Google Ads forecasting means estimating how your campaigns will perform in the future—covering spend, clicks, conversions, CPA, and ROAS—using past account data, upcoming budget and bid changes, plus known seasonal patterns. By 2026, three approaches handle nearly every practical forecasting need: Google Ads Performance Planner for short-term tactical plans, AI-assisted analysis for rapid what-if scenarios, and spreadsheet models for long-range, highly customized projections. Most PPC managers lean on at least two of these. The one many still default to, the Keyword Planner forecast feature, is actually the weakest option, and we’ll break down why. TL;DR: Google Ads forecasting is, at its core, a math exercise. The CPA formula (CPC ÷ conversion rate) and the ROAS formula (conversion value ÷ spend) are identical whether you run them in a spreadsheet, in Performance Planner, or via an AI assistant. Your choice of tool changes speed, usability, and confidence level—not the math itself. Performance Planner is the most precise short-term method for active campaigns because it taps into Google’s auction-level data. The catch: its accuracy is best at monthly or quarterly horizons and falls off for annual projections, and it requires sufficient campaign history to work well. AI-assisted forecasting (Genie) generates scenario-based forecasts in minutes using the methodology described. It excels at spotting momentum changes and inflection points, highlighting nuanced business signals like gradual ROAS erosion or spend instability, and calling out its own assumptions when the baseline forecast appears overly optimistic. Spreadsheet modeling is the winner for long timeframes and bespoke assumptions—anything approaching annual planning, anything that depends on business-specific revenue logic, and anything you need…