Build a spreadsheet that calculates acquisition cost, first-year value and payback by channel from your own data.
Farah, a business owner, worked out her acquisition cost, customer value and payback across lessons 8.1 to 8.3. She did the first round on the back of an envelope, the second in a notes app and the third in a spreadsheet tab named "Sheet3". A month later her business partner asked to see the working. She could not find half of it, and the figures she did find no longer matched the latest orders.
The fix is to bring that scattered working into one sheet. The sheet shows acquisition cost, first-year value and payback for each channel, and every input and estimate stays visible. Once it's built, you update it each month by typing in new inputs and nothing else.
Collect the raw numbers for one period before you open a spreadsheet. Last quarter is a good choice. You need six kinds of input, and each one has a source:
Spend comes from ad platform billing pages and invoices. Include ad spend per platform, tools, freelancers and agency fees. New customers come from your source of truth, which is your shop platform, CRM or booking system. Count first-time customers only. Average order value and orders per customer come from your shop or booking records. Gross margin comes from your accounts or supplier invoices. A rough figure is fine if you label it as rough. Tracked customers per channel come from your best attribution view from module 5. This is usually GA4 or your shop platform's own source report. Self-reported customers per channel come from the answers to the source question in lesson 5.3, counted by channel, for the same customers.
The spreadsheet has two tabs, Inputs and Calculations. You type numbers only on Inputs, so the formulas on Calculations never get touched.
On Inputs, give each channel its own row. The columns are channel, ad spend, share of other costs, new customers (tracked), new customers (self-reported), average order value, orders per year and gross margin. The last column is "source and notes". Fill that column in for every row, so anyone reading the sheet can see where each number came from.
Share of other costs is the part of your tools, freelancer fees and an estimate of the owner's time that you give to each channel. You split it between channels in proportion to their ad spend. It is the softest number on the sheet. Shade every estimate cell yellow and add a note explaining how you got the figure.
Farah filled in one quarter for her two channels. Google search had S$1,440 in ad spend (an example figure, as are all of Farah's numbers) and S$480 as its share of other costs. It brought 40 new customers by tracking and 32 by self-report, with an average order of S$100, 2.4 orders per year and a 40 percent gross margin. Meta ads had S$1,800 in ad spend and S$600 as its share of other costs. It brought 60 new customers tracked and 45 self-reported, with an average order of S$75, 2.0 orders per year and a 40 percent gross margin. She shaded the share-of-other-costs cells yellow with the note "estimate, split by ad spend". She shaded gross margin the same way, with the note "owner's estimate from supplier invoices".
Under the channel rows, add one line for the whole business. It holds your total marketing and sales costs for the period and your total new customers. This line includes customers that no ad paid for, such as people who came from email, search results or referrals. For Farah's quarter, the totals were S$5,500 in costs and 160 new customers.
On Calculations, give each channel its own row again. Build every figure with formulas that point at the cells on Inputs, so any change you make there carries through.
Acquisition cost is ad spend plus share of other costs, divided by new customers. For Google, S$1,440 + S$480 = S$1,920, and S$1,920 / 40 = S$48. For Meta, S$1,800 + S$600 = S$2,400, and S$2,400 / 60 = S$40.
First-year value is average order value x orders per year x gross margin. Google comes to S$100 x 2.4 x 40 percent = S$96. Meta comes to S$75 x 2.0 x 40 percent = S$60.
Monthly margin is first-year value divided by 12, which gives S$96 / 12 = S$8 for Google and S$60 / 12 = S$5 for Meta.
Payback, in months, is acquisition cost divided by monthly margin. Google pays back in S$48 / S$8 = 6 months. Meta takes S$40 / S$5 = 8 months.
Put a blended row at the top. It divides whole-business costs by whole-business new customers. For Farah, S$5,500 / 160 is about S$34 per customer. The blended figure comes out lower than any single channel because it counts customers who cost no ad money. This is the anchor figure from lesson 8.1.
Next to the tracked columns, add a second set that works out acquisition cost and payback again using the self-reported customer counts. This self-reported view is the second view of channels from module 5.
For Google, S$1,920 / 32 = S$60 acquisition cost, and S$60 / S$8 = 7.5 months payback. For Meta, S$2,400 / 45 is about S$53, and payback is about 10.7 months.
The tracked and self-reported views will rarely agree. Farah's numbers differ, but both views show Google paying back faster, so she can act on that with more confidence. If your two views disagree sharply, write the disagreement into the sheet where a reader will see it.
The finished sheet has two parts. On the Inputs tab, every number is traced to a source and every estimate is shaded and explained. On the Calculations tab, you can see acquisition cost, first-year value and payback for each channel, with a blended row at the top and the self-reported columns beside the tracked ones. Next month's update means typing the new inputs and nothing else.
When Farah's business partner read the finished sheet, it took five minutes, and they asked one question. It was about the yellow cells, and that is the right question for a reader to ask. If you build your own sheet the same way, your estimates will be the first thing a reader notices.
Build a unit economics sheet showing acquisition cost, first-year value and payback period for at least two channels. Label the inputs and the estimates.
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