What is an attribution window?

The number of days after someone clicks or sees an ad in which the platform still counts their purchase as a conversion from that ad. A 7-day click window counts purchases up to 7 days after a click. Each platform names and sets its windows its own way, and most let you choose.

Is a longer attribution window better?

Neither better nor worse: it answers a different question. A longer window catches buyers who take their time, and it also credits the ad with more sales that other channels helped close. If the extra days add a large share of the count, your buyers take a while to decide. Whether the ad caused those later sales still needs a test.

Which attribution window should I use?

There is no right window for every store. Pick one that fits how long your buyers take, keep it the same when you compare campaigns or months, and remember what it does: it decides what gets counted, not what the ads caused.

Why do my ad platforms report more sales than my store took?

Each platform counts the sales that fall inside its own windows, and one sale can fall inside two platforms' windows at once. Add up what every platform reports and you can end up with more orders than the store took.

Does GA4 use attribution windows too?

Yes. GA4 calls them lookback windows. By default it looks back 30 days for acquisition key events (first visits and first opens) and 90 days for all other key events, and you can shorten both. GA4 and your ad platforms count in different ways, so their numbers will not match exactly.

Attribution Window Calculator

Result

Fill in shorter click window, conversions with the shorter window, longer click window, conversions with the longer window to see the result.

How it works

A click window is how many days after a click a platform still counts a purchase as a conversion from its ad. A longer window counts every conversion a shorter one counts, plus the ones that came later. So the gap between the two counts is exactly the conversions that came in the extra days.

Report the same campaigns, dates and conversion event once with each window, and enter both counts. Only the window may differ, or the gap measures something else.

added conversions =
  longer-window count
  - shorter-window count

share of the longer count =
  added ÷ longer-window count × 100

increase on the shorter count =
  added ÷ shorter-window count × 100

cost per conversion =
  ad spend ÷ conversions,
  for each window

What each term means

Click window: The days after a click in which a platform counts a purchase as a conversion from its ad. See attribution window.
Count: What the platform reports as conversions for your campaigns and dates under one window.
Added conversions: Conversions that came later than the shorter window but inside the longer one.
Cost per conversion: Ad spend divided by the count. The spend stays the same; only the count changes.

What the numbers cannot tell you

A window decides what a platform counts, not what its ads caused. Some of the later conversions would have happened without the ad. How many takes a holdout test or a causal read of your GA4 export. When every platform counts inside its own window, one sale can be counted twice; the ad platform over-reporting checker sets their claims next to what your store took.

What each platform documents

Only what each platform's own documentation says, as read on 26 September 2026. Settings change, so check the page before you rely on a number.

Google Ads: A conversion window is set per conversion action. If you do not change it, a new conversion action counts clicks for 30 days, and you can set anything from 1 to 90 days, depending on the source of conversions. View-through conversions have their own window: 1 day unless you change it.
Meta: Meta's reporting API returns 1-day, 7-day and 28-day click, 1-day view and 1-day engaged view. Since 12 January 2026 it no longer returns 7-day and 28-day view. On 3 March 2026 Meta announced that click-through attribution for website and in-store conversions would count link clicks only, with shares, saves and other non-link clicks moving to engage-through attribution, the new name for engaged-view. Which window lengths an ad set can use depends on its optimisation goal and campaign objective.
TikTok: Windows are set per ad group, when you create it: click-through 1, 7, 14 or 28 days, and view-through off, 1 or 7 days. They cannot be changed once the ad group is published.
GA4: Not an ad platform, but its own attribution has lookback windows: 30 days by default for acquisition key events (first_visit and first_open), which you can set to 7, and 90 days for all other key events, which you can set to 30 or 60.

Google Ads Help, About conversion windows. Read on 26 September 2026.
Meta for Developers, Ads Insights API Metric Availability Updates (16 October 2025). Read on 26 September 2026.
Meta for Business, Simplifying Ad Measurement for a Social-First World (3 March 2026). Read on 26 September 2026.
Meta Marketing API, Ad Set reference, attribution_spec. Read on 26 September 2026.
TikTok Ads Manager Help, How to Create Attribution Windows for your Ad Group. Read on 26 September 2026.
Google Analytics Help, Select attribution settings. Read on 26 September 2026.

Worked example

Example numbers, round on purpose, not a real store:

Shorter click window: 1 day
Conversions with the 1-day window: 400
Longer click window: 7 days
Conversions with the 7-day window: 500
Ad spend on those campaigns: €10,000

1Conversions the longer window adds: 500 - 400 = 100
2Share of the 7-day count: 100 ÷ 500 × 100 = 20.0%
3Increase on the 1-day count: 100 ÷ 400 × 100 = 25.0%
4Cost per conversion, 1-day count: €10,000 ÷ 400 = €25.00
5Cost per conversion, 7-day count: €10,000 ÷ 500 = €20.00

One in five of the conversions this example platform reports on a 7-day window came after the first day. Report the same campaigns on a 1-day window and each conversion looks €5 more expensive. Neither count is wrong; they answer different questions.

Frequently asked questions

What is an attribution window?
The number of days after someone clicks or sees an ad in which the platform still counts their purchase as a conversion from that ad. A 7-day click window counts purchases up to 7 days after a click. Each platform names and sets its windows its own way, and most let you choose.
Is a longer attribution window better?
Neither better nor worse: it answers a different question. A longer window catches buyers who take their time, and it also credits the ad with more sales that other channels helped close. If the extra days add a large share of the count, your buyers take a while to decide. Whether the ad caused those later sales still needs a test.
Which attribution window should I use?
There is no right window for every store. Pick one that fits how long your buyers take, keep it the same when you compare campaigns or months, and remember what it does: it decides what gets counted, not what the ads caused.
Why do my ad platforms report more sales than my store took?
Each platform counts the sales that fall inside its own windows, and one sale can fall inside two platforms' windows at once. Add up what every platform reports and you can end up with more orders than the store took.
Does GA4 use attribution windows too?
Yes. GA4 calls them lookback windows. By default it looks back 30 days for acquisition key events (first visits and first opens) and 90 days for all other key events, and you can shorten both. GA4 and your ad platforms count in different ways, so their numbers will not match exactly.

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