-frame price. ## Techniques: PERT is the default Multiple estimation techniques exist; **PERT is the favoured system** here because three-point estimates make fixed-cost uncertainty explicit and roll up into a defensible contingency. **PERT (three-point) — the default.** For each leaf, capture three estimates and weight them: ``` Expected (TE) = (O + 4·M + P) / 6 SD = (P − O) / 6 Variance = SD² ``` - **O** = optimistic (everything goes right), **M** = most-likely, **P** = pessimistic (plausible worst case — not catastrophe). - Roll up: **engagement TE = Σ leaf TE**; **engagement SD = √(Σ leaf variances)**. - Size **contingency** from the rolled-up SD (e.g. a one- or two-SD buffer for the confidence level the fixed frame needs). The [worksheet](references/pert-worksheet.md) does the arithmetic. **Alternatives (use when they fit better, or to triangulate):** | Technique | Use when | |-----------|----------| | **Analogous** (top-down, from a similar past engagement) | Early, little detail; a quick sanity anchor | | **Parametric** (units × rate, e.g. per source system / per ontology module) | The work scales with a countable driver | | **Bottom-up** (sum of leaf estimates) | Detail exists; pairs naturally with PERT per leaf | Triangulate when the stakes are high: a PERT bottom-up that disagrees with an analogous top-down is a signal to re-examine the breakdown. ## Gantt / scheduling is EXTERNAL This skill produces the **work breakdown + estimates**. It does **not** draw Gantt charts or schedules. Scheduling (dependencies, calendar, resource levelling, the Gantt itself) is rendered in **external tools — Smartsheet or MS Project** — by importing the work breakdown. Do not attempt to draw Gantts in-repo; produce a clean breakdown that those tools can consume. Sequencing *intent* (pilot → scale order) comes from [`decision-package`](../decision-package/SKILL.md); the calendar rendering of it is the external tool's job. ## The checklist Run before any number leaves the room: - [ ] Work broken into leaves small enough for a three-point estimate (decomposed against the `epic-planning` breakdown where build work is involved). - [ ] Each leaf has O / M / P and a PERT expected value. - [ ] Variances rolled up; engagement SD computed. - [ ] Contingency sized from the rolled-up SD + assumption risk (not a flat percentage guess). - [ ] Assumptions listed; each risky assumption has an exclusion or a stop/extend trigger. - [ ] **Exclusions = the SoW out-of-scope list** (the invariant in `proposal-writing`). - [ ] Triangulated against at least one alternative technique when the bid is large. - [ ] Work breakdown exported clean enough for Smartsheet / MS Project to schedule. The fillable worksheet (PERT table + roll-up + contingency) is in [`references/pert-worksheet.md`](references/pert-worksheet.md); the full checklist is in [`references/estimation-checklist.md`](references/estimation-checklist.md). ## Boundary & Related Skills **This skill OWNS:** the **estimation / scoping discipline** — PERT + work breakdown + uncertainty ranges + assumptions/exclusions + contingency, and the clean breakdown that external scheduling tools consume. **This skill DELEGATES:** - The proposal / SoW wrapper (and the scope-boundary discipline the exclusions feed) → [`proposal-writing`](../proposal-writing/SKILL.md). - The build breakdown the estimate decomposes against → [`epic-planning`](../epic-planning/SKILL.md). - Sequencing / roadmap intent (pilot → scale) → [`decision-package`](../decision-package/SKILL.md). - The calendar/Gantt rendering → **external tools** (Smartsheet, MS Project) — out of repo. **Related:** `proposal-writing`, `epic-planning`, `decision-package`. ## Tone & style British English. Terse and numeric. Every number traces to a leaf, an assumption, and a technique; no unexplained round figures. A point estimate without a range is a smell — show the range and the contingency that covers it.