Free Guide
Digital Marketing ROI Calculator: Formulas & Worked Example
You do not need special software to know whether marketing is paying off. Gather five numbers, apply the formulas below and you can compare any channel on equal terms. The worked example uses illustrative figures, not results we are promising.
1. The core formulas
ROI % = (Revenue − Marketing cost) ÷ Marketing cost × 100
ROAS = Revenue ÷ Ad spend (a ROAS of 4 means ₹4 back for every ₹1 spent)
CPL = Marketing cost ÷ Number of leads
Conversion rate % = Conversions ÷ Visitors × 100
CAC = Total marketing cost ÷ New customers won
Payback period = CAC ÷ Monthly gross profit per customer
2. Worked example: a Google Ads campaign (illustrative)
Ad spend for the month: ₹50,000, producing 1,000 clicks at an average ₹50 per click
5% of visitors enquire: 1,000 × 5% = 50 leads, so CPL = ₹1,000
10% of leads become customers: 50 × 10% = 5 customers, so CAC = ₹10,000
Average order value ₹40,000: 5 × ₹40,000 = ₹2,00,000 revenue
ROAS = ₹2,00,000 ÷ ₹50,000 = 4.0
ROI = (₹2,00,000 − ₹50,000) ÷ ₹50,000 × 100 = 300%
3. Measuring SEO ROI
SEO takes months to compound, so measure it over 6–12 months rather than month by month
Count the full cost: retainer or salaries, content, tools and development time
Only count revenue you can tie to organic search, using GA4 conversions and a CRM source field
Track leading indicators too: impressions, average position and clicks in Search Console
Compare the cost per organic lead with your paid cost per lead to see the true blended picture
4. Numbers to collect before you calculate
Total spend per channel, including agency fees and creative costs
Leads per channel from GA4 events, call tracking and form submissions
Lead-to-customer close rate from your CRM or sales team
Average order value or average deal size
Gross margin, because ROI on revenue overstates the real return
5. Common ROI mistakes
Judging a channel on last-click credit alone and ignoring assisted conversions
Comparing revenue with spend when profit is what pays the bills
Stopping a campaign before it has enough data to judge (aim for at least 30 conversions)
Forgetting offline conversions such as phone calls and WhatsApp chats
Ignoring lifetime value for repeat-purchase businesses, which makes good channels look expensive
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