Learn when Google Ads seasonality adjustments help Smart Bidding, when not to use them, and how to calculate and schedule a short conversion-rate change.
For a full campaign walkthrough, watch Darlington's Google Ads Seasonality Adjustments.
A Google Ads seasonality adjustment tells Smart Bidding that you expect a short, unusual change in conversion rate during a future event. It is designed for events such as a brief promotion or sale—not normal busy seasons that Google’s bidding systems can already learn from.
Use one only when you expect a major conversion-rate change, can estimate the size of that change, and the event is short. Google says the tool is best for events lasting 1–7 days and may work less well beyond 14 days.
What a seasonality adjustment changes
A seasonality adjustment changes the conversion-rate assumption used by eligible automated bidding during the scheduled event. It does not directly:
- Increase the campaign budget
- Create more search demand
- Change the website offer
- Fix broken conversion tracking
- Guarantee more conversions
It tells the bidding system that clicks may become conversions at a different rate than usual.
Google currently supports seasonality adjustments for Search, Shopping, and Display campaigns using Target CPA or Target ROAS, plus Performance Max and App campaigns using all bid strategies. They are not supported for Travel campaigns.
Check current eligibility before relying on the tool because platform support can change.
When to use a seasonality adjustment
Use one when all of these conditions are true:
- A future event has a clear start and end.
- The event should materially change conversion rate.
- The change is unusual enough that Smart Bidding may not anticipate it.
- You have evidence from a prior event, test, or business forecast.
- Conversion tracking is reliable.
Examples may include:
- A three-day sale with a proven conversion lift
- A limited booking event that changes customer urgency
- A short promotion with historical results
- An event-specific offer available only for several days
When not to use one
Do not use a seasonality adjustment for:
- Weekends that recur normally
- A busy season that lasts for months
- Weather changes without a reliable conversion-rate estimate
- A budget increase
- A temporary tracking outage
- A new campaign with no useful baseline
- A vague hope that more people will buy
Smart Bidding already responds to many recurring seasonal patterns. Adding an unsupported adjustment can cause the system to bid as if conversion rates will change when they do not.
Seasonality adjustment versus other Google Ads controls
| Situation | Appropriate control |
|---|---|
| Conversion rate will briefly rise or fall | Seasonality adjustment |
| Conversion data will be missing or incorrect | Data exclusion, where eligible |
| The business can spend more profitably | Daily budget review |
| The value of one conversion differs from another | Conversion values or value rules |
| Demand rises but conversion rate stays similar | Budget, targeting, and forecast review—not necessarily a seasonality adjustment |
| The business wants a different balance of cost and volume | Bidding strategy review |
Demand and conversion rate are not the same. More people may search during a seasonal event without the percentage of clicks that convert changing materially.
How to calculate the adjustment
Use the relative change in conversion rate, not the percentage-point difference.
Formula:
(Expected conversion rate − normal conversion rate) ÷ normal conversion rate × 100
Suppose a campaign normally converts 4% of clicks and a three-day promotion is expected to convert 6%.
(6% − 4%) ÷ 4% × 100 = 50%
The correct conversion-rate adjustment is +50%, not +2%.
At 1,000 clicks, that difference would represent:
- Normal result: 1,000 × 4% = 40 conversions
- Expected promotion result: 1,000 × 6% = 60 conversions
- Expected increase: 60 − 40 = 20 conversions
For an expected decline from 5% to 4%:
(4% − 5%) ÷ 5% × 100 = −20%
Do not invent an adjustment simply because the formula is easy. The input should come from credible historical or business evidence.
How to create a seasonality adjustment
Google’s current workflow is:
- Open Tools in Google Ads.
- Open Budgets and bidding.
- Select Adjustments.
- Open the Seasonal section.
- Select the plus button to create an adjustment.
- Choose Conversion rate as the adjustment type.
- Give the event a clear name and description.
- Enter the start and end dates and times.
- Choose the campaign type or specific campaigns.
- Select devices if the event affects them differently and the option is available.
- Enter the expected relative conversion-rate change.
- Review the scope and save the event.
Use the narrowest truthful scope. If only one campaign receives the promotion, do not apply the adjustment to the entire account.
How to plan the event
Confirm the baseline
Measure the normal conversion rate using a period that reflects ordinary performance. Exclude obvious tracking failures or unrelated promotions.
Confirm the conversion action
A conversion-rate increase only means something if the tracked action represents a useful business outcome. Review conversion tracking before changing bids around bad data.
Estimate the change from evidence
Use the same event from a previous year, a comparable promotion, or a controlled business forecast. Consider changes in price, landing page, traffic mix, and offer strength.
Check budget and operations separately
Smart Bidding may bid more aggressively if it expects clicks to convert more often. Confirm that the budget, inventory, call handling, and staffing can support additional demand.
Schedule the exact event window
Do not pad the dates “just in case.” Google says the tool is intended for short events and automatically returns campaigns to normal behavior afterward. No opposite adjustment is required after the event.
What to review afterward
Compare the forecast with the real result:
- Expected versus actual conversion rate
- Spend and clicks
- Qualified calls or leads
- Completed sales or clients
- Cost per qualified lead
- Revenue and margin
- Changes by device or campaign
If the promotion produced more form fills but no more qualified clients, the apparent conversion lift may not represent business improvement.
Record what happened. That creates a better estimate for the next event.
Common mistakes
Using the tool for ordinary seasonality
Smart Bidding already learns recurring patterns. Reserve the adjustment for unusual, short changes.
Entering percentage points instead of relative change
Moving from 4% to 6% is a 50% relative increase, not a 2% adjustment.
Changing too many things at once
If the offer, landing page, budget, targeting, and adjustment all change together, it becomes hard to understand the result.
Applying the wrong scope
An account-wide event can influence campaigns that do not share the promotion. Select only the campaigns, campaign types, dates, and devices affected.
Using an adjustment to hide tracking problems
If conversion data is wrong or missing, repair tracking and review whether a data exclusion is appropriate. A seasonality adjustment describes expected customer behavior; it does not correct bad data.
Frequently asked questions
How long should a Google Ads seasonality adjustment run?
Google says the tool is ideal for short events lasting 1–7 days and may not work as well for periods longer than 14 days.
Do I need a negative adjustment after a promotion ends?
No. Google says campaigns return to their pre-adjustment behavior after the scheduled event.
Does a seasonality adjustment increase my budget?
No. It changes the conversion-rate expectation used by eligible bidding strategies. Budget remains a separate control, though bidding behavior can affect spend within the existing budget.
Can I use a seasonality adjustment for Black Friday?
Possibly, if the event is short and you expect a major conversion-rate change that Smart Bidding may not already anticipate. Use historical evidence and apply the adjustment only to affected campaigns.
What if I expect more searches but the same conversion rate?
A seasonality adjustment may not be necessary. Review budget, demand forecasts, inventory, and staffing instead. The tool is for expected conversion-rate changes, not search-volume changes alone.
Sources
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