An e-commerce ad getting clicks and impressions does not show by itself that the campaign is successful. What matters is how many of those clicks turn into orders, and how much revenue they bring. To measure this, Google Ads needs to receive purchase conversions with the correct value. When the setup is wrong, the reports, the automatic bidding and your decisions are all based on wrong numbers.

In this guide we explain what a conversion and conversion value are, fixed versus dynamic values, the recommended structure, how to set up a purchase conversion in Google Ads, with Google Tag Manager and from GA4, how to prepare the e-commerce data layer, the importance of the transaction ID and currency, what should count as order value, why Google Ads and GA4 numbers differ and what enhanced conversions are. You can check your return with our ROAS calculator.

What Is a Google Ads Conversion?

A valuable action that a user takes after interacting with your ad, such as a purchase, a form submission, a call or a sign-up. In e-commerce, the main conversion is a successful purchase.

What Is Conversion Value?

What Is Conversion Value?

The value in money that you assign to a conversion, usually the order value. It lets Google Ads optimize for revenue and return, not only for the number of orders.

Fixed vs. Dynamic Conversion Value in E-Commerce

Fixed Conversion Value

The same value for every conversion. It is simple but only suitable when every order is worth about the same.

Dynamic Conversion Value

The real value of each order is sent with the conversion. If your store sells products at different prices, this is the right approach.

How Should the E-Commerce Conversion Funnel Be Structured?

Track the steps of the funnel, but make only the true business outcome the primary conversion.

  • Primary: Purchase, with value, currency and transaction ID.
  • Secondary: Add to cart, begin checkout and other steps, used for observation and learning but not as the main bidding goal in most cases.

Methods for Setting Up an E-Commerce Conversion in Google Ads

Direct Measurement with a Google Ads Tag

The tag fires on the order confirmation event and sends value, currency and transaction ID straight to Google Ads.

Importing the GA4 Purchase Event

If GA4 is linked to your Google Ads account, the purchase event can be imported as a conversion.

Can Both Methods Be Used at the Same Time?

You can, but be careful not to count the same purchase twice. Choose one as primary, or make sure duplicates are avoided with the transaction ID, and keep the other for comparison only.

Creating a Purchase Conversion in Google Ads

  1. Create a new conversion action (website).
  2. Name the conversion clearly, such as “Purchase.”
  3. Set the conversion value: use the dynamic value from your site.
  4. Set the count to “Every.” In e-commerce, each order should be counted separately, so that several orders from the same ad interaction are all measured.
  5. Set it as a primary conversion.
  6. Check the attribution and conversion window to match your sales cycle.

Purchase Conversion Setup with Google Tag Manager

With Google Tag Manager you can manage tags without editing the site code each time.

Data Required for the Setup

Order value, currency, transaction ID and, if you use them, product details and customer type.

How to Prepare the E-Commerce Data Layer

The data layer is a structured object on the page that passes order information to the tag manager.

An Example Purchase Data Layer

window.dataLayer = window.dataLayer || [];
dataLayer.push({ ecommerce: null }); // clear the previous ecommerce object
dataLayer.push({
  event: 'purchase',
  ecommerce: {
    transaction_id: 'T12345',
    value: 249.90,
    currency: 'TRY',
    items: [
      { item_id: 'SKU_001', item_name: 'Product name', price: 249.90, quantity: 1 }
    ]
  }
});

Why Is the Ecommerce Object Cleared?

Clearing the previous ecommerce object before pushing a new one prevents old data from mixing into the new event.

Order Value Must Be Sent as a Number

Send 249.90, not "249,90 TL". Text with currency symbols or commas for decimals can break the value.

Creating Google Tag Manager Variables

  • Conversion value variable: reads ecommerce.value from the data layer.
  • Currency variable: reads ecommerce.currency.
  • Transaction ID variable: reads ecommerce.transaction_id.
  • Customer type variable: (optional) new versus returning, for later analysis.

Creating the Google Ads Conversion Tag

Create a Google Ads conversion tracking tag with your conversion ID and label, and map the value, currency and transaction ID variables.

Custom Event Trigger

Use a custom event trigger set to the purchase event, so the tag fires only after a successful order.

Google Tag and the Conversion Linker

Make sure the Google tag is set up on all pages and the Conversion Linker tag runs on all pages, so that the ad click information is stored and attributed correctly.

Why Should the Transaction ID Be Treated as Mandatory?

It uniquely identifies each order and helps prevent the same order from being counted more than once, for example when the confirmation page is refreshed.

Features of a Correct Transaction ID

Unique per order, the same value in every system (store, GA4, Google Ads), and sent every time.

How Should the Currency Be Sent?

As a three-letter code such as TRY, USD or EUR. Make sure it matches the actual order currency.

What Should Be Included in the Order Value?

Choose a definition and use it consistently in all reports.

Using Product Revenue

The value of the products only, excluding shipping and taxes.

Using Gross Turnover

The full order total, including shipping and taxes.

Using Profit-Based Value

The margin of each order, which lets bidding optimize for profit. It needs reliable cost data.

GA4 E-Commerce Purchase Event Setup

What the GA4 Purchase Event Should Contain

transaction_id, value, currency and items.

Importing the GA4 Purchase Conversion into Google Ads

Link the accounts, mark purchase as a key event in GA4 and import it in Google Ads. For GA4 fundamentals, see Google Analytics.

Why Don’t Google Ads and GA4 Purchase Data Match?

Different attribution models, conversion windows, time zones, data processing times, consent and cookie limits, and the way each system counts repeated orders. Small differences are normal; large ones deserve a check. Compare trends, not just totals.

What Are Enhanced Conversions?

A feature that sends hashed first-party customer data (such as an email address) along with the conversion so that Google can match conversions more accurately when cookies are limited. It must be used with proper consent and privacy compliance.

Testing the Conversion

Place a test order and check: the tag fires only after the successful order, the value, currency and transaction ID are correct, and the conversion appears in Google Ads (it may take some time). Use Tag Manager’s preview mode and the tag diagnostics in Google Ads.

Which Bid Strategy Should Be Used with Conversion Value?

When you have enough conversion data, strategies such as “maximize conversion value” or target ROAS can optimize for revenue. Make sure the value is reliable before relying on them.

Common Mistakes in Conversion Setup

  • Firing the purchase tag on the checkout button click instead of after a successful order
  • Not sending a transaction ID
  • Sending the value as text or with currency symbols
  • Counting the same purchase through both the tag and the GA4 import
  • Using inconsistent value definitions
  • Forgetting the Conversion Linker
  • Not testing with a real order

Conversion Value Setup Checklist

  • Purchase set as the primary conversion, count set to “Every”
  • Dynamic value, currency and transaction ID sent
  • Data layer pushes the numeric value after a successful order
  • Trigger fires only on purchase
  • Conversion Linker active on all pages
  • Duplicate counting avoided
  • Tested with a real order
  • Enhanced conversions considered with consent

For related topics, see Google Merchant Center product upload, Google Ads keyword match options, e-commerce SEO, digital ad management, landing pages and ways to increase e-commerce sales.

Frequently Asked Questions

What is a Google Ads e-commerce conversion?

Measuring a successful purchase on the website by a user who interacted with a Google Ads ad.

On which page should the purchase conversion fire?

The tag should only fire after the payment is successful and the order is created in the system. A click on the payment button should not be treated as a purchase.

What should be sent as the conversion value?

Depending on the business strategy, product revenue, total order amount or profit-based value can be sent. The definition used should be consistent in all reports.

Should a different value be sent for each order?

On e-commerce sites selling products at different prices, the real value of each order should be sent dynamically.

What is a transaction ID?

The order number that uniquely identifies the order. It helps prevent the same order from being counted as more than one conversion.

How is the currency sent?

As a three-letter code such as TRY, USD or EUR.

Should “One” or “Every” be chosen for purchases?

For e-commerce purchases, “Every” should generally be chosen, so that multiple orders from the same ad interaction can be measured separately.

Should add to cart be a primary conversion?

In most e-commerce campaigns, add to cart should be used as a secondary conversion. The main bidding goal should be the real purchase.

Can the GA4 purchase event be imported into Google Ads?

Yes. Once the GA4 and Google Ads accounts are linked, the suitable purchase event can be created as a Google Ads conversion.