Blog · Finance metrics and formulas · Sales teams
Advertising metrics need consistent definitions before campaigns can be compared. Work through cost, click, purchase and revenue measures from one campaign table, with denominator checks and a clear distinction between revenue return and profit.
Advertising performance metrics measure campaign delivery, audience response, acquisition cost and attributed revenue. A useful metric has a named numerator, denominator and reporting rule. Campaign comparisons become unreliable when the same label means different conversion actions, cost scopes or attribution periods.
An awareness campaign and a purchase campaign serve different jobs. Impressions help describe exposure; they do not establish unique people reached or sales. Clicks describe a response to an ad; they do not prove that the visitor became a customer.
For a commercial review, keep a short chain of measures visible: spending, impressions, clicks, the selected conversion action and the resulting value. A ratio can then be read next to the activity that produced it. A campaign with an attractive acquisition cost but little volume may not support a larger spending decision.
Avoid a universal threshold for a good metric. Compare the same campaign objective, audience scope and conversion definition across comparable periods. A change in measurement rules can produce a larger movement than a change in campaign performance.
The following definitions use media spend and attributed purchases. They form one consistent purchase-campaign dictionary rather than a rule that every advertising platform uses for every campaign type.
| Metric | Formula | What it answers | Definition to preserve |
|---|---|---|---|
| Impressions | Count of recorded ad displays | How much exposure was delivered? | Display-counting rules; impressions are not unique people |
| Click-through rate, CTR | Clicks / Impressions | How often did a display lead to a click? | Which clicks are included |
| Cost per click, CPC | Media spend / Clicks | What did each recorded click cost? | Spend scope and click definition |
| Cost per thousand impressions, CPM | Media spend / Impressions × 1,000 | What did a block of displays cost? | Same delivery and spend population |
| Purchase conversion rate | Attributed purchases / Clicks | How often did a click lead to a counted purchase? | Purchase action, attribution and counting rules |
| Cost per acquisition, CPA | Media spend / Attributed purchases | What was the media cost per counted purchase? | Acquisition means purchase in this report |
| Return on ad spend, ROAS | Attributed net revenue / Media spend | What revenue was attributed per advertising dollar? | Revenue adjustments and attribution basis |
Google Ads defines CTR as clicks divided by impressions. Its broader conversion-rate definition uses eligible ad interactions, which can differ from clicks by ad format. A cross-campaign dictionary must state whether it is using click-based purchase rate or the platform's interaction-based rate.
Similarly, Google's ROAS explanation compares conversion value with advertising cost. If conversion value is a lead score rather than revenue, label the result accordingly. Calling every value-to-cost ratio revenue ROAS hides an important difference.
Covirage is not affiliated with Google Ads.
Consider an illustrative US office products company reviewing a completed September 2026 advertising period. Spend includes media only. Conversion means a completed purchase credited to one channel under a common attribution rule; each purchase appears once across the rows. Attributed revenue is net of discounts and recorded returns for the included purchases.
For this example, all included conversions came from clicks. The counting rules, currency and cutoff are the same for both channels. The raw inputs are:
| Channel | Impressions | Clicks | Media spend (USD) | Attributed purchases | Attributed net revenue (USD) | Variable order costs (USD) |
|---|---|---|---|---|---|---|
| Search | 100,000 | 2,000 | 6,000 | 80 | 24,000 | 14,400 |
| Display | 400,000 | 4,000 | 4,000 | 40 | 12,000 | 7,200 |
| Total | 500,000 | 6,000 | 10,000 | 120 | 36,000 | 21,600 |
The following table shows the calculations. Currency ratios are rounded to two decimal places, rates to one decimal place and ROAS to two decimal places. Totals use the unrounded source values.
| Metric | Search calculation | Search result | Display calculation | Display result | Total calculation | Total result |
|---|---|---|---|---|---|---|
| CTR | 2,000 / 100,000 | 2.0% | 4,000 / 400,000 | 1.0% | 6,000 / 500,000 | 1.2% |
| CPC (USD) | 6,000 / 2,000 | 3.00 | 4,000 / 4,000 | 1.00 | 10,000 / 6,000 | 1.67 |
| CPM (USD) | 6,000 / 100,000 × 1,000 | 60.00 | 4,000 / 400,000 × 1,000 | 10.00 | 10,000 / 500,000 × 1,000 | 20.00 |
| Purchase conversion rate | 80 / 2,000 | 4.0% | 40 / 4,000 | 1.0% | 120 / 6,000 | 2.0% |
| CPA (USD) | 6,000 / 80 | 75.00 | 4,000 / 40 | 100.00 | 10,000 / 120 | 83.33 |
| ROAS | 24,000 / 6,000 | 4.00× | 12,000 / 4,000 | 3.00× | 36,000 / 10,000 | 3.60× |
Search has a higher cost per click and a lower cost per purchase. Its higher purchase rate offsets the more expensive clicks. Display's lower CPC alone would therefore be an incomplete reason to shift spending.
The table describes the observed period. It does not establish that the same ratios will hold after a budget increase, or that every attributed purchase would disappear without advertising.
The count checks come first: 100,000 + 400,000 = 500,000 impressions; 2,000 + 4,000 = 6,000 clicks; and 80 + 40 = 120 purchases. Spend totals $10,000 and attributed revenue totals $36,000.
An identity then checks the purchase funnel:
CPA = CPC / Purchase conversion rate
For Search, 3.00 / 0.04 = $75.00. For Display, 1.00 / 0.01 = $100.00. Calculate the company result from source totals, rather than rounded channel ratios: (10,000 / 6,000) / (120 / 6,000) = $83.33.
Revenue per purchase is 36,000 / 120 = $300. Dividing it by the unrounded total CPA gives 300 / (10,000 / 120) = 3.60×, matching ROAS. The average order value guide explains how returns and order definitions affect that numerator.
These identities detect inconsistent populations. They will fail if CPC uses all clicks while conversion rate uses a different interaction base, or if revenue includes orders omitted from purchase counts. Resolve the mismatch before interpreting the apparent efficiency.
Variable order costs in this example include the product and fulfillment costs associated with the attributed purchases. Advertising is excluded from that column so it can be deducted separately.
| Channel | Contribution before advertising calculation (USD) | Contribution before advertising (USD) | Media spend (USD) | Contribution after advertising (USD) |
|---|---|---|---|---|
| Search | 24,000 − 14,400 | 9,600 | 6,000 | 3,600 |
| Display | 12,000 − 7,200 | 4,800 | 4,000 | 800 |
| Total | 36,000 − 21,600 | 14,400 | 10,000 | 4,400 |
The contribution rate before advertising is 14,400 / 36,000 = 40.0%. Under the same variable-cost relationship, the revenue ROAS needed to cover media spend is 1 / 0.40 = 2.50×. This threshold covers the included variable costs and advertising; it does not cover unallocated fixed costs or establish incremental profitability.
The guide to gross, contribution and net margins explains those different cost boundaries. Keep the cost boundary next to the metric rather than expecting a reader to infer it from the label.
Marketing owns campaign identifiers, spend scope and conversion tracking definitions. Sales confirms whether leads and purchases represent the intended commercial outcome. Finance approves the revenue adjustments and variable-cost scope. The reporting owner checks that the selected rules were applied consistently.
Record the effective date whenever a conversion action, attribution window or cost policy changes. Versioned metric definitions keep a measurement change from being mistaken for a change in advertising performance.
Bring campaign exports and an order file with the conversion definitions, attribution basis and revenue adjustments you use. Covirage maps the columns; its tools compute and check the supplied figures, and the external AI model explains the results with every figure traced to its rows. Create a free Covirage account and bring a sample of your own export.
See metrics governance for the supporting approach to keeping definitions consistent.
Choose measures that match the decision. Exposure metrics help assess delivery, response metrics describe engagement, and acquisition or revenue metrics help assess commercial outcomes. Keep spend and conversion volume beside every efficiency ratio so a small campaign does not look better simply because of limited activity.
CPA divides advertising cost by the chosen acquisition action, which could be a purchase or lead. Customer acquisition cost divides the agreed acquisition costs by new customers. They differ whenever the conversion action, cost scope or distinction between new and existing customers differs.
No. ROAS compares attributed revenue with advertising spend. It leaves out product costs, fulfillment, returns and other expenses unless the numerator is explicitly adjusted. Evaluate contribution after advertising as a separate measure, and distinguish attributed purchases from sales caused by advertising.
It can when the conversion definition allows several actions from the same advertising interaction. A report counting both a form submission and a purchase can record multiple conversions. State the action and counting policy before comparing its rate with a report that counts purchases alone.