Customer Acquisition Cost (CAC)

CAC (customer acquisition cost) is the total sales and marketing spend a business incurs in a period, divided by the number of new customers it gains in that same period. CAC tells you how much each new customer is costing you.

What is CAC?

Unlike ad spend, CAC counts every cost of winning new customers. HubSpot lists the usual items: content production, social media, ad budget, sales salaries and commissions, and software (HubSpot, October 2025). For a real estate company, brokerage fees paid to agents also count toward CAC. For an app, it can include referral bonuses or vouchers for new users.

Define “new customer” clearly before you calculate: someone who placed a first order, a student who has paid tuition, or an app user who has paid for the first time. A lead or an app install is not a customer yet.

CAC formula

CAC = Total sales and marketing costs in the period / Number of new customers in the period

Andreessen Horowitz (a16z) separates two ways to calculate it (a16z, 16 Startup Metrics, August 2015):

• Blended CAC: total acquisition cost divided by all new customers, including those who found you on their own.
• Paid CAC: acquisition cost divided by the new customers who came from paid channels.

In a16z’s view, blended CAC is not wrong, but it does not tell you whether your advertising is profitable. Paid CAC answers the question of whether the business can raise ad spend and still make money. The article also points out a common mistake: leaving out referral fees, credits or discounts given to new customers.

CAC and LTV

CAC only means something next to LTV, the value a customer brings in over the whole time they keep buying. HubSpot suggests an LTV:CAC ratio of about 3:1 and earning back acquisition cost within one year. A ratio near 1:1 means a customer is worth only what you paid to get them. A ratio well above 3:1 may be a sign you are spending too little on growth. These are reference points, not a standard for every industry.

CAC vs. CPA vs. CPI

A campaign with a very cheap cost per lead can still end up with a high CAC if the sales team closes only a few of those leads.

Example in Vietnam (hypothetical)

In Q3, an English language center in Ho Chi Minh City spends 300 million VND on ads, 120 million VND on advisor salaries and commissions, and 30 million VND on CRM and call center software, for a total of 450 million VND. That quarter it signs up 150 new students who pay tuition: 100 came from ads and 50 were referred by former students.

• Blended CAC = 450,000,000 / 150 = 3 million VND.
• Paid CAC = 450,000,000 / 100 = 4.5 million VND.

If each student pays 12 million VND on average at a 50% gross margin, each one brings in about 6 million VND of gross profit. With a paid CAC of 4.5 million VND, the ratio is only about 1.3:1. Raising the ad budget right now is less safe than improving the close rate or getting more referrals.

Frequently asked questions

Should you calculate CAC monthly or quarterly?

Quarterly is usually more stable, especially when the decision cycle is long, as in real estate, education and B2B. Monthly figures skew easily, because this month’s spend can bring in customers next month.

Does a rising CAC mean the ads are bad?

Not necessarily. CAC can rise because of peak season ad prices, changes in the sales team, or because the easy-to-close customers have run out. Break CAC down by channel and by funnel stage before drawing conclusions.

If you want to recalculate CAC by channel to see where to raise or cut budget, Adtek’s Lead Generation and App User Acquisition teams can go through the numbers with you via our contact page.