The formula: additional organic visits × conversion rate × average customer value = monthly revenue. Subtract your monthly SEO budget from that revenue for net gain, and the ratio of net gain to budget gives you the ROI percentage.
The critical point with SEO is time: because it is a cumulative channel, cost can run ahead of return in the early months, and as content and authority strengthen the same budget produces steadily more traffic. That is why assessing SEO ROI over a 6 to 12 month window is healthier than looking at a single month. There is another difference from advertising: when spending stops, organic traffic does not drop to zero overnight; the rankings you have earned keep producing revenue for a while.
For the most accurate result, take your conversion rate and customer value from your own analytics. To understand how SEO works more closely, read our Search Engine Optimization (SEO) page, and see where your site stands today with a free SEO analysis.
