The Six Metrics That Matter
1. Customer Acquisition Cost (CAC)
Formula: CAC = Total marketing spend ÷ Number of new customers acquired
What it tells you: How much you pay to get a new customer to make their first purchase. This is the input cost of growth.
Example: You spent $15,000 on ads this month across all channels. You acquired 300 new customers. CAC = $15,000 ÷ 300 = $50.
Benchmarks:
| Channel | Typical CAC |
|---|---|
| Amazon PPC (implied via ACoS) | $8-$25 |
| Google Shopping | $20-$60 |
| Meta Ads (Facebook/Instagram) | $25-$80 |
| TikTok Ads | $15-$50 |
| Email (from existing list) | $1-$5 |
| Organic / SEO | $0-$10 (amortized over time) |
Why Amazon CAC is lowest: Amazon’s built-in traffic and high conversion rate (9-13%) mean fewer ad dollars are needed to generate a purchase compared to driving traffic to a standalone website with 1.5-2.5% conversion.
The mistake to avoid: Calculating CAC based on total revenue divided by total orders. This mixes new customer acquisition with repeat purchases, masking the true cost of growth. Separate new customers from returning customers in your analytics.
2. Customer Lifetime Value (LTV)
Formula (simple): LTV = Average Order Value × Purchase Frequency × Average Customer Lifespan
Formula (contribution-based): LTV = Average Contribution Margin per Order × Number of Orders per Customer over their Lifetime
Example: Average order value: $45. Average customer makes 3.2 purchases over 24 months. LTV = $45 × 3.2 = $144 in revenue, or $144 × 40% margin = $57.60 in contribution.
Benchmarks by business type:
| Business Type | Typical LTV (Revenue) | Typical LTV (Contribution) |
|---|---|---|
| Single-purchase products (electronics, furniture) | 1.0-1.3x first order | $30-$80 |
| Replenishable products (supplements, skincare, pet food) | 3-6x first order | $80-$250 |
| Subscription products | 6-18x monthly value | $150-$500 |
| Fashion / apparel | 1.5-3x first order | $40-$120 |
Why LTV matters more than CAC alone: A brand spending $50 to acquire a customer who spends $144 over their lifetime (at 40% margin = $57.60 contribution) is profitable. A brand spending $30 to acquire a customer who buys once for $35 (at 40% margin = $14 contribution) is losing money.
3. LTV:CAC Ratio
Formula: LTV:CAC = Customer Lifetime Value ÷ Customer Acquisition Cost
What it tells you: For every dollar you spend acquiring a customer, how many dollars of value do you get back?
Benchmarks:
| Ratio | Interpretation | Action |
|---|---|---|
| Under 1:1 | Losing money on every customer | Stop — fix unit economics before scaling |
| 1:1 to 2:1 | Breaking even or marginally profitable | Improve either CAC (better ads) or LTV (better retention) |
| 3:1 | Healthy | The standard target for most e-commerce businesses |
| 5:1+ | Highly efficient | Consider spending more on acquisition — you may be under-investing |
The 3:1 target explained: At 3:1, you earn $3 in value for every $1 spent on acquisition. After accounting for overhead (operations, team, tools, office), you’re left with meaningful profit. Below 3:1, overhead often consumes the remaining margin. Above 5:1, you’re likely under-investing in growth — spending more on acquisition would still be profitable.
4. Contribution Margin per Order
Formula: Contribution Margin = Revenue – COGS – Platform Fees – Shipping – Payment Processing
What it tells you: How much money each order contributes toward covering your fixed costs and generating profit. This is the unit-level profitability metric.
Example (Shopify DTC order):
| Component | Amount |
|---|---|
| Revenue | $45.00 |
| COGS | -$13.50 (30%) |
| Shopify + payment processing | -$3.15 (7%) |
| Shipping | -$5.50 |
| Packaging | -$1.50 |
| Contribution margin | $21.35 (47.4%) |
Example (Amazon FBA order):
| Component | Amount |
|---|---|
| Revenue | $45.00 |
| COGS | -$13.50 (30%) |
| Amazon referral fee (15%) | -$6.75 |
| FBA fulfillment fee | -$4.55 |
| Contribution margin | $20.20 (44.9%) |
Amazon and Shopify produce similar contribution margins in this example — Amazon’s higher fees are offset by not needing to pay for shipping and packaging separately.
The key insight: Contribution margin BEFORE advertising is the maximum you can spend on customer acquisition and still break even on the first order. If your contribution margin is $20 per order, your CAC must stay under $20 to avoid losing money on the first purchase.
5. Payback Period
Formula: Payback Period = CAC ÷ Average Contribution Margin per Month per Customer
What it tells you: How long it takes to recover the cost of acquiring a customer. A 2-month payback means the customer’s purchases in their first 2 months cover the acquisition cost.
Example: CAC = $50. Customer spends $45/month at 45% contribution margin = $20.25/month. Payback = $50 ÷ $20.25 = 2.5 months.
Benchmarks:
| Payback Period | Interpretation |
|---|---|
| Under 3 months | Excellent — fast capital recovery |
| 3-6 months | Good — standard for most e-commerce |
| 6-12 months | Acceptable if LTV is high (subscriptions) |
| Over 12 months | Risky — requires significant capital and confidence in retention |
Why payback matters for cash flow: A 12-month payback period means you invest $50 per customer today and don’t recover that money for a year. If you’re acquiring 500 customers/month, that’s $25,000/month in capital tied up in customer acquisition. Short payback periods let you reinvest faster and grow more aggressively without external capital.
6. Blended ROAS / Marketing Efficiency Ratio (MER)
Formula: MER = Total Revenue ÷ Total Marketing Spend
What it tells you: The overall efficiency of your entire marketing program — not just one channel. MER captures the interaction effects between channels that individual ROAS metrics miss.
Example: Total monthly revenue: $120,000. Amazon ads: $8,000. Google ads: $5,000. Meta ads: $4,000. Email platform: $200. Total marketing: $17,200. MER = $120,000 ÷ $17,200 = 7.0x.
Benchmarks:
| MER | Interpretation |
|---|---|
| Under 3x | Marketing is consuming too much of revenue — optimize or scale down |
| 3-5x | Acceptable for growth-stage brands investing in acquisition |
| 5-8x | Healthy and sustainable |
| 8x+ | Very efficient — consider whether you’re under-investing in growth |
Why MER beats channel-specific ROAS: If your Amazon ROAS is 4x and your Meta ROAS is 2.5x, it looks like Meta is underperforming. But Meta drives brand awareness that increases Amazon search volume — which the Amazon ROAS metric captures as Amazon’s success. MER captures the full picture by measuring all marketing against all revenue.
How to Use Unit Economics for Decisions
Decision 1: Can I Afford to Scale?
Test: Is my LTV:CAC ratio above 3:1? Is my payback period under 6 months? Is my MER above 4x?
If yes to all three: you can scale confidently. Increase ad spend. Enter new channels. Launch new products.
If no: fix the underlying economics before spending more on growth. Scaling a business with broken unit economics just magnifies the losses.
Decision 2: Which Channel Should I Invest More In?
Test: Calculate CAC by channel. Which channel acquires customers at the lowest cost relative to the LTV those customers generate?
| Channel | CAC | Avg LTV from Channel | LTV:CAC |
|---|---|---|---|
| Amazon PPC | $15 | $85 | 5.7:1 |
| Google Shopping | $35 | $130 | 3.7:1 |
| Meta Ads | $55 | $155 | 2.8:1 |
| Email (retention) | $3 | $75 | 25:1 |
In this example, Amazon and email deliver the highest LTV:CAC. Google is healthy. Meta is borderline. The action: scale Amazon and Google first, optimize Meta creative to improve CAC, and invest more in email because it has the highest marginal return.
Decision 3: Should I Raise or Lower My Price?
Test: Model the impact on contribution margin and conversion rate. A 10% price increase that reduces volume by 5% but increases contribution margin by 15% is almost always worth it.
Example: Current price: $40, 500 orders/month, $18 contribution. New price: $44, 475 orders/month, $21.60 contribution. Old total: $9,000. New total: $10,260. Higher profit despite fewer orders.
Decision 4: Is This Product Worth Keeping?
Test: Calculate contribution margin per unit after all variable costs. If it’s negative or under $5 per unit, the product consumes resources without generating meaningful profit. Either raise the price, reduce COGS, or discontinue and redirect resources to higher-margin products.
Building Your Unit Economics Dashboard
Track these metrics monthly in a simple spreadsheet or dashboard:
| Metric | Formula | This Month | Last Month | 3-Month Avg | Target |
|---|---|---|---|---|---|
| CAC (blended) | Marketing ÷ New Customers | Under $40 | |||
| LTV (12-month) | Contribution × Avg Orders in 12mo | Over $120 | |||
| LTV:CAC | LTV ÷ CAC | Over 3:1 | |||
| Contribution Margin % | (Revenue – Variable Costs) ÷ Revenue | Over 40% | |||
| Payback Period | CAC ÷ Monthly Contribution | Under 4 months | |||
| MER | Total Revenue ÷ Total Marketing | Over 5x | |||
| Repeat Purchase Rate | Returning Customers ÷ Total Customers | Over 25% |
Review monthly. Trend matters more than absolute numbers — improving economics month-over-month is more important than hitting benchmarks immediately.
Frequently Asked Questions
What’s the single most important unit economics metric?
Contribution margin per order. It’s the foundation everything else is built on. If contribution margin is negative, no amount of volume, retention, or efficiency improvement can make the business profitable. Fix contribution margin first (through pricing, COGS reduction, or fee optimization), then optimize the other metrics.
How do I calculate LTV when my brand is less than 12 months old?
Use the data you have and project conservatively. If customers who bought 6 months ago have made an average of 1.8 purchases, extrapolate: 12-month LTV ≈ first-6-month value × 1.3-1.5 (accounting for decreasing purchase frequency over time). Update your LTV estimate as you accumulate more data. Avoid overestimating — conservative LTV projections prevent over-investing in acquisition.
My Amazon ROAS is 4x but I’m not profitable. What’s wrong?
ROAS measures ad efficiency, not business profitability. A 4x ROAS means $4 revenue per $1 ad spend. But if your contribution margin (after COGS, referral fees, FBA fees) is only 30%, that $4 in revenue yields $1.20 in contribution — barely covering the $1 ad cost. The fix: either improve contribution margin (lower COGS, higher price) or improve ROAS (better targeting, better listings). See: ACoS vs TACoS →
Should I optimize for revenue or profit?
Profit — always. Revenue without profit is vanity. The exception: during a defined launch phase where you’re intentionally investing in market share (accepting lower or negative profit for 90 days to build ranking and reviews). Even then, set a clear timeline and profitability target for when the investment phase ends.
How do subscription businesses change the unit economics calculation?
Subscriptions dramatically improve LTV because they create predictable, recurring revenue. A customer who subscribes at $30/month for 10 months has $300 LTV — far higher than a one-time purchaser at $30. This allows subscription businesses to accept higher CAC (because the payback is spread over months of recurring revenue). The key metric shifts from first-order profitability to customer retention rate and months-to-churn.
Next Steps
Want your unit economics analyzed? Our free audit includes a profitability assessment for your Amazon and/or Shopify business — contribution margin by product, CAC by channel, and specific recommendations to improve your economics. Get your free audit →
Keep reading:
- Amazon ACoS vs TACoS: Which Metric Matters? →
- Amazon FBA Fees 2026: Complete Cost Breakdown →
- How Much Does It Cost to Sell on Amazon? →
Last Updated: March 2026