How forecasting works - Google Ad Manager Help Skip to main content Google Ad Manager Help Sign in Google Help Help Center Community Google Ad Manager Privacy Policy Terms of Service Submit feedback Send feedback on... This help content & information General Help Center experience Next Help Center Community Announcements Google Ad Manager Forecast your inventory How forecasting works How forecasting works Learn about the parameters used to predict available inventory. #forecasting #checkinventory When you check available inventory, Ad Manager: Analyzes the line item for which you’re running a forecast against competing booked line items.  Looks at unsampled historical traffic from the last 24 months or more as a basis to build and predict future traffic volumes. Analyzes sampled ad characteristics from the more recent past for finer-grained details. Considers seasonal trends in calculations. Using these predictions, Ad Manager runs a simulation for the line item to be forecasted. The output of the simulation shows how many impressions are available for booking and how many matched the targeting of the line item. The projected values are estimates, reference a sample of the overall data, and are not guaranteed. Because our analysis of the recent past is important to get an accurate forecast, we recommend waiting 28 days after adding ad units, ad sizes, key-values, and so forth, before you look at forecasting numbers (though you will see some forecasting numbers sooner). This also applies to new product features. You can also pre-tag your site before launch to see forecasting data as soon as a campaign starts. Lowered line item priority Ad Manager: Looks at the existing state of the network. Runs a simulation for the line item to be forecasted: As part of the simulation, Ad Manager first places the line item at a priority lower than the other line items in the network. This artificially lowered priority means that the forecasted line item isn't able to "steal" impressions from other line items. Next, Ad Manager runs with the forecasted line item at its given priority. Analyzes the simulation results to get the estimated forecasting impressions. Was this helpful? How can we improve it? YesNo Submit Need more help? Try these next steps: Post to the help community Get answers from community members Contact us Tell us more and we’ll help you get there true Forecast your inventory 1 of 6 How forecasting works 2 of 6 Forecasting FAQs 3 of 6 Forecasting and key-values 4 of 6 Pre-tag your site to build forecasts 5 of 6 Determine impressions to book 6 of 6 See the impact of creative restrictions Unlock your revenue with personalized tips today! Visit the Optimization tips for Google Ad Manager page to see personalized suggestions to maximize your revenue. Unlock now ©2026 Google Privacy Policy Terms of Service Language Deutsch‎español‎español (Latinoamérica)‎français‎Indonesia‎italiano‎magyar‎Nederlands‎polski‎português‎português (Brasil)‎Tiếng Việt‎Türkçe‎čeština‎Ελληνικά‎русский‎ไทย‎中文（简体）‎中文（繁體）‎日本語‎한국어‎ English‎ Enable Dark Mode Send feedback on... This help content & information General Help Center experience Search Clear search Close search Google apps Main menu 2631630547366515408 true Search Help Center false true true true true true 148 false false false false false