LTV:CAC ratio

LTV:CAC is the business-level ratio that determines whether a paid-advertising-driven business model scales profitably. LTV (lifetime value) is total revenue per customer over their lifetime; CAC (customer acquisition cost) is the total sales-and-marketing spend to acquire one customer. The ratio expresses how many times over each customer pays back the cost of acquiring them.

The 3:1 ratio is the canonical benchmark — popularized by SaaS venture capitalists in the 2010s — and remains the working target for most businesses by 2026. Below 3:1, growth is unprofitable at scale: each acquisition consumes more of LTV than the unit economics can sustain. Above 5:1, the business may be under-investing in growth — there's room to acquire more aggressively without breaking unit economics.

Payback period is the companion metric: how many months it takes for cumulative gross profit from an acquired customer to equal CAC. Healthy SaaS targets payback under 12 months; healthy ecommerce targets payback under 90 days. A high LTV:CAC with long payback can still strain working capital.

Both halves of the ratio are hard to measure precisely. LTV requires retention data (churn rate, expansion revenue) and is forward-looking — you're projecting future behavior from historical cohorts. CAC requires correctly attributing every dollar of sales + marketing spend to acquisition vs retention — and most ad-platform attribution is overstated as discussed under ROAS. The practical answer is to compute LTV:CAC quarterly with the best data available and treat it as a directional metric, not a precise one.