How do you calculate customer acquisition cost?

Divide acquisition spend by the new customers it won in the same period. Which spend and which customers depends on the question: all sales and marketing over all new customers gives blended CAC; paid media over paid-acquired customers gives paid CAC; the change in spend over the change in customers gives marginal CAC.

What is the difference between blended CAC and paid CAC?

Blended CAC spreads total sales and marketing spend across every new customer, including those who arrived through organic search, referral or word of mouth for free. Paid CAC counts only paid media and only the customers it bought. Blended is almost always lower, which is why it flatters a young brand.

Why is marginal CAC higher than average CAC?

Paid channels saturate. The auction reaches your cheapest, most likely buyers first, so each extra dollar buys attention from colder, pricier audiences. In the example on The Math, the average across five spend tranches is about A$82 while the fifth tranche costs A$263 per customer.

What is a good customer acquisition cost?

One below what the customer returns in contribution margin, inside a payback window your cash can fund. A dollar figure means nothing on its own: an A$150 CAC can be healthy on a high-repeat product and ruinous on a one-off purchase. Check yours with the blended CAC and LTV:CAC calculator.

Customer acquisition cost: the three CACs, worked

The formula

Same shape, three different numerators and denominators.

Every CAC is spend divided by customers. What changes is which spend and which customers.

Term	What it means
Blended CAC	Total sales and marketing spend ÷ all new customers, from every channel, paid or not. Answers: how efficient is the whole engine? See blended CAC.
Paid (new-customer) CAC	Paid media spend ÷ new customers acquired through paid. Answers: is paid acquisition sustainable, and how do we compare with peers? See new-customer CAC.
Marginal CAC	Δ spend ÷ Δ new customers between two spend levels. Answers: should the next dollar go in? See marginal CAC.

The first two divide a total by a total and give an average. The third divides a change by a change and gives a slope. On a paid channel that is saturating, the slope sits above the average, because the auction reaches your cheapest, most likely buyers first and each extra dollar reaches a colder audience.

One store, one month

Three honest CACs from the same spend.

A store spends A$120,000 on sales and marketing: A$90,000 of paid media and A$30,000 of agency, content and tools. It wins 1,500 new customers, 900 of them through paid. Last month, paid spend was A$75,000 and paid won 790.

Worked example / demonstrative numbers

Blended CAC: A$120,000 ÷ 1,500 new customersA$80

Paid CAC: A$90,000 ÷ 900 paid customersA$100

Extra paid spend this month: A$90,000 − A$75,000A$15,000

Extra paid customers: 900 − 790110

Marginal CAC: A$15,000 ÷ 110A$136

All three are correct. The board hears A$80 and assumes the next customer costs A$80. The last A$15,000 actually bought customers at about A$136 each (A$136.36 unrounded). Whether that was worth it depends on what those customers return in margin, not on the A$80.

The Math's example

A$82 on average, A$263 at the margin.

The demonstrative channel published on The Math and in the three CACs: five A$50,000 spend tranches, each buying customers at a higher cost than the last. Customer counts are derived from the published tranche costs and rounded.

Worked example / demonstrative numbers

Tranche 1, first A$50k: ≈1,190 customersA$42 each

Tranche 2, to A$100k: ≈820 customersA$61 each

Tranche 3, to A$150k: ≈521 customersA$96 each

Tranche 4, to A$200k: ≈316 customersA$158 each

Tranche 5, to A$250k: ≈190 customersA$263 each

Average across all five: A$250,000 ÷ 3,037A$82

Same account, same month. Report the A$82 and scale on it, and you walk straight into the A$263 customers. If a new customer's first-order margin is well under A$263, the fifth tranche is losing money while the average still looks fine.

Which CAC for which decision

Pick the question, then the number.

Decision	Use	Why not the others
Is the whole go-to-market efficient?	Blended CAC	Paid CAC ignores the organic and referral customers your total spend also pays for.
How do we compare with other brands?	Paid CAC	Published benchmarks are mostly built on paid-acquired customers; blended flatters a brand with strong organic.
Should we add budget to this channel?	Marginal CAC	Both averages lag the rising cost of the next customer.
How long is cash tied up per customer?	Paid or marginal CAC, over monthly margin	CAC alone says nothing about time. Use CAC payback.

Common mistakes

Where customer acquisition cost goes wrong.

Quoting CAC without saying which.The same brand can honestly report numbers several times apart. Label every CAC with its definition.
Scaling on the average.Average CAC drifts up gently while marginal CAC climbs fast. Compute the slope before every budget change.
Counting customers from platform conversions.Platforms over-claim, so the customer count in the denominator is inflated. See platform over-claiming.
Judging CAC without margin.A CAC is only good or bad against what the customer returns. Hold it against margin LTV and payback.

How Blufire automates it

All three CACs, per channel and cohort, in margin.

Section S2, Unit Economics, tracks new-customer CAC and CM-payback per acquisition cohort, and Marginal CAC & Saturation shows where the next dollar of spend on each channel stops paying. The Payback Waterfall turns that into months to breakeven, cohort by cohort.

At the top of the product, the executive Portfolio Headline carries blended MER and CM payback, the time for CM1 to recover acquisition cost, next to revenue and contribution margin.

Cohort economicsNew-customer CAC and CM-payback per acquisition cohort, in margin rather than revenue.
Marginal CAC & SaturationWhere each channel's next dollar stops buying customers profitably.
Payback WaterfallMonths to breakeven, cohort by cohort.
Portfolio HeadlineBlended MER and CM payback beside net revenue and CM1.

See section S2, Unit Economics→

S1 Executive · Portfolio Headline