LTV:CAC Ratio Explained: Formula, Example, and Interpretation

What the LTV:CAC ratio is

The LTV:CAC ratio compares how much a customer is worth over their lifetime (customer lifetime value, or LTV) against how much it cost to acquire them (customer acquisition cost, or CAC). It is a single number, expressed as a ratio such as 3:1, that shows how many dollars of value a customer returns for every dollar spent acquiring them.

Formula

LTV:CAC ratio = LTV ÷ CAC

That is the entire calculation. Almost all of the judgment involved in LTV:CAC is in how LTV and CAC are each measured before this division — not in the division itself.

Worked example

A subscription business measures one customer cohort as follows:

• Average monthly revenue per customer = $200
• Gross margin = 75%
• Monthly churn rate = 5%
• Customer acquisition cost (CAC) = $1,000

Expected customer lifespan = 1 ÷ 5% = 20 months
Revenue LTV = $200 × 20 = $4,000
Gross-profit LTV = $4,000 × 75% = $3,000
LTV:CAC ratio (gross-profit basis) = $3,000 ÷ $1,000 = 3.0, or 3:1

Try this scenario yourself on the Customer Lifetime Value Calculator, the Customer Acquisition Cost Calculator, or run both sides at once on the LTV:CAC Ratio Calculator.

What the ratio does and does not tell you

The ratio tells you the size of estimated lifetime value relative to acquisition spend for the cohort and period you measured — nothing more. It does not tell you:

• Timing. LTV:CAC has no sense of when the value arrives. A 3:1 ratio spread evenly over five years behaves very differently for cash flow than the same 3:1 recovered in the first three months. That timing question is answered by CAC payback period, a separate calculation this ratio does not replace.
• Net profit. LTV minus CAC, or their ratio, is not net profit. Both figures typically exclude fixed overhead, taxes, discounting of future cash flows to present value, and refunds.
• Whether the underlying LTV and CAC estimates are accurate. The ratio is only as reliable as the two inputs. An optimistic LTV assumption (churn that's lower than reality, a lifespan that's longer than reality) or an incomplete CAC figure (marketing spend without sales cost) will produce a ratio that looks healthy without being real.

Gross-profit basis vs revenue basis

LTV can be expressed on a revenue basis (total revenue expected from the customer) or a gross-profit basis (that revenue after subtracting the cost of delivering the product or service). Both are valid ways to label the same LTV ÷ CAC arithmetic — switching basis does not change the formula, only which number you feed into it. In the worked example above, using revenue LTV instead of gross-profit LTV would give $4,000 ÷ $1,000 = 4.0, a higher ratio for the same customer, because revenue LTV has not been reduced by delivery cost. Gross-profit basis is generally more decision-useful for comparing against CAC, since CAC is a real cash outlay and revenue LTV alone can overstate what a customer is actually worth to the business. Whichever basis you choose, state it explicitly next to the ratio so it isn't compared against a differently-measured ratio elsewhere.

Target ratios: a factual comparison, not a universal rule

A commonly cited planning reference in SaaS discussions is a 3:1 ratio, but this is a rule of thumb, not a measured law — it is not sourced from a single authoritative benchmark, and this site does not treat it as universally correct. Whether a given ratio is adequate depends on your margin structure, cash position, CAC payback period, growth stage, retention quality, and how rigorously LTV and CAC are each measured. A ratio below 1:1 means measured acquisition cost exceeds measured lifetime value — worth understanding why, but not automatically a failure if it reflects an early, deliberately loss-leading growth stage. A very high ratio (10:1 or more) is not automatically good either; it can just as easily indicate under-investment in growth as it can indicate efficiency.

Cohort interpretation

LTV and CAC should describe the same cohort over comparable time windows, using consistent definitions for both. Pairing an LTV estimate built from one acquisition cohort or period with a CAC figure from a different one produces a ratio that looks precise but does not correspond to any real group of customers. When retention curves, acquisition channels, or expansion revenue vary meaningfully across cohorts — for example, customers acquired through paid ads versus referrals, or customers from different sign-up quarters — a single blended LTV:CAC ratio can hide that variation. Calculating the ratio per cohort, rather than only as one company-wide average, shows whether some cohorts are far more efficient to acquire than others.

Limitations and common mistakes

• Mismatched time periods. Combining a monthly churn rate with an annual revenue figure (or vice versa) in the LTV calculation produces a lifespan and LTV that don't correspond to any real period.
• Treating the ratio as a guarantee. LTV is a forward-looking estimate built on assumptions about future churn and revenue; actual customer behavior can diverge from those assumptions.
• Ignoring CAC payback period. A strong LTV:CAC ratio does not guarantee a short payback period — a business can have both a healthy ratio and a cash-flow problem if value is recovered too slowly.
• Double-counting or omitting cost. Leaving sales cost out of CAC (marketing spend only) inflates the ratio; including unrelated overhead in CAC deflates it.