How the LTV:CAC & Payback Period Calculator Works
One of the costliest mistakes in e-commerce finance is computing Customer Lifetime Value (LTV) using gross top-line revenue rather than Contribution Margin. If a customer spends $200 over a year at a 50% variable margin, your business only retains $100 to pay back acquisition ads—meaning a $70 CAC yields a 1.43:1 true LTV:CAC ratio, not 2.85:1.
Equally critical is Velocity of Payback (CAC Payback Window). A 4.0:1 LTV:CAC ratio that takes 14 months to break even can still bankrupt a bootstrapped brand if inventory reorder cycles demand cash every 60 days.
This simulator models monthly repeat purchase propensity alongside natural cohort retention decay over 12 months, giving founders an honest view of both cash payback speed and cumulative net profit per acquired buyer.
Contribution LTV & Cohort Payback Equations
1. Day-1 Net Cash Position
Day-1 Net = (First-Order AOV × Contribution Margin %) - Paid CAC
Positive Day-1 Net means every new customer self-finances growth immediately without burning working capital.
2. Decaying Monthly Cohort Orders
Month(m) Orders = Monthly Repeat Rate % × (1 - Decay %)^(m - 1)
Reflects real-world retention curves where repeat purchase probability gradually tapers over time.
3. True 12-Month Contribution LTV
12M Margin LTV = Day-1 Margin + Sum(Month 1..12 Repeat Margin - CRM Costs)
Strips out COGS, shipping, payment fees, and retention email/SMS costs from lifetime revenue.
4. Contribution LTV : CAC Ratio
LTV : CAC = 12-Month Contribution LTV / Paid CAC
Healthy bootstrapped DTC brands target >= 3.0:1 over 12 months with CAC payback under 60–90 days.
12-Month LTV:CAC & Payback Benchmarks by Store Model
Use these reference ranges across e-commerce verticals to sanity-check your store's inputs when modeling scenarios:
| E-Commerce Business Model | Healthy 12M LTV:CAC | Target CAC Payback | Typical 12M Order Frequency |
|---|---|---|---|
| Consumables & Supplements (Subscription) | 3.2:1 – 5.0:1 | 30 – 90 Days | 3.2x – 5.5x orders/yr |
| Skincare, Haircare & Coffee | 2.8:1 – 4.2:1 | Day 1 – 60 Days | 2.1x – 3.4x orders/yr |
| Apparel & Lifestyle Brands | 2.2:1 – 3.2:1 | Day 1 (First Order) | 1.4x – 2.0x orders/yr |
| Single-SKU Durable Goods / Furniture | 1.8:1 – 2.5:1 | Day 1 Mandatory | 1.05x – 1.25x orders/yr |
Common Questions About LTV:CAC & Payback Period Calculator
Why does UnitProfitLab calculate LTV on Contribution Margin instead of Gross Revenue?
Because COGS, parcel shipping, and payment gateway fees recur on every repeat order. Only the net variable contribution margin left over can actually pay back Customer Acquisition Cost (CAC) and fund company overhead.
What is a healthy LTV:CAC ratio for a bootstrapped e-commerce store?
On a 12-month Contribution Margin basis (not gross revenue!), 2.5:1 to 3.5:1+ is strong—provided your CAC Payback Window is Day 1 or under 60 days so ad scaling does not starve inventory cash flow.
When is it safe to lose money on the first order?
Only when you have at least 6 months of verified historical cohort data proving predictable 30-to-60-day replenishment (such as subscriptions) and dedicated working capital to fund the payback trough.
How can I shorten my CAC Payback Period without cutting ad spend?
Add a post-purchase one-click upsell immediately after checkout to boost Day-1 AOV by 15%–25%, and trigger a replenishment email/SMS sequence timed specifically to your product's 25-to-40-day depletion cycle.