How to Calculate & Improve Your Google Ads ROAS

What Is ROAS and Why Does It Matter?

Return on Ad Spend (ROAS) is the single most important metric for measuring Google Ads profitability. It tells you how much revenue you earn for every pound you spend on advertising.

The formula is simple: ROAS = Revenue from Ads / Cost of Ads. If you spend £1,000 on Google Ads and generate £5,000 in revenue, your ROAS is 5:1 (or 500%).

But here's what most advertisers get wrong — they treat ROAS as a vanity metric rather than a decision-making tool. Your ROAS should directly inform how you allocate budget, which campaigns to scale, and which to pause.

A 4x ROAS doesn't mean you're profitable. If your margins are 20%, you're breaking even. ROAS only matters in context of your unit economics.

How to Calculate Your Google Ads ROAS

Calculating ROAS seems straightforward, but there are nuances that trip up even experienced advertisers.

Basic ROAS Calculation

Pull your conversion value and cost data from Google Ads. The platform calculates this automatically in the Conv. value / cost column. But be careful — this figure is only as accurate as your conversion tracking.

True ROAS vs Reported ROAS

Google Ads reports ROAS based on attributed conversions, which may not match your actual bank deposits. Common discrepancies include:

• Returns and cancellations — Google counts the sale, not the refund
• Attribution window — a 30-day click window may over-count conversions
• Cross-device gaps — some conversions aren't tracked
• Offline conversions — phone calls and in-store visits often go untracked

To get your true ROAS, compare your Google Ads spend against actual revenue in your accounting system over the same period. This is your "blended ROAS" and it's the number that actually matters.

ROAS Benchmarks by Industry

Benchmarks are useful as a sanity check, but your target ROAS should be based on your margins, not someone else's results.

These are Search campaign benchmarks. Shopping and Performance Max campaigns typically run 20-40% higher ROAS due to stronger purchase intent.

How to Set Your Target ROAS

Your target ROAS should be based on your break-even point, not industry averages. Here's how to calculate it:

1. Calculate your profit margin — If your average order is £100 and your cost of goods + fulfilment is £60, your margin is 40%
2. Find your break-even ROAS — Divide 1 by your margin: 1 / 0.40 = 2.5x. At 2.5x ROAS, you break even on every sale
3. Add your profit target — If you want a 20% net margin on ad spend, your target ROAS is approximately 3.5x
4. Factor in lifetime value — If customers reorder 3x on average, you can afford a lower initial ROAS

When to Accept Lower ROAS

Lower ROAS isn't always bad. It makes sense when you're acquiring customers with high lifetime value, entering a new market, or building brand awareness that drives future organic traffic. The key is knowing why your ROAS is lower and having a plan to improve it.

6 Proven Strategies to Improve ROAS

1. Fix Your Conversion Tracking First

You can't optimise what you can't measure. Before tweaking campaigns, ensure your conversion tracking is set up correctly. Implement enhanced conversions, set appropriate attribution windows, and use offline conversion imports if you have a sales cycle.

2. Eliminate Wasted Spend with Negative Keywords

Most accounts waste 20-40% of their budget on irrelevant search terms. Review your search terms report weekly and add negatives aggressively. This is the fastest way to improve ROAS without spending more.

3. Restructure Around Profitability

Segment campaigns by product margin, not just product category. A £10 product and a £200 product shouldn't share the same ROAS target. Create separate campaigns for high-margin and low-margin products with different bid strategies.

4. Optimise Landing Pages for Conversion

A 1% improvement in conversion rate can dramatically lift ROAS without any changes to your ads. Focus on page speed (under 3 seconds), clear value proposition above the fold, social proof, and a frictionless checkout process.

5. Use Smart Bidding Strategically

Target ROAS bidding works well with sufficient conversion data (30+ conversions in 30 days). Start with a target slightly below your actual ROAS to let Google's algorithm learn, then gradually increase it. Avoid setting targets too aggressively — the algorithm will restrict volume.

6. Scale What Works, Cut What Doesn't

Review performance at the campaign, ad group, and product level. Shift budget from underperforming campaigns to your top performers. This sounds obvious, but most advertisers let poor campaigns run indefinitely because "they might improve."

Common ROAS Mistakes to Avoid

Even experienced advertisers fall into these traps:

• Optimising for ROAS at the expense of volume — A 10x ROAS on £100 spend is worse than 4x on £10,000
• Ignoring attribution lag — Don't judge yesterday's campaigns by yesterday's revenue. Allow for your typical conversion delay
• Using the same target across all campaigns — Brand campaigns naturally have higher ROAS. Non-brand prospecting will be lower. Both are necessary
• Chasing ROAS over profit — A high ROAS with tiny volume can produce less total profit than moderate ROAS at scale
• Not accounting for seasonality — ROAS fluctuates naturally. Compare year-on-year, not week-on-week

How to Track ROAS Effectively

Tracking ROAS properly requires looking at multiple levels and timeframes:

Daily Monitoring

Check for anomalies — sudden drops in conversion rate, spend spikes, or tracking issues. Don't make changes based on daily data, but flag anything unusual for investigation.

Weekly Reviews

Review campaign-level ROAS, search term reports, and budget allocation. This is where most optimisation decisions should happen.

Monthly Analysis

Compare blended ROAS (Google Ads spend vs actual revenue) at the account level. Reconcile with your finance data. Evaluate whether your ROAS targets are still appropriate given any changes in margins or business goals.

Building a ROAS Dashboard

Create a simple spreadsheet or Looker Studio dashboard that tracks: total spend, attributed revenue, blended revenue, ROAS by campaign type (brand vs non-brand vs shopping), and month-over-month trends. This gives you the full picture that Google Ads alone can't provide.

ROAS vs ROI: Understanding the Difference

ROAS and ROI are often confused, but they measure fundamentally different things.

ROAS is a top-line metric: Revenue / Ad Spend. It doesn't account for product costs, agency fees, or overhead. A 4x ROAS means you made £4 in revenue for every £1 spent on ads.

ROI is a bottom-line metric: (Profit - Total Investment) / Total Investment. It includes everything — product costs, ad spend, agency fees, shipping, and operational overhead.

You need both. ROAS tells you how efficient your advertising is. ROI tells you if the whole operation is actually making money. A campaign with excellent ROAS can still have negative ROI if your margins are thin enough.