How the SEO ROI calculator works
The calculator grows your organic visits evenly from today's level to the growth you expect by the last month. Each month it turns the extra visits into enquiries with your visit-to-enquiry rate, the enquiries into customers with your close rate, and the customers into revenue. Gross margin turns that revenue into profit, which is compared with what you spend on SEO.
Every input is yours. I have not built in benchmark conversion rates or "average" SEO results, because they vary too much between markets to be useful. If you do not know a number, use your analytics and your CRM: visits from Google organic, enquiries from those visits, and how many became customers.
Reading the result honestly
- Growth is the uncertain input. Run the calculator three times: a cautious, a likely and an ambitious growth figure. If only the ambitious case pays back, the plan needs a narrower focus.
- Payback usually lags. SEO work compounds, so early months cost more than they return. The payback month shows when the cumulative profit catches up with the cumulative spend.
- Lifetime value matters. If customers buy again, use first-year revenue or a cautious lifetime figure rather than one order.
If you want a forecast built from your real data instead of round numbers, that is part of an SEO audit: I size the opportunity per page and per query before recommending any spend.