Free Customer Acquisition Cost (CAC) Calculator with Payback Period

Customer Acquisition Cost (CAC) is the average amount you spend to win one new customer. It is the core unit-economics number: if you cannot acquire customers for less than they are worth, the business does not scale.

The formula:

CAC = (Marketing spend + Sales spend) / New customers

Add up all sales and marketing costs for a period, then divide by the number of new customers from that same period.

Worked example: $10,000 in ad spend and tools, plus $0 sales spend, acquiring 200 new customers, gives a CAC of $50.

Include ad spend, agency fees, marketing software, content costs, and any sales salaries or commissions. Match the spend window to the customer window so the two line up.

There is no single "good" CAC number, because a $50 CAC is excellent for a store with a $500 lifetime value and unworkable for one with a $60 lifetime value. Judge CAC against two yardsticks instead of an industry average:

• LTV:CAC ratio. Around 3:1 is the working standard for sustainable growth. Check yours with the CLV calculator.
• Payback period. Ecommerce and DTC brands often aim to recover CAC within 6 months, and under 12 months is a common healthy benchmark.

So a CAC is "good" when your margins and repeat purchases earn it back quickly.

The CAC payback period is how long it takes to earn back what you spent acquiring a customer, measured from their gross profit.

Payback period = CAC / Monthly gross profit per customer

Ecommerce and DTC brands often target under 6 months, with under 12 months considered healthy (Stripe, Corporate Finance Institute). The faster you recover CAC, the less cash you tie up funding growth, which matters most for lean early-stage stores.

Blended CAC divides total spend by all new customers, including the ones who arrived through organic search, referrals, and direct. Paid CAC divides paid spend by only the customers that paid channels brought in.

Blended CAC tells you the true cost of growth across the whole business. Paid CAC tells you whether a specific channel is profitable. Track both: a healthy blended number can hide an unprofitable paid channel that organic is quietly subsidizing.

CPA (cost per acquisition) is the cost of any defined conversion, which could be a lead, a signup, or an add to cart. CAC (customer acquisition cost) is narrower: the cost of acquiring a paying customer.

Every CAC is a CPA, but not every CPA is a CAC. For unit economics and budgeting, CAC is the number that matters, since only paying customers generate revenue to offset the spend.

Two routes: spend more efficiently, or convert more of the traffic you already pay for.

1. Lift conversion rate. Every extra percentage point of conversion lowers CAC without extra ad spend. The Shopify CRO guide covers the patterns, and a free store audit surfaces the friction.
2. Improve ad efficiency. Track ROAS by channel and cut the underperformers. Compare against ROAS benchmarks by industry.
3. Grow organic and retention. Organic traffic and repeat customers carry a near-zero marginal CAC, which pulls your blended number down.

Both move the same ratio, so work the cheaper lever first. Lowering CAC has a floor, since you can only get acquisition so efficient. Raising lifetime value through retention, higher average order value, and repeat purchases often has more room.

A higher lifetime value also lets a higher CAC stay healthy, which means you can outbid competitors for the same customer. Check where you stand with the CLV calculator and the LTV:CAC ratio.