capacity-estimatelisted

> **Reference path.** `<refs>/` below means the shared reasoning layer, which lives at > `skills/stackreason/references/` when installed as a plugin, or at > `~/.claude/skills/stackreason/references/` when the skills are installed individually. > Use whichever exists. # Capacity Estimate Not every question needs a design. Sometimes you want to know whether the answer is $50 or $5,000 before deciding whether the question is worth more thought. This skill does the arithmetic, shows the working, and names the line item that dominates. It takes minutes, not a full interview. ## When to use the design skill instead If the answer would change what they build, they need `stackreason`, not this. Estimates inform decisions; they do not make them. Route to the full design skill when the user is choosing between architectures, when the estimate lands near a budget ceiling, or when they ask "what should I use" rather than "what would this cost". ## Hard Rules 1. **Show every step of the arithmetic.** A number without working cannot be corrected. The user knows their traffic better than you do, and they can only fix your inputs if they can see them. 2. **State units and time bases explicitly.** Per second, per day, per month. Most estimation errors are unit errors, and they are usually off by 86,400. 3. **Give a range, not a point.** Real traffic is not flat. Quote average and peak, and say which drives the sizing. 4. **Name the dominant line item.** Every estimate has one thing t