---
title: "Which Number Decides Ad Spend: Platform, GA4 or Revenue?"
canonical: "https://www.owox.com/blog/articles/which-number-decides-ad-spend"
updated: "2026-10-26"
---

# Which Number Decides Ad Spend: Platform, GA4 or Revenue?

Platforms, GA4 and revenue rank the same ad spend differently. One year of demo-store data shows how far, and which number decides which budget decision.

[Reporting](/blog/topics/reporting) · Updated October 26, 2026 · 11 min read

![Which Number Decides Ad Spend: Platform, GA4 or Revenue?](https://cdn.owox.com/www/content-marketing-article/which-number-decides-ad-spend/thumbnail/2-ark3em.png/public)

**No single number decides ad spend. Each spend decision has one number that fits it, and the mistake is using the number that happens to be on the screen.** A marketer on r/analytics asked how larger teams decide what becomes the source of truth when millions in paid spend are being allocated across channels. If you own the budget, the answer that survives a meeting is a rule: for this decision, this number, and here is why.

This page shows why the rule is needed with one year of data from a demo online store, ranks five paid platforms by four different numbers, and ends with a table you can paste into a budget document. It does not promise to make the numbers agree: [why they differ](/blog/articles/differences-facebook-ads-google-analytics-4) is a separate question, and a gap you cannot close should be managed, not hidden.

## The short answer

| Decision | The number that decides it | Why | What it cannot tell you |
| --- | --- | --- | --- |
| Which platform gets the next dollar | Store profit per dollar of spend, by the source of the order, over at least two quarters | Platforms count the same customer more than once, and the store counts each order once | Whether the platform caused the order |
| Which creative or audience to keep inside one platform | The platform’s own conversion number | It is the only number that exists at ad level | How the platform compares with another platform |
| Whether total paid spend should go up or down | Total profit against total spend, the blended view | It needs no attribution rule | Where the money should go |
| Whether a platform’s orders would have happened anyway | A holdout test: switch it off in one region and compare | Only a test separates cause from credit | Anything about other platforms |

The rest of the page is the evidence for the first row, the one most budget fights are about.

## Five platforms, one year, four rankings

The data is from our demo project: a synthetic online store whose ad spend, sessions and orders sit in Google BigQuery. The year is 2025. For each paid platform it takes what the platform reports, then what the store recorded: completed orders whose own session came from that platform, and the net profit on them (sale price minus the cost of the products, after cancellations and returns). **The demo store has no GA4 property, so the store’s own records stand in for the number you would otherwise read from GA4 or your order system.**

| Platform | Spend | Platform conversions | Store orders | New-customer orders | Cost per platform conversion | Cost per store order | Cost per new customer | Profit per dollar |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Facebook | $59,852 | 1,214 | 726 | 161 | $49.30 | $82.40 | $371.80 | $3.18 |
| Google | $36,930 | 457 | 309 | 64 | $80.80 | $119.50 | $577.00 | $2.72 |
| TikTok | $36,372 | 763 | 402 | 79 | $47.67 | $90.50 | $460.40 | $2.61 |
| Bing | $33,529 | 488 | 374 | 81 | $68.71 | $89.70 | $413.90 | $3.11 |
| Reddit | $6,439 | 213 | 95 | 27 | $30.23 | $67.80 | $238.50 | $4.82 |

LinkedIn ($18,484) and Twitter ($2,637) are left out of the table. LinkedIn produced 23 store orders and $0.26 of profit per dollar, a poor result on every number, and Twitter reports no conversions at all, so neither helps show why the numbers disagree. That is why the six platforms that report conversions are the ones counted in the 66% below.

![A rank chart of five paid platforms across four numbers: cost per platform conversion, cost per store order, cost per new customer and profit per dollar of spend. TikTok falls from second place on the first number to fifth on the last. Bing rises from fourth to third. Reddit is first on all four.](https://cdn.owox.com/www/content-marketing-article/which-number-decides-ad-spend/body/1-zwnqu6.png/public)

Reddit is first on all four numbers, on the smallest base ($6,439 of spend and 95 orders), so the rank flips below rest on the other platforms. Read the chart for those that move:

*   **TikTok is second on the platform’s own number and last on profit.** It reports 763 conversions against 402 store orders, 90% more, and the budget pays for the difference.
*   **Bing is fourth on the platform’s number and third on the store’s.** It reports 488 conversions against 374 orders, 30% more. The platform with the smaller claim looks worse on its own dashboard and better in the till.
*   **Facebook is third on the first number and second on the other three.** Only the platform’s own count puts it behind TikTok.

A budget set from the first column would have moved money from Bing to TikTok. The last column says that would have been the wrong way round.

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## A number that looks stable can be the one that misleads

TikTok’s cost per platform conversion was close to flat through the year, between $44.50 and $50.50 a quarter. A flat number invites trust. The store’s number did not stay put.

![Two charts for 2025 by quarter. Left: TikTok cost per platform conversion stays between $44.5 and $50.5. Right: net profit per dollar of spend by platform; TikTok falls from $3.75 in the second quarter to $1.92 in the fourth, while Facebook stays near $3 and rises to $3.38.](https://cdn.owox.com/www/content-marketing-article/which-number-decides-ad-spend/body/2-vmaghn.png/public)

TikTok’s profit per dollar went from $3.07 to $3.75, then to $2.18 and $1.92. By the fourth quarter it was the weakest of the four large platforms, and the platform’s own number had not registered anything. Two lessons follow. A platform’s number can stay flat while the business result under it changes. And one quarter is a thin base: among the four large platforms in this data, the best profit per dollar was TikTok in the first quarter, Bing in the second and Facebook in the third and fourth. Decide on at least two quarters, and look at the direction before the rank.

### The gap moved with the result

The same four platforms, with how many more conversions each claimed than the store had completed orders, by quarter of 2025:

| Platform | Q1 | Q2 | Q3 | Q4 |
| --- | --- | --- | --- | --- |
| Facebook | +74% | +69% | +74% | +58% |
| Google | +84% | +47% | +34% | +44% |
| TikTok | +65% | +48% | +121% | +123% |
| Bing | +63% | −9% | +54% | +36% |

TikTok’s claim jumped from about half as many again to more than double the store’s orders in the same two quarters its profit fell. Bing’s best quarter for profit, the second, is the only one where the store recorded more orders than the platform claimed. **The gap and the result moved in the same quarter.** That does not make the gap a forecast, but it is one extra column in the report, and it shows the platform’s flat number was not the whole story.

## A second year: The same method, the other answer

The demo data starts in January 2024, so the same query runs on that year too. The comparison that matters for the rule is between what the platform said and what the store said:

| Platform | 2024: cost per platform conversion | 2024: cost per store order | 2024: profit per dollar | 2025: profit per dollar |
| --- | --- | --- | --- | --- |
| Facebook | $48.74 | $87.00 | $2.78 | $3.18 |
| Google | $80.54 | $119.50 | $2.60 | $2.72 |
| TikTok | $50.76 | $76.80 | $2.91 | $2.61 |
| Bing | $65.54 | $97.70 | $3.02 | $3.11 |

In 2024 the platforms’ own numbers put Facebook ahead of TikTok ($48.74 against $50.76 per conversion), and the store put TikTok ahead of Facebook ($76.80 against $87.00 per order). In 2025 the two disagreed the other way round. By profit per dollar the four ranked Bing, TikTok, Facebook, Google in 2024 and Facebook, Bing, Google, TikTok in 2025. The lesson is not that one platform is better. **It is that the platform’s number cannot tell you which way the disagreement will run next year, and the store’s number can be checked.** The cost-per-new-customer column is shown for 2025 only: with data starting in January 2024, every 2024 customer looks new.

## Why the platform’s number overstates

The mechanics are documented and point the same way: each platform credits itself for conversions inside its own attribution window, so a customer who clicked a Google ad and, a day earlier, saw a Meta ad can be counted by both. [Meta’s Help Center](https://www.facebook.com/business/help/460276478298895) lists the windows, and [why the two sides count differently](/blog/articles/differences-facebook-ads-google-analytics-4) is covered on its own page. In the demo year the six platforms that report conversions claim 3,205 between them against 1,929 completed store orders, 66% more.

GA4 is not a neutral referee either. Its default is [data-driven attribution](https://support.google.com/analytics/answer/12958241), which splits credit across the touchpoints it can see. Non-Google ad traffic [gets a campaign in GA4 only if it is tagged with UTM parameters](https://support.google.com/analytics/answer/11242870). So GA4 is the right place to compare paid with organic and email on one rule. It is the wrong place to tune a single ad, and it will not fix untagged links.

## What the blended number is for

Add up all of 2025: $2,917,862 of net revenue and $1,845,416 of net profit from 5,913 completed orders, against $194,243 of ad spend. Divided out, that is 15.0 of revenue per dollar of spend. This is the number often called MER, marketing efficiency ratio: total revenue divided by total marketing spend.

It is a useful check on the whole, and it answers the question “is the business healthy while we spend this much?”. It cannot answer where to spend, because 71% of the net revenue came from sessions that did not arrive through a paid click. Revenue from sessions that did arrive through paid clicks was $838,912, which is 4.32 per dollar, or $2.72 of profit per dollar. If you set a paid target from the first number you would approve almost any spend.

## When none of these numbers is enough

Every number so far counts orders that had a paid touch. None of them says whether the order would have happened without the ad, and a retargeting campaign aimed at people already in the basket can look excellent on all of them. The only test that answers it is a holdout: switch the platform off in one comparable region or for one audience for a few weeks, and compare the store’s orders with the rest. Run it before a large move, not after.

## How to set it up so the rule holds

1.  **Write down the attribution rule once.** In the demo it is simple: an order belongs to the platform of the session it came from. A simple rule that everyone reads the same beats a clever one that each analyst rebuilds.
2.  **Show two columns for every platform:** what it reports, and what the store recorded, with the gap. A gap that moves between quarters is information.
3.  **Look at two quarters before moving money,** and at the direction, not only the rank.
4.  **Keep the join in one place.** [OWOX Data Marts](https://www.owox.com/app-signup) can hold the SQL for “orders and profit by platform” with an owner and a description, so the report and the meeting read one definition. The wider case for that is in [your numbers, one source of truth](/blog/articles/source-of-truth-your-numbers-answer-to).

## If you have to defend the allocation

The person who builds the report is usually not the person who signs the budget, and the report gets challenged. Three lines hold up when someone asks why money moved:

1.  **Say which decision the number serves, at the top of [the report](/blog/articles/marketing-reports).** “We compared platforms on store profit per dollar over two quarters, because the platforms count the same customer more than once.” That is a method, and a challenge has to attack the method.
2.  **Show the platform’s number next to it, with the gap.** TikTok’s platform number said $47.67 per conversion and the store said $90.50 per order. If you show both, nobody can find the second one later and call it a surprise.
3.  **Say what the number cannot tell you,** and what you will do about it: a holdout test before a large move, and another look at the next quarter. A decision with a stated limit is easier to defend than one that claims certainty.

## The query behind the tables

Hand this to whoever owns your warehouse. It reads the demo store’s views; they swap in your own ad spend, sessions, orders and purchases tables. “New customer” here means the order was the customer’s first completed order in the data, which starts in January 2024.

```
WITH ad AS (
  SELECT source, SUM(spend) AS spend, SUM(platform_conversions) AS platform_conversions
  FROM `owox-demo.ecommerce.ad_performance`
  WHERE date BETWEEN '2025-01-01' AND '2025-12-31' AND medium = 'cpc'
  GROUP BY source
),
first_order AS (
  SELECT customer_id, MIN(order_date) AS first_date
  FROM `owox-demo.ecommerce.orders`
  WHERE status = 'Completed'
  GROUP BY customer_id
),
st AS (
  SELECT s.source,
         COUNT(DISTINCT o.order_id) AS store_orders,
         COUNT(DISTINCT IF(o.order_date = f.first_date, o.order_id, NULL)) AS new_customer_orders,
         SUM(p.line_net_profit) AS net_profit
  FROM `owox-demo.ecommerce.orders` AS o
  JOIN `owox-demo.ecommerce.sessions` AS s ON s.session_id = o.session_id
  JOIN `owox-demo.ecommerce.purchases` AS p ON p.order_id = o.order_id
  JOIN first_order AS f ON f.customer_id = o.customer_id
  WHERE o.order_date BETWEEN '2025-01-01' AND '2025-12-31'
    AND o.status = 'Completed' AND s.medium = 'cpc'
  GROUP BY s.source
)
SELECT source, ROUND(spend) AS spend, ROUND(platform_conversions) AS platform_conversions,
       store_orders, new_customer_orders,
       ROUND(spend / platform_conversions, 2) AS cost_per_platform_conversion,
       ROUND(spend / store_orders, 1) AS cost_per_store_order,
       ROUND(spend / NULLIF(new_customer_orders, 0), 1) AS cost_per_new_customer,
       ROUND(net_profit / spend, 2) AS profit_per_dollar
FROM ad LEFT JOIN st USING (source)
ORDER BY spend DESC
```

For the quarterly or the 2024 view, change the `BETWEEN` dates in both places to the quarter or the year. The totals in the blended section come from the same joins without the `GROUP BY` and with the `medium = 'cpc'` filter moved inside an `IF`. All the figures are synthetic, so no number here describes a real business.

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## FAQ

## Frequently Asked Questions

Which number should I trust to set ad spend?

Trust a different number for each decision. Use the store's profit per dollar of spend to compare platforms, the platform's own conversion number to compare ads inside one platform, and total profit against total spend to set the overall budget. None of them shows whether an ad caused an order; only a holdout test does.

Why do ad platforms report more conversions than my store recorded?

Each platform credits itself for conversions inside its own attribution window, so one order can be claimed by more than one platform while the store counts it once. In the demo store's 2025 data, six platforms claimed 3,205 conversions against 1,929 completed orders, 66% more. The gap moved from month to month, so a fixed correction factor does not work.

Is MER better than ROAS for budget decisions?

They answer different questions. MER, total revenue divided by total marketing spend, shows whether the business as a whole earns enough for what it spends. Platform ROAS ranks ads inside one platform. Neither says which platform should get the next dollar. In the demo store 71% of net revenue came from sessions without a paid click, so MER was 15.0 while revenue from paid sessions was 4.32 per dollar of spend.

How long should I wait before moving budget between platforms?

In the demo store's data one quarter was not enough: the best platform by profit per dollar was TikTok in the first quarter, Bing in the second and Facebook in the third and fourth. Looking at at least two quarters, and at the direction before the rank, is a safer base. That is a reading of one store's data, not a rule for every account.

Can GA4 decide ad spend?

GA4 is useful for comparing paid traffic with organic and email on one attribution rule, and for reading trends. It is a poor place to tune a single ad. Its default model is [data-driven attribution](https://support.google.com/analytics/answer/12958241), and non-Google ad traffic [gets a campaign in GA4 only if it is tagged with UTM parameters](https://support.google.com/analytics/answer/11242870).

## Topics

[Reporting](/blog/topics/reporting)

## Related articles

[Reporting · Marketing Dashboard Examples and Templates, by the Question They Answer · October 30, 2026](/blog/articles/30-best-marketing-dashboard-examples-and-templates)

[Reporting · What is Ad Hoc Reporting? How to Answer a One-Off Question · October 26, 2026](/blog/articles/ad-hoc-reporting)

[Reporting · Advertising Reporting Tools: Which Ones Put Spend Against Store Orders · October 30, 2026](/blog/articles/advertising-reports)

[See all articles →](/blog/articles)

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## Links

Pages this page links to, on this site and on docs.owox.com. Where the page has a Markdown twin, its address follows the link.

- [Reporting](https://www.owox.com/blog/topics/reporting) — /blog/topics/reporting.md
- [why they differ](https://www.owox.com/blog/articles/differences-facebook-ads-google-analytics-4) — /blog/articles/differences-facebook-ads-google-analytics-4.md
- [Book a Demo](https://www.owox.com/book-a-call) — /book-a-call.md
- [OWOX Data Marts](https://www.owox.com/app-signup)
- [your numbers, one source of truth](https://www.owox.com/blog/articles/source-of-truth-your-numbers-answer-to) — /blog/articles/source-of-truth-your-numbers-answer-to.md
- [the report](https://www.owox.com/blog/articles/marketing-reports) — /blog/articles/marketing-reports.md
- [Reporting · Marketing Dashboard Examples and Templates, by the Question They Answer · October 30,…](https://www.owox.com/blog/articles/30-best-marketing-dashboard-examples-and-templates) — /blog/articles/30-best-marketing-dashboard-examples-and-templates.md
- [Reporting · What is Ad Hoc Reporting? How to Answer a One-Off Question · October 26, 2026](https://www.owox.com/blog/articles/ad-hoc-reporting) — /blog/articles/ad-hoc-reporting.md
- [Reporting · Advertising Reporting Tools: Which Ones Put Spend Against Store Orders · October 30,…](https://www.owox.com/blog/articles/advertising-reports) — /blog/articles/advertising-reports.md
- [See all articles →](https://www.owox.com/blog/articles) — /blog/articles.md