Updated on 9 November 2026 by Nicolas Finet, CEO of Sortlist. This guide has been rewritten for 2026: it explains how to calculate marketing ROI correctly (and how it differs from ROAS), how to track conversions under UK consent rules, how GA4 attribution works, and how to go beyond last-click with incrementality tests.
Return on investment (ROI) tells you whether a campaign made money. It sounds simple, but results depend on what you count as revenue, what you count as cost and how you attribute sales to channels. This guide shows a practical way to measure it, step by step.
Key takeaways
- ROI uses profit, not revenue: a 5:1 revenue-to-spend ratio (ROAS) is not 500% ROI. At a 60% gross margin, it produces a 200% return before other operating costs.
- GA4 offers data-driven attribution by default, plus last-click options; first-touch, linear, time-decay and position-based models were removed in 2023.
- For a more honest picture of what campaigns caused, add incrementality tests and marketing mix modelling to platform reporting.
ROI vs ROAS
| Measure | Formula | Question answered |
|---|---|---|
| ROAS (return on ad spend) | Revenue from ads ÷ ad spend | How much revenue per £1 of ads? |
| Marketing ROI | (Gross profit from marketing − marketing cost) ÷ marketing cost × 100 | Did marketing make a profit, and how much per £1? |
“A 5:1 revenue-to-cost ratio is not automatically 500% profit ROI: at a 60% gross margin it produces a 200% return before other operating costs.”
Konabayev, Marketing ROI (2026)
Example (hypothetical): you spend £10,000 on a campaign and it generates £50,000 in revenue (ROAS 5:1). With a 60% gross margin, gross profit is £30,000. ROI = (£30,000 − £10,000) ÷ £10,000 = 200%.
Step 1: define objectives and KPIs
Identify specific goals
Choose one primary goal: sales, qualified leads, bookings, sign-ups or awareness. Awareness campaigns are harder to measure with ROI, so use proxy measures such as branded search and brand-lift surveys.
Determine KPIs aligned with objectives
| Goal | Primary KPIs |
|---|---|
| Sales | Revenue, gross profit, ROAS, cost per acquisition |
| Leads | Cost per lead, lead quality, conversion to customer |
| Awareness | Reach, frequency, branded search, brand lift |
| Retention | Repeat rate, lifetime value, churn |
Step 2: track conversions
Set up conversion tracking
Use Google Analytics 4 events marked as key events, platform pixels and your CRM or ecommerce data. Give conversions values where possible. Test tracking before launch and check it against real orders.
Define what a conversion is
Purchases, sign-ups, calls, form submissions or downloads. Separate macro conversions (sales) from micro conversions (add to basket) and use each in the right place.
UK consent and data quality
Advertising and tracking cookies generally need consent in the UK, which means some conversions are not observed. Use consent mode and modelled conversions where appropriate, and reconcile with first-party data such as orders and CRM records. See web analytics tools.
Step 3: calculate the cost of the campaign
- Media spend: ads, sponsorships, influencer fees.
- Creative and production: design, video, copy.
- Tools and platforms: software, analytics, testing.
- People and agency fees: internal time and external costs.
- Other costs: discounts given, free shipping, commissions to partners.
Counting only media spend overstates ROI. Use the full cost.
Step 4: attribute revenue
Attribution decides which touchpoints get credit for a sale. In GA4, the default reporting attribution model is data-driven attribution, with last-click options available. Google removed first-touch, linear, time-decay and position-based models from GA4 in late 2023. Platforms such as Google Ads and Meta also report their own attributed conversions, which can overlap, so totals across platforms often exceed real sales.
- Compare platform-reported conversions with your own order and CRM data.
- Use UTM parameters consistently.
- Look at assisted conversions, not only last click.
- Allow for the time between first interaction and purchase.
Step 5: calculate and interpret ROI
- Total the revenue attributed to the campaign.
- Convert to gross profit using your margin (and include returns and refunds).
- Subtract total campaign cost.
- Divide by cost and multiply by 100.
Choose one convention and use it consistently when comparing campaigns. Compare ROI with your required return and cash payback period: a campaign with positive ROI but slow payback may still strain cash.
Step 6: measure what the campaign caused
Attribution shows which touchpoints were present, not what changed behaviour. Some sales would have happened anyway, such as brand searches and existing customers. To measure incremental impact:
- Geo holdouts: switch advertising off or down in some regions and compare results.
- Platform lift studies: randomised tests offered by ad platforms.
- Marketing mix modelling: statistical models that estimate each channel's contribution; open-source tools include Meta's Robyn and Google's Meridian.
See how to create an advertising campaign for more on measurement approaches.
Step 7: analyse and optimise
- Compare ROI by channel, campaign, audience and creative.
- Shift budget from low to high performers, allowing for diminishing returns.
- Check customer quality and lifetime value, not only first-purchase ROI.
- Improve conversion rates; see conversion rate optimisation.
- Document lessons for the next campaign.
Common mistakes
- Using revenue instead of profit.
- Ignoring non-media costs.
- Trusting platform-reported conversions without checking.
- Measuring too early for long sales cycles.
- Giving brand campaigns the same short-term ROI test as promotions.
- Comparing figures calculated with different formulas.
Frequently asked questions about campaign ROI
What is the formula for marketing ROI?
(Gross profit from marketing − marketing cost) ÷ marketing cost × 100.
What is the difference between ROI and ROAS?
ROAS is revenue divided by ad spend. ROI uses profit and full cost.
What is a good marketing ROI?
It depends on margins, payback period and goals. A 5:1 revenue ratio is often quoted, but it does not by itself mean a profitable 500% ROI.
Which attribution model does GA4 use?
Data-driven attribution by default, with last-click options for paid and organic channels or Google paid channels.
How can I measure incremental impact?
Use geo holdouts, lift studies and marketing mix models alongside attribution.
How long should I wait to measure ROI?
At least one full buying cycle for your product, and longer for high-consideration purchases.
Need help measuring campaign performance? Post your project on Sortlist and compare UK analytics and marketing agencies for free.
Sources: Konabayev, Marketing ROI, Marketful, Marketing ROI, Polar Analytics, GA4 attribution models, Mbuzz, GA4 models removed. The worked example is hypothetical.
