Customer Acquisition Cost (CAC) Calculator
CAC (Customer Acquisition Cost) is your total sales and marketing spend divided by the number of new customers acquired in the same period. It answers 'how much am I paying to win a new customer?' - the single most important efficiency metric in ecommerce.
CAC (Customer Acquisition Cost) is your total sales and marketing spend divided by the number of new customers acquired in the same period. It answers 'how much am I paying to win a new customer?' - the single most important efficiency metric in ecommerce.
CAC = Marketing Spend ÷ New Customers
- CAC tells you whether growth is profitable - a 3× ROAS with a rising CAC still means the business is getting worse.
- LTV:CAC below 1 means you lose money on every new customer; below 3 means growth is fragile.
- Investors and lenders benchmark ecommerce businesses on CAC and payback period, not vanity revenue.
- Lift repeat-purchase rate - the fastest way to raise LTV without touching acquisition.
- Move budget from broad prospecting to retention (email/SMS, ads to existing customers).
- Invest in SEO and referral: near-zero marginal CAC once ranking and word-of-mouth compound.
- Improve landing-page and checkout CVR - same spend, more customers, lower CAC.
- Cut spend on channels where blended CAC exceeds first-order gross profit for 30+ days.
CAC Calculator - questions founders ask
There is no single number - a good CAC is any CAC where LTV divided by CAC is at least 3 and payback happens within 6-12 months. A £15 CAC on a £30 candle is fine only if the customer buys again; a £150 CAC on a £2,000 mattress is fine if margin covers it in one order.
Want the operator team behind these numbers?
BeingEcom runs Ecommerce Analytics & Attribution for UK Shopify and WooCommerce brands. Book a free strategy call and we'll model the same numbers against your real store.