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Excel guide · 4 min read

How to calculate customer acquisition cost in Excel

Quick answerCustomer acquisition cost (CAC) = what you spent to win customers / the number of new customers in the same period. In Excel: =SUM(C2:C10)/SUM(D2:D10). Here $6,900 of ad spend brought 197 new customers, a blended CAC of about $35.03.

Sample data

Every result on this page was calculated from this sheet by the same spreadsheet engine the Cellwise app uses.

ABCDEFG
1MonthChannelSpendNew customersSettingValue
2Aug 1, 2026Paid social120030Other monthly costs (tools, freelancers)450
3Aug 1, 2026Search ads90018Monthly revenue per customer18
4Aug 1, 2026Organic012Gross margin (yours)0.6
5Sep 1, 2026Paid social135027Customer lifetime value180
6Sep 1, 2026Search ads95025MonthOct 1, 2026
7Sep 1, 2026Organic015
8Oct 1, 2026Paid social150025
9Oct 1, 2026Search ads100026
10Oct 1, 2026Organic019

Download this sheet as an Excel practice file (.xlsx)

Blended CAC: all spend over all new customers

Keep one row per month and channel: the month, the channel, what you spent and how many new customers it brought. That shape makes every other view a SUMIFS away.

Blended CAC divides everything you spent by every new customer, including the ones who found you on their own. It's the number that tells you what growth cost the business overall. Over three months: $6,900 / 197 = $35.03.

=SUM(C2:C10)/SUM(D2:D10)

Result: 35.025380711 shows as $35.03 with Currency format

About 35.03: $6,900 / 197 new customers.

Paid CAC: leave out the free customers

The 46 organic customers cost no ad money, so they pull blended CAC down. To judge whether ads pay off, divide paid spend by the customers the paid channels brought. "<>Organic" means "not equal to Organic".

Paid CAC here is $45.70, about 30% higher than blended. Use paid CAC to decide ad budgets, and blended CAC to describe the business. Mixing them is how a team ends up scaling ads that only looked cheap because word of mouth was doing the work.

=SUMIFS(C2:C10,B2:B10,"<>Organic")/SUMIFS(D2:D10,B2:B10,"<>Organic")

Result: 45.695364238

About 45.70: $6,900 of paid spend / 151 paid customers.

CAC by month and by channel

Add a month test to both SUMIFS. With the month in G6, =SUMIFS(C2:C10,A2:A10,G6)/SUMIFS(D2:D10,A2:A10,G6) gives October's blended CAC: $2,500 / 70 = $35.71. That barely moved from August's $35, so the overall number looks calm.

Split it by channel and the story changes. Paid social went from $40 in August to $50 in September to $60 in October, while search ads came down from $50 to about $38. A flat blended CAC can hide one channel getting worse every month. Build a small grid with months across and channels down, and use the formula below in each cell with the month and channel taken from the headers.

If a month has no new customers for a channel, the division gives #DIV/0!. Wrap it in IFERROR(...,"") so the grid stays readable, and don't read that blank as zero cost.

=SUMIFS(C2:C10,A2:A10,G6,B2:B10,"Paid social")/SUMIFS(D2:D10,A2:A10,G6,B2:B10,"Paid social")

Result: 60

60: October paid social, $1,500 / 25 new customers.

Fully loaded CAC: add the costs that aren't ads

Ad spend is only part of the cost. Email tools, a freelancer who makes your ad creative, a share of a salesperson's time, free samples: if you'd stop paying for it when you stopped looking for customers, it probably belongs in CAC. Put those monthly costs in an input cell (G2) and write down what's in it.

Here $450 a month over 3 months adds $1,350, and CAC rises from $35.03 to $41.88. Whichever version you report, say which one it is and keep it the same every month.

=(SUM(C2:C10)+G2*COUNTA(UNIQUE(A2:A10)))/SUM(D2:D10)

Result: 41.878172589

About 41.88: ($6,900 + 3 months x $450) / 197.

CAC payback months and the CLV:CAC ratio

Payback asks how many months of a customer's gross profit it takes to earn back their CAC. Use monthly revenue per customer (G3) times your margin (G4): $18 x 60% = $10.80 a month. The loaded CAC of $41.88 takes about 3.9 months to recover. Wrap it in ROUNDUP(...,0) if you want whole months: 4.

The other check is CLV / CAC. With a customer lifetime value of $180 in G5, =G5/((SUM(C2:C10)+G2*COUNTA(UNIQUE(A2:A10)))/SUM(D2:D10)) gives about 4.3. Paid social on its own is about 3.6 ($180 / $49.39). The lifetime value guide shows how to get the CLV number from your orders.

=(SUM(C2:C10)+G2*COUNTA(UNIQUE(A2:A10)))/SUM(D2:D10)/(G3*G4)

Result: 3.877608573

About 3.88 months: $41.88 / ($18 x 60%).

Common mistakes

Dividing paid spend by all new customers

That's blended CAC. To judge ads, divide paid spend by customers from paid channels only, and label which one you report.

Counting leads or sign-ups as customers

CAC divides by paying customers. A free trial that never converts isn't a customer yet.

Spend and customers from different periods

Use the same month for both SUMIFS. If people take weeks to buy, compare over a quarter so the timing evens out.

Months stored as text

"Oct 2026" typed as text won't match a real date in G6. Use real first-of-month dates and format them as mmm yyyy.

FAQ

What is the formula for customer acquisition cost?

Total sales and marketing cost for a period / new customers won in that period. In Excel with one row per month and channel: =SUM(spend)/SUM(new_customers), or SUMIFS on both parts for one month or channel.

What costs should be included in CAC?

At least ad spend. A fully loaded CAC also includes marketing tools, agency or freelancer fees and the share of salaries spent on winning customers. Pick a definition, list it next to the number and keep it every month.

What is a good CLV to CAC ratio?

3:1 is a commonly quoted rule of thumb. Under 1:1 you lose money on each new customer. Treat any target as a starting point and check it against your own margins and cash.

How do I calculate CAC payback period?

CAC / (monthly revenue per customer x gross margin). The result is months. Use ROUNDUP(...,0) for whole months.

Functions used

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