Module 01 · Marketing Data Science Made Easy

Total ROAS, period-aligned

One ratio. Two inputs. Same calendar window. That is the whole trick.

Definition. Total ROAS = Total Sales ÷ ad spend for a chosen period. It is average portfolio efficiency — not which click “caused” the order.

Total ROAS = Sales (period) ÷ Ad spend (same period)

Decision this module trains Can I defend this week’s Total ROAS to finance with matching dates and one sales basis? If dates disagree, stop — do not brief, do not paste into AI.

Why “period-aligned” is the skill

If sales are MTD and spend is last-30-days, the ratio is fiction. Finance will smell it. So will any AI you paste into. Always write the window on the memo: e.g. 2026-07-01 → 2026-07-31.

Sales — Shopify Total Sales (or Net, if you choose Net and stick to it).
Spend — sum of paid channels for those exact dates (CSV is fine).
Basis — Total vs Net: pick one; never mix mid-week.

Platform ROAS vs Total ROAS

Platform ROAS credits that platform’s model. Total ROAS asks: for every dollar that left the bank for ads, how many dollars of Shopify sales landed in the same window? Both can be useful. Only one is the till desk.

Lab — compute Total ROAS

Sales ($) Ad spend ($)

New vs returning (honest)

You may also track aMER ≈ new-customer sales ÷ spend when you have opaque new/returning counts. Still Level-1: no email CRM required. Do not invent path credit to “explain” new customers.

Retrieve

Without looking: Total ROAS = ? What do you do if sales end-date ≠ spend end-date?

Paid pack has the worksheet: total-roas-retrieval.md (+ worked example).

Open free MER calculator Monday ritual →

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