If you have ever put your GA4 report next to Google Ads and found two different numbers for the same month, you are not alone. It is the most common question I get from new clients, and most of the time the answer is: both are telling the truth, they are just counting different things.
The five reasons the numbers differ
- Attribution. Google Ads credits a conversion to the ad click that led to it. GA4 shares credit across every channel in the journey, so some of that sale may go to email or organic search instead.
- Dates. Google Ads records a conversion against the day of the click. GA4 records it on the day the sale happened. A click on the 30th that converts on the 2nd lands in different months.
- Cross-device journeys. Google Ads can link a click on a phone to a purchase on a laptop for signed-in users. GA4 often sees two separate visitors.
- Consent. When someone declines cookies, Consent Mode v2 lets Google model the missing conversions. Ads and GA4 model in different ways.
- Counting rules. A Google Ads conversion action can be set to count every conversion or one per click. GA4 counts events.
When the gap is a real problem
Some differences are faults, not features. These are worth fixing straight away:
- A platform reports more sales than you made. Usually a purchase tag firing twice, or two tags reporting the same order.
- Conversions suddenly drop after a website change, a new consent banner or a checkout update.
- The gap keeps growing month on month.
How to fix it
Start with your own records: your shop or CRM is the source of truth. Send a unique transaction ID with every purchase so duplicates can be removed. Check that only one tag sends each conversion to Google Ads, either the GA4 import or the Google Ads tag, never both counting as primary. Then add enhanced conversions, and for lead businesses, offline conversions from your CRM, so Google learns from real customers rather than form fills.
Which number should you trust?
For deciding where to spend, trust the number that matches your own sales records most closely over time. For day-to-day bidding, Google Ads needs its own data, so make that data as accurate as you can. If you want a second pair of eyes on your set-up, a tracking check is where I usually start.