Let’s be real: When it comes to Google Ads, heart-racing, adrenaline-pumping, edge-of-your-seat excitement is what you might call ‘rare’.

And few topics represent the exact opposite of that quite as much as Google Ads forecasting. 

If we’re being honest, it’s a complete snoozefest. And because of that, most marketers either A) don’t take forecasting seriously, using outdated practices or relying on Google’s own (slightly questionable) forecasting tools, or B) neglect it completely.

Little do they know, when you master forecasting, it’s like having a PPC cheat code. A crystal ball with which to gaze upon the future of your ad performance - or, an invaluable tool when it comes to appeasing clients or stakeholders and justifying higher budgets.

To help marketers fully understand and wield the potential of proper forecasting, we had to get advice from one of the best in the business. And after talking to Ed Leake, we got it.

Ed is a renowned paid media expert with over £500 million in managed ad spend, decades of experience, and is the founder of God Tier Ads - where he helps thousands of PPC managers stay on top of their game. 

Watch our full discussion with Ed here, where he brings battle-tested wisdom to a discipline too often misused or misunderstood. 

Or, keep reading to get the key takeaways on building better forecasting, managing seasonality, and more. You’ll also get the link to Ed’s free forecasting spreadsheet.

Timestamps:

0:00 - Intro
02:12 - Ed’s approach to copywriting
04:02 - The problems with Google’s forecasting tools
08:39 - Accounting for seasonality in forecasting
14:32 - Why impression share is important
17:55 - Accounting for Remarketing
21:00 - Should you exclude brand from PMax?
22:45 - PMax or Standard Shopping?
24:41 - Will AI invalidate forecasting?
27:34 - Putting the work in
29:32 - Final thoughts 

Why forecasting (still) matters

In a world increasingly dominated by Google’s automation and black-box performance tools, it’s easy to assume forecasting is becoming obsolete. But Ed disagrees:

“We are going to get into a weird world if we don’t need to forecast. Because if all we do is add budget and trajectory into the platform… how does that work?”

Google Ads may be headed towards a keywordless future, but marketers still need clarity. Forecasting offers a rare moment of proactive control - a chance to align ad performance with real business outcomes before spend ever hits the account.

Forecasting isn’t just about numbers. It’s about thinking. According to Ed, forecasting is one of the few remaining disciplines that forces marketers to step out of the interface and consider the bigger picture:

• How many sales do we actually need to break even?
• Are our goals even feasible at current CPCs?
• What happens to ROAS if we double our budget?

Too often, marketers stay trapped in the comfort zone of ad platform dashboards, looking at metrics like CTR and Quality Score. Forecasting pulls you out of that and demands real-world input - margins, conversion lag, seasonality, and operational constraints.

“Most marketers - including me back in the day - are stuck in the Google Ads interface. We’re thinking about ad metrics, not outcomes.”

Forecasting is how you build the bridge between what the platform says is working and what the business actually needs to succeed. It creates internal accountability, gives clients confidence, and provides a roadmap for scaling that doesn’t rely on guesswork.

And perhaps most importantly, it sharpens that strategic muscle that’s increasingly dulled in a world of one-click AI tools.

“It’s no good copying someone’s prompt off LinkedIn and regurgitating the same stuff. Know what you’re doing - then automate.”

In short, forecasting can feel old-school, but it’s more relevant than ever. It’s your defense against blind automation, and your best tool for turning PPC from an expense into a growth engine.

And when it comes to forecasting, too many marketers are still getting the fundamentals wrong:

Common mistakes in Google Ads forecasting

1. Relying on Google’s Built-In Forecasting Tools

Ed is blunt about the early days of Google’s forecast tools:

“The forecasting was atrocious… You could literally download your live account data, put that keyword data into the forecast tool, and you’d just not get the same results - not even close.”

While Google’s built-in forecasting tools have improved recently, Ed warns that they still lack critical business-level metrics. That means you’re forecasting media metrics like impressions and CPC, but ignoring profitability, margins, or conversion lag.

2. Focusing on Ad Metrics Instead of Business Outcomes

A recurring theme in Ed’s advice is the need to zoom out, and not hyper-focus on the Google Ads interface.

To avoid this, Ed recommends incorporating backend metrics like lead-to-sale conversion rates, return rates for eCommerce, profit margins, and customer lifetime value into your forecasting process.

This is the foundation of Ed’s free forecasting spreadsheet, which allows users to plug in keyword volume data and layer on real-world conversion and profitability assumptions for better projections.

3. Underestimating Seasonality and Demand Curves

If you’re forecasting without accounting for seasonality, you might as well not forecast at all - especially in verticals like retail, travel, education, or event-driven industries. 

Failing to factor in cyclical fluctuations in consumer demand is one of the biggest forecasting missteps marketers make.

Most advertisers instinctively look backwards, pulling data from the last 30 days and projecting it forward. But that’s a surefire way to miss the mark.

The key is to layer historical seasonality trends onto your current performance trajectory. That means comparing year-over-year (YoY) performance by month, identifying patterns in conversion rates, AOV, and impression volume, and using those benchmarks to inform your forecasts for similar time periods ahead.

And seasonality isn’t always obvious. It’s not just Black Friday, back-to-school, or holiday peaks. Even smaller signals - like tax season for financial services, or wedding season for florists - can skew demand substantially.

To handle this uncertainty, Ed recommends building three-scenario forecasts:

• Low-ball - A conservative projection that accounts for performance dips, increased competition, or flat budgets.
• Expected - A realistic forecast based on current trajectory and business-as-usual assumptions.
• Optimistic - A stretch scenario that includes performance uplifts due to campaign improvements, higher budgets, or favorable seasonal bumps.

By modeling a forecast range rather than a single number, marketers can provide clients and stakeholders with a more transparent, strategic, and credible outlook.

“Be very careful with under-egging or overpromising. Some clients will ask for double the conversions on double the spend, but performance isn’t linear. Efficiency often drops as spend increases.”

This is where understanding demand curves becomes crucial. As spend scales, you often reach saturation points where:

• You’re no longer cherry-picking the best leads
• CPCs rise due to increased impression share
• Conversion rates begin to taper

Rather than assuming more budget = more performance, smart forecasters factor in diminishing returns. This is especially important in competitive verticals where scaling means bidding for every click, not just the profitable ones.

Ultimately, accounting for seasonality and demand curves is about balancing ambition with realism, and giving stakeholders the confidence to scale with eyes wide open.

Key components of accurate forecasting

1. Impression share & cost dynamics

Impression share isn’t just a metric - it’s a window into scalability. According to Ed:

“If you’re bidding at 20–30% of available impressions, you’re cherry-picking the best traffic. But at 90%, you’re bidding for every last click - regardless of quality.”

This has a direct impact on CPC. Ed’s spreadsheet allows users to simulate these dynamics by adjusting impression share and observing the resulting cost implications.

His rule of thumb:

• At lower impression shares, CPCs may drop by ~20%.
• At very high impression shares (90%+), expect significant CPC inflation (up to 30–50%).

When forecasting at scale, assume diminishing returns.

“If you’re spending at 20–30% of the available impressions, you’re cherry-picking. But if you’re at 90%, you’re not being selective - you’re taking every click, even the bad ones.”

This means ROAS usually tapers off as spend increases. Forecasts should reflect this reality. Ed’s advice: build a calculator that shows how much more performance is expected per £1,000 spent. Often, clients ask for more than what’s logically deliverable without realizing that extra spend requires disproportionately better efficiency.

2. Remarketing (don’t forget it)

Remarketing spend is often overlooked in forecasts, but it can represent 10% or more of your total ad budget. And with Performance Max now automatically scooping up much of that activity in stealth mode, this gets tricky.

“PMax is spending money on remarketing without you knowing it. And unless you exclude brand, you could be double-counting conversions too.”

Ed suggests allocating ~10% of budget to remarketing unless you’re explicitly managing it with separate RLSA or DSA strategies.

3. Forecasting for high-CPC keywords

If your niche has £30-£50 CPCs, forecasting becomes even more essential. You must know:

• Expected conversion rate
• Value per conversion
• Break-even ROAS

And you have to answer: Can we afford to compete here?

Ed’s spreadsheet helps marketers stress-test these scenarios before any budget is spent, giving confidence in go/no-go decisions.

Forecasting for Performance Max

Performance Max (PMax) is a powerful but opaque tool, and Ed warns that it often inflates performance metrics by funneling easy wins (like branded search) into its results.

“You’ll often see PMax showing a lovely ROAS, but when you break it down, it’s all brand. That’s not net new growth.”

To counteract this:

• Negate brand terms from PMax and run a dedicated brand campaign.
• Use scripts or Google’s new platform/placement reports to audit where PMax is spending.
• Consider Standard Shopping for greater visibility and control.

“Standard Shopping still works gangbusters. Don’t be afraid to go back to it.”

Ed and his colleague Andrew Loke at God Tier Ads often use Standard Shopping to regain visibility over product-level performance and avoid wasting budget on non-converting placements like YouTube or Display.

The trouble with shortcuts

Perhaps the most memorable part of the conversation was Ed’s blunt take on PPC “gurus” and get-rich-quick courses:

“If you’re commenting ‘ROAS’ on the semi-coherent ramblings of an 18-year-old social media guru, you’re going to be disappointed.”

Forecasting well - and managing Google Ads profitably - takes time, reps, and critical thinking. There are no shortcuts.

“Hard work. Mastering something is really rewarding. If you don’t have to put the reps in to be good, we’re all screwed. That means the automation’s so good, we’re irrelevant.”

The role of AI in forecasting (now & future)

AI may streamline ad creation and performance optimization, but Ed is cautious about letting it take over strategic thinking.

“If you’re just using AI to do your forecast - and you don’t know why - it’s a problem. The whole thing of losing critical thinking is frustrating.”

Instead, use AI as a co-pilot, not an autopilot. Understand the variables that impact your forecast (CPC, conversion rate, AOV, seasonality, margin), and then use AI or automation to model scenarios - but never let it replace your judgment entirely.

Final thoughts: Do the work

Ed’s parting message was clear:

“Forecasting is an art as much as a science. It’s not about being perfectly accurate. It’s about being realistic and prepared.”

Building reliable forecasts is what separates hobbyist marketers from strategic operators. If you’re serious about PPC, forecasting isn’t optional. It’s a cornerstone of growth planning, client retention, and budget stewardship.

Download Ed’s forecasting spreadsheet

To apply these lessons immediately, grab Ed’s free Google Ads forecasting sheet here (or visit God Tier Ads directly). The sheet includes:

• Keyword-level forecasting
• Business performance modeling
• Impression share adjustments
• Scenario planning

Ed also has a comprehensive video on his YouTube channel explaining the spreadsheet in additional detail.

If you want to take control of your ad spend - and your results - this is a powerful place to start.

Next steps:

• Follow Ed on LinkedIn - and check out Ed’s website God Tier Ads for a more hands-on approach to improving your paid media skills and advice on how to stay relevant in an automated world.
• Listen to The Paid Media Lab for more actionable insights from leading performance marketers
• Get a free 14-day traffic audit to uncover any hidden inefficiencies in your paid media efforts