Divide your total monthly SEO investment by the measurable business outcome it drives. If you spend $3,500/month on SEO and it generates $28,000 in attributed organic revenue, your cost efficiency is 12.5% (or an 8:1 return). For lead-gen businesses, divide spend by qualified leads, then multiply by your close rate and average deal value to get cost per acquisition. The challenge is attribution. Set up proper tracking in Google Analytics 4 with UTM-free organic session tagging, and use Search Console to identify which landing pages drive conversions. Compare your organic CAC against paid search, paid social, and other channels. SEO typically underperforms in months 1–4, breaks even around month 5–7, then outperforms by 40–70% as compounding kicks in. Track these metrics monthly: - Organic revenue or qualified leads from non-branded queries - Total SEO spend including agency fees, content costs, technical work, and internal time - Assisted conversions where organic was in the path but not last-click - Opportunity cost of ranking position 4 versus position 1 on your money keywords Ottawa SEO Inc. runs monthly efficiency reports for retained clients comparing SEO cost per lead against their Google Ads benchmarks. We typically see SaaS and service clients hit 1:5 return ratios by month 9, while ecommerce can hit 1:8 or better by month 12 due to category page compounding. Local service businesses with sub-$2,000 monthly budgets often see breakeven faster because maps rankings move quicker than organic. The mistake most businesses make is killing SEO investment right before the compounding phase kicks in. If your CAC is still 20% higher than paid channels at month 5, that's normal. If it's still higher at month 11, either your keyword targeting is wrong or your conversion paths need work. Cost efficiency in SEO is a trailing indicator, not a leading one.