Budget Pacing — Why Google Overspends Your Budget and What to Do About It

What Google Does Not Make Obvious

Your daily budget is an average, not a cap. Google can spend up to 2x your daily budget on any given day and up to 30.4x your daily budget in a month. If you set a $100 daily budget, Google can spend $200 on a Tuesday and $50 on a Wednesday, and as long as the monthly total stays under $3,040, they consider that within policy.

This is actually good design for performance—spending more on high-opportunity days and less on low-opportunity days makes mathematical sense. But it creates a real operational problem: clients see a $200 day on a $100 budget and panic. Account managers see unexpected spikes and cannot explain them. And if you change your budget mid-month, the monthly spending limit recalculates, which can cause either overspend or underspend depending on timing.

The Practitioner’s Solution

Deploy budget pacing scripts that track daily spend against your actual monthly target, calculate projected end-of-month spend, and alert when you are off pace. Our open-source budget projection script does exactly this—it writes pacing data to Google Sheets daily so you have a real-time view of where every campaign is tracking.

For clients with strict monthly budgets that cannot exceed a fixed number: use shared budgets across campaigns within the same objective, and set the shared budget to your monthly target divided by the remaining days in the month, adjusted weekly.