Reconcile served and billed spend before arguing over ROAS
A reporting-cost total and an invoice-cost total can differ after adjustments. A reproducible illustrative example with editable inputs and explicit limits.
A reporting-cost total and an invoice-cost total can differ after adjustments. This lab compares ROAS using each denominator while keeping revenue constant. The gap is a cost-definition difference, not evidence that the campaign acquired more valuable players.
Define the calculation before using it
Enter the served cost and actual billed cost for the same scope, then apply the same revenue numerator to both. Preserve adjustment categories outside the aggregate calculator so the difference can be traced. Do not assume every discount, credit or tax belongs in both operational reporting and financial measurement in the same way.
Work through the synthetic example
At 5,000 revenue, 10,000 served cost and 9,500 billed cost, the two ratios are 50% and approximately 52.63%. The 500-unit cost difference explains the change. A review should state which ratio it uses and why, rather than switching denominators when one produces a more favourable story.
| Output | Worked-example result |
|---|---|
| Served-cost ROAS % | 50.0000 |
| Billed-cost ROAS % | 52.6316 |
| Cost difference | 500.0000 |
Use the artifact and preserve its assumptions
Open the editable calculator to change the inputs and inspect the sensitivity view. The CSV records synthetic inputs and expected outputs; the JSON fixture keeps the equations available for reproduction. These calculations have been checked against the stated example. No measured campaign data is included.
The sensitivity rows vary only billed by 20% below and above the entered value. They are scenarios, not confidence limits or a forecast distribution. A row outside the model’s constraints is labelled rather than turned into a plausible-looking result. Save the chosen inputs with the decision so another reader can distinguish a changed assumption from a changed formula.
Evidence and limits
Google distinguishes served cost from billed cost after adjustments. Choose and document the cost basis used in this worksheet; its production, contribution and cash assumptions are our teaching examples, not provider benchmarks. See Manage your spend in Google Ads, especially “Access your billing and cost data; View costs from reports”.
This example does not estimate credits or assert that a particular account received them. Reconcile the provider’s actual billed-cost record and finance treatment before using the number in a budget decision.
Background: UA metrics explained: CPI, ROAS, LTV and payback and Reading an MMP dashboard without fooling yourself. These existing articles provide context; the present calculation does not verify every archived claim.
