The Question That Changes Your Marketing Strategy
You spend $50K on Facebook ads in March and $50K on Google ads in April. Both drive 1,000 customers.
Which was the better investment?
You can't tell from first-month revenue alone. You need to track these cohorts over time:
March Cohort (Facebook):
- Month 1: $40K revenue (40 customers)
- Month 2: $12K (120 repeat orders)
- Month 3: $8K (80 repeat orders)
- 3-Month LTV: $60K / 1,000 = $60 per customer
April Cohort (Google):
- Month 1: $50K revenue (50 per customer)
- Month 2: $4K (40 repeat orders)
- Month 3: $2K (20 repeat orders)
- 3-Month LTV: $56K / 1,000 = $56 per customer
Facebook looked worse initially but has better repeat behavior. Over 12 months, the gap widens. This is why cohort analysis matters.
Building Cohort Analysis in Excel
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Structure Your Customer Data
Need columns: Customer ID, Order Date, Order Value, First Purchase Date. Export from Shopify: Customers > Export. Use formula =MIN(OrderDate) to find each customer's first purchase date.
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Calculate Months Since First Purchase
Add column: MonthsSince =DATEDIF(FirstPurchaseDate, OrderDate, "M"). Order from cohort's Month 0 = 0, Month 1 = 1, etc. This lets you track behavior over time.
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Build Cohort Pivot Table
Pivot: Rows=Cohort Month, Columns=Months Since, Values=Sum of Order Value. This creates the classic cohort table showing revenue by cohort by month.
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Calculate Cumulative LTV
For each cohort, cumulative LTV = sum across all months. Formula: =SUM(Month0:Month12)/CohortSize. Shows total value generated per customer over 12 months.
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Calculate Repeat Purchase Rate
By cohort by month: =COUNTIFS(Cohort,ThisCohort,MonthsSince,ThisMonth)/CohortSize. Shows % of cohort still buying. Strong cohorts stay above 15% by Month 6.
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Build LTV Projection Model
Use historical repeat rate to project future LTV. If 20% buy in Month 1, 15% in Month 2, project 12-month LTV even for new cohorts with only 3 months data.
The Key Metrics in Cohort Analysis
1. Month-0 AOV (First Purchase Value)
Higher is better, but not the whole story.
Good: $75+
Concerning: Under $30
2. Month-1 Retention Rate
% of customers who buy again in Month 1.
Excellent: 25%+
Good: 15-25%
Average: 8-15%
Poor: <8%
3. Month-6 Cumulative LTV
Total revenue per customer after 6 months.
Calculation: =SUM(M0:M6 revenue) / Cohort Size
Target: 2-3x Month-0 AOV
4. Cohort Half-Life
Months until 50% of repeat revenue is generated.
Fast: 3-4 months (consumables, subscriptions)
Slow: 8-12 months (durable goods, fashion)
5. LTV:CAC Ratio
Lifetime value vs. customer acquisition cost.
Healthy: 3:1 or better
Workable: 2:1
Unsustainable: <2:1
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Common Mistakes to Avoid
Learn from these common pitfalls to ensure success
Comparing cohorts before they have equal time to mature
Solution: Only compare cohorts at the same age. Compare January at Month-6 to February at Month-6, not January at Month-12 to February at Month-1.
Not accounting for seasonal cohort differences
Solution: Q4 cohorts naturally differ from Q2. Compare Q4-2024 to Q4-2023, not Q4-2024 to Q2-2024.
Focusing only on total LTV without looking at repeat rate curves
Solution: A high LTV with 5% Month-1 retention is worse than moderate LTV with 25% retention. The second compounds.
Not segmenting cohorts by acquisition source
Solution: Facebook January and Google January should be separate cohorts. Source matters more than month.
Giving up on cohorts after Month-3
Solution: Some products have 12-18 month repurchase cycles. Track cohorts for at least 18 months to see full picture.
How to Verify Your Numbers
Ensure accuracy with these verification steps
You have at least 6 cohorts with at least 6 months of tracking data
You can identify your best-performing acquisition month and channel
You know your average Month-1 and Month-6 retention rates
You've stopped or reduced spend on channels that drive low-LTV cohorts
You can predict 12-month LTV for new cohorts using historical patterns
Frequently Asked Questions
How many customers do I need in a cohort for it to be meaningful?
Should I track revenue or profit in cohorts?
What if my business is too new for 12-month cohorts?
How often should I review cohort analysis?
Can I use cohort analysis for B2B or high-ticket items?
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