Customer Acquisition Cost
Also written CAC · Customer Acquisition Cost (CAC) · Cost of acquiring a customer
The average cost of winning one new customer — read against customer lifetime value, it says whether a start-up is buying revenue at a profit or at a loss.
In plain language
Customer Acquisition Cost measures the average cost of acquiring a new customer. A lower CAC indicates efficient marketing and sales techniques, which can ensure long-term sustainability and scalability.
On its own the number means very little — Rs 600 to win a customer is cheap for a car dealer and ruinous for a Rs 200-a-month app. It becomes meaningful only when set against Customer Lifetime Value (CLTV), the total revenue generated from a customer over the entire relationship with the start-up.
And the workbook is direct about why an investor looks: if the CAC is very high, there are high chances that the start-up would not be able to make profits from its operations.
How it works
CLTV is computed as the average purchase value of customers multiplied by the average number of purchases made by them.
The CLTV/CAC ratio is what allows comparison between two different companies in the same industry. The workbook's illustration: a company with a customer acquisition cost of USD 50 and a lifetime value of USD 250 per new customer has a CLTV/CAC ratio of 5x.
Who uses it and when. Angel investors, investing at the idea and early-product stage, look at CAC and customer lifetime value to measure how much the start-up is spending per customer to get its revenue from that person. Venture capital investors, who come in once there is revenue, are also very cautious while investing in companies with a high CAC, because it hampers long-term growth and sustainability — alongside the MRR and ARR they use to gauge the consistency and sustainability of revenue.
Why it is fragile. CAC is an average over a cohort, and it rises as a company exhausts its cheapest channels. It is also the metric most easily flattered by discounting: a company can cut headline CAC by buying customers who churn, which raises CAC in substance while lowering it on the slide. That is why the ratio, and churn, travel with it.
The formula
CAC = Sales and marketing spend / Number of new customers acquired
CLTV = Average purchase value x Average number of purchases
Ratio = CLTV / CAC
A worked example
Tulsi Direct, a D2C personal-care brand, is raising a Rs 40 crore Series B from a Category II AIF. Its numbers for the year:
Sales and marketing spend Rs 18.00 crore
New customers acquired 3,00,000
CAC 18,00,00,000 / 3,00,000 = Rs 600
Average purchase value Rs 900
Average number of purchases per customer 4
CLTV 900 x 4 = Rs 3,600
CLTV / CAC 3,600 / 600 = 6.0x
At 6x the business looks strong. Then the fund runs the same arithmetic on the most recent quarter, after the brand pushed into a new city with heavy discounting:
Spend in the quarter Rs 9.00 crore
New customers 60,000
CAC Rs 1,500
Average purchases fell to 2.4
CLTV 900 x 2.4 = Rs 2,160
CLTV / CAC 2,160 / 1,500 = 1.44x
The headline annual ratio is 6x; the incremental ratio on the money being spent today is 1.44x. Every new rupee of growth is barely profitable, and the discounting that bought the customers is also what shortened their relationship.
On a Rs 40 crore cheque, that is the difference between funding a machine that turns Rs 1 into Rs 6 and funding one that turns Rs 1 into Rs 1.44 — which is why the fund prices the round off the incremental cohort, not the annual average.
Why NISM asks about it
Chapter 11 section 11.1.2 puts CAC and CLV in the hands of angel and venture capital investors as a screen; Chapter 14 section 14.8.1 lists CAC, CLTV and the CLTV/CAC ratio among the valuation metrics used for start-up valuation and performance assessment. Expect a definition-matching question across the metric list, and a ratio computation.
Common exam traps
- CAC is a cost — lower is better. CLTV is a value — higher is better. Answer options routinely invert one of them.
- The ratio is the comparable number, not CAC alone, and the workbook restricts the comparison to companies in the same industry.
- CLTV in this workbook is average purchase value times average number of purchases. No margin, no discounting — do not import a more elaborate formula into an exam answer.
- Angels look at CAC and CLV at the idea stage; VCs look at CAC alongside MRR and ARR. The workbook assigns the metrics to stages deliberately.
- Churn silently changes CLTV, and therefore the ratio, without CAC moving at all.
- A falling CAC can mean better marketing or a shift to cheaper, worse customers. The metric cannot tell you which.
Where this is taught
Free preparation for NISM Series XIX-DRelated terms
- Cash BurnThe rate at which a start-up spends its cash — set against the money in the bank, it says how many months of runway are left before the next round has to close.
- Churn RateThe percentage of customers who discontinue using a product or service over a given period — the metric that decides whether acquired customers are an asset or a leaking bucket.
- Net Promoter ScoreA customer-loyalty score from a single question — how likely are you to recommend this — computed as the percentage of promoters minus the percentage of detractors.
- Post-money valuationA start-up's pre-money valuation plus the new money going in — the number that fixes what percentage of the company the incoming investor owns after the round.
- Total Addressable MarketThe whole revenue opportunity that exists for a product if every possible buyer bought it — the outermost of the three market-size numbers a venture investor tests a start-up against.
- Serviceable Obtainable MarketThe share of the Serviceable Available Market a company can actually capture in the long run with a sustainable marketing approach — and the number a venture-stage valuation is built on.
- Customer Lifetime ValueThe total revenue a start-up earns from one customer across the whole relationship — average purchase value multiplied by the average number of purchases that customer makes.
- CLTV/CAC ratioCustomer Lifetime Value divided by Customer Acquisition Cost — how many rupees of customer revenue a start-up buys for every rupee it spends winning that customer.