MK-065 | Working backward to target cost per click
For a regular chat, upload packs/mk-065.md. It includes the shared rules, this method, and required references
Purpose
This skill delivers: CPC derived from acceptable CPA and conversion rate
Recalculability does not mean the data is complete; break-even points and cost ceilings apply only under the stated assumptions
Required inputs
Raw inputs: consistent Target CPA, corresponding clicks K, valid orders P from those clicks, click definition, attribution/mature observation window and currency
Method
- Use the specified per-valid-order Target CPA. An approved estimate retains order value times margin times approved ad-allocation fraction, not revenue-target/order-value volume
- Match clicks and their valid orders; purchase conversion rate is P/K. Outbound clicks, all clicks and sessions have distinct denominators. A session conversion rate cannot imply an all-click CPC allowance
- With K positive, matched attribution and a mature window, Target CPC = Target CPA × P/K per corresponding click. For immature or unmatched outcomes, report observed counts and an unset usable rate
- With K zero, conversion is undefined. With K positive and P zero, observed conversion and the formula value are zero but support no positive click allowance; do not recommend a platform zero bid or claim order cost zero
- When matched actual CPC exceeds the candidate allowance, show the gap and conversion rate, then examine creative/audience/landing differences. Recompute after new valid orders, click definitions, windows or Target CPA; CPC alone does not establish the cause
Calculations and interpretation
Hypothetical check: Target CPA 216 with 1,000 corresponding clicks and 10 valid orders gives Target CPC 2.16; 20 verified mature orders changes it to 4.32. If 1,000 denotes sessions, label the result per-session allowance rather than CPC
Decision rules authored by ThinkWithBlack on 2026-10-14; original course sources are retained below
Required output fields
| Order | Field | How to complete |
|---|---|---|
| 1 | Input variable | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 2 | Value | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 3 | Unit and definition | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 4 | Source | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 5 | Formula | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 6 | Result | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
| 7 | Limitations | Use source evidence, an intermediate method result, or an explicit unknown; do not invent information |
Verification cases
MK-065-C05 | A required denominator is zero
Expected: Report that the formula is undefined; do not output a zero cost or an infinite target
MK-065-C06 | Only some costs are supplied
Expected: Retain the partial result and excluded items; do not call it complete profitability
Method sources
Source file: Meta廣告學程 104 廣告的數據決策
Location: CPC
Source basis: extracted from course materials
Source URL: https://docs.google.com/presentation/d/16FiqnSxBs-gSDxsxUBNhWdUX5vZrIWoZPGangj_f_Pk/edit
English translation of source excerpt:
Cost per click (CPC)
