Six metrics determine whether an e-commerce business is growing sustainably or spinning its wheels. Most operators know their revenue; far fewer know their CAC by channel, their true CLV, or whether their churn rate is quietly undermining every acquisition they fund. This guide covers each metric — what it is, how to calculate it, what the benchmarks are, and what to do when the number is wrong.
Overview
E-commerce measurement can be divided into two groups: acquisition metrics that tell you whether you are bringing in customers efficiently, and retention metrics that tell you whether those customers are worth what you paid to acquire them. A business can fail by optimising either group in isolation.
- Acquisition: CAC, ROAS, Conversion Rate, Cart Abandonment
- Retention: CLV, Churn Rate, Repeat Purchase Rate, AOV
The six steps below cover these in the order that creates actionable clarity — starting with the revenue foundation, then acquisition efficiency, then retention and lifetime economics.
Step 1: Track Revenue and Gross Margin
GMV (Gross Merchandise Value) and revenue are not the same number, and confusing them is one of the most common mistakes in e-commerce analysis.
GMV vs Revenue
GMV is the total value of goods ordered — the full selling price multiplied by units sold, before any deductions. Revenue is what your business actually recognises: GMV minus returns, refunds, and in marketplace contexts, minus the seller's portion of the sale price. For a direct-to-consumer brand, GMV and revenue are close; for a marketplace, GMV can be 10–20x revenue.
Average Order Value (AOV)
AOV = Total Revenue ÷ Number of Orders
Track AOV monthly and by traffic source. A declining AOV usually indicates customers are buying cheaper items (product mix shift), promotions are training customers to buy less per trip, or the discount strategy is eroding basket size. An increasing AOV suggests bundling, upsell mechanics, or natural category migration is working.
Gross Margin
Gross Margin % = (Revenue − COGS) ÷ Revenue × 100
COGS includes product cost, packaging, and inbound freight. It does not include outbound shipping, returns processing, marketing, or technology. Gross margin is the ceiling that all operating expenses must fit beneath. Common benchmarks:
- Fashion/apparel: 55–70%
- Beauty/personal care: 50–65%
- Electronics: 15–30%
- Consumables/FMCG: 30–45%
Never run a CAC analysis without knowing your gross margin percentage first. A $30 CAC on a product with 25% gross margin and $80 AOV ($20 gross profit per order) is a money-losing situation, regardless of how good the ROAS looks.
Step 2: Calculate Customer Acquisition Cost (CAC)
CAC is the total spend required to acquire one paying customer. It is the most important input for evaluating whether your paid marketing channels are financially viable.
The formula
CAC = Total Acquisition Spend ÷ Number of New Customers Acquired
Define "acquisition spend" carefully: include ad spend, agency fees, content production costs attributable to acquisition campaigns, and any promotions or discounts offered to first-time buyers. Define "new customers" as first-time buyers only — do not dilute CAC by including repeat purchases in the denominator.
Calculate CAC by channel
Overall CAC masks channel-specific economics that are often wildly different:
| Channel | Typical CAC range | Notes |
|---|---|---|
| Google Search | $20–$60 | High intent; strong for transactional categories |
| Google Shopping | $15–$45 | Effective for comparison shoppers |
| Meta (Facebook/Instagram) | $25–$80 | Strong for visual categories; CPMs rising |
| TikTok | $15–$50 | Younger demographics; creative-dependent |
| Email (to own list) | $2–$8 | Acquisition from an existing audience asset |
| Influencer | $30–$150 | Wide variance; attribution is difficult |
If Meta CAC is $55 and Google Search CAC is $22, the decision is to scale Google and audit Meta creative before increasing Meta budget. Use the CAC Calculator to calculate channel-specific CAC from your actual spend and acquisition data.
Blended vs channel CAC
Blended CAC (all spend ÷ all new customers) is useful as a single headline number but misleading for budget allocation. A blended CAC of $30 might include a $15 CAC on email list acquisition and an $80 CAC on TikTok awareness campaigns — very different economics that require very different decisions.
Step 3: Measure Customer Lifetime Value (CLV)
CLV answers the question: how much revenue (and more importantly, profit) will a customer generate over their relationship with your brand? This is the number to compare CAC against.
The formula
CLV = AOV × Purchase Frequency per Year × Customer Lifespan in Years
For profit-based CLV: Profit CLV = CLV × Gross Margin %
Example: AOV = $75, purchase frequency = 3×/year, average customer lifespan = 3.5 years, gross margin = 50%. CLV = $75 × 3 × 3.5 = $787.50 Profit CLV = $787.50 × 50% = $393.75
If CAC is $40, the profit CLV:CAC ratio is approximately 9.8:1 — an excellent position.
The CLV:CAC ratio
| Ratio | Interpretation |
|---|---|
| < 1:1 | Losing money on every customer; unsustainable |
| 1:1 to 2:1 | Marginally profitable; limited growth capacity |
| 3:1 | Healthy; sufficient margin to fund growth |
| > 5:1 | Potentially under-investing in acquisition |
A ratio above 5:1 is not necessarily a sign of health — it may indicate you are being too conservative with acquisition spend and leaving growth on the table. A 3:1 ratio is the target in most well-run e-commerce businesses.
Use the CLV Calculator to model CLV under different retention assumptions. The single largest lever on CLV is purchase frequency — increasing average purchases from 2× to 3× per year improves CLV by 50% with no change in AOV or lifespan.
Step 4: Analyse ROAS by Channel
ROAS (Return on Ad Spend) measures revenue generated per dollar of advertising cost. It is the metric most commonly reported by ad platforms and the most commonly misunderstood.
The formula
ROAS = Revenue Attributed to Ads ÷ Ad Spend
A ROAS of 4.0 means $4 in revenue for every $1 spent. Ad platforms calculate ROAS automatically, but their attribution windows vary — Google's default is a 30-day click, Meta's default is a 7-day click / 1-day view. This means the same purchase may be attributed to multiple channels, inflating reported ROAS across platforms simultaneously.
Breakeven ROAS
Breakeven ROAS = 1 ÷ Gross Margin %
At 40% gross margin: breakeven ROAS = 1 ÷ 0.40 = 2.5. Below a ROAS of 2.5, you are spending more than you earn in gross profit.
At 25% gross margin: breakeven ROAS = 4.0. This is why electronics brands need very different ROAS targets than beauty brands.
Target ROAS by category
| Category | Gross margin | Breakeven ROAS | Target ROAS |
|---|---|---|---|
| Fashion/apparel | 55% | 1.8 | 3.5–5.0 |
| Beauty | 60% | 1.7 | 4.0–6.0 |
| Electronics | 20% | 5.0 | 7.0–10.0 |
| Consumables | 40% | 2.5 | 4.0–5.5 |
Target ROAS should exceed breakeven ROAS by enough to cover shipping, fulfilment, technology, and overhead costs — which typically consume an additional 15–30% of revenue. Use the ROAS Calculator to determine your specific breakeven ROAS and set channel-level targets accordingly.
The ROAS vs profitability tension
A high ROAS on a small budget is not the same as a profitable marketing programme. You can achieve a 10:1 ROAS on a $1,000 spend while spending $200,000 unprofitably on the same channel. Scale matters. The correct optimisation is to increase spend on a channel until marginal ROAS drops to the breakeven threshold — not to maintain a high average ROAS by keeping budgets small.
Step 5: Monitor Conversion Rate and Cart Abandonment
Conversion rate and cart abandonment rate are the metrics that most directly reflect the quality of the shopping experience — from traffic arrival to completed purchase.
Conversion rate
Conversion Rate = Orders ÷ Sessions × 100
The global e-commerce average is 1–3%, but this varies dramatically by channel:
- Direct / return visitors: 4–6%
- Email campaign traffic: 3–5%
- Google Search (high intent): 2–4%
- Google Shopping: 1.5–3%
- Meta paid social: 0.5–1.5%
- Organic social: 0.2–0.8%
- Display/awareness: 0.1–0.3%
A conversion rate below 1% on paid search — which captures buyers actively looking for your product category — indicates a product-page, pricing, or trust problem, not a targeting problem. Increasing spend against a broken conversion funnel amplifies losses, not revenue.
Cart abandonment rate
Cart Abandonment Rate = (1 − Orders ÷ Cart Initiations) × 100
The global benchmark is 68–72%. This means 7 in 10 shoppers who added to cart did not buy. The drivers are:
- Unexpected shipping cost (seen only at checkout): ~48% of abandonment
- Forced account creation: ~24%
- Complicated checkout process: ~18%
- Payment security concerns: ~17%
- Delivery timeline too slow: ~16%
Tactical interventions with high ROI:
- Show shipping cost — or a "free shipping above $X" callout — on the product page, not just at checkout. This eliminates the biggest surprise.
- Guest checkout: a forced registration step costs more in abandonment than it saves in email capture.
- Cart abandonment email sequences: a three-email sequence (1 hour, 24 hours, 72 hours after abandonment) can recover 5–10% of abandoned carts. At 70% abandonment rate on 10,000 monthly cart initiations, recovering 7% of abandoned carts at average $75 AOV = $36,750 in additional monthly revenue.
Use the Conversion Rate Calculator to track conversion across campaigns, devices, and product categories, and to identify where in the funnel the largest drop-offs occur.
Step 6: Track Churn and Repeat Purchase Rate
For subscription businesses and high-frequency purchase categories, churn and repeat purchase rate are the metrics that determine long-term viability. An e-commerce business with excellent acquisition metrics but poor retention is a bucket with a hole in it.
Churn rate
Monthly Churn Rate = Customers Lost in Month ÷ Customers at Start of Month × 100
For subscription e-commerce (boxes, meal kits, replenishment subscriptions), monthly churn is the primary retention metric. The compounding effect is severe:
| Monthly churn | Customers retained after 12 months |
|---|---|
| 1% | 89% |
| 2% | 79% |
| 3% | 70% |
| 5% | 54% |
| 8% | 37% |
At 5% monthly churn, you lose 46% of your subscriber base every year. With a CAC of $45 per subscriber, replacing that lost base costs 46% × total subscribers × $45 every year — a substantial headwind to growth. Use the Churn Rate Calculator to model the annual subscriber count under different churn scenarios and calculate the acquisition budget required to achieve net growth targets.
Repeat purchase rate
Repeat Purchase Rate = Customers With ≥ 2 Purchases ÷ Total Customers × 100
This metric applies to all e-commerce, not just subscriptions. A repeat purchase rate of 25–35% within the first 12 months is typical for fashion and home goods; 40–60% for consumables, beauty, and pet products.
Increasing repeat purchase rate is typically achieved through:
- Post-purchase email sequences that build product familiarity and prompt a second purchase
- Replenishment reminders timed to when the product should be running out
- A loyalty programme that creates an accumulation incentive
- Product discovery campaigns to existing customers showing related products they have not yet bought
The difference in business economics between a 25% and a 40% repeat rate is significant. At 25% repeat, most revenue requires continuous acquisition spend. At 40%, a growing share of revenue is generated from existing customers at near-zero marginal cost.
Key Terms
- CAC — Customer Acquisition Cost; total spend to acquire one paying customer, calculated by channel for actionable insight
- CLV — Customer Lifetime Value; total revenue (or profit) generated by one customer over their entire relationship with the brand
- ROAS — Return on Ad Spend; revenue attributed to advertising divided by advertising cost; breakeven ROAS = 1 ÷ gross margin
- Conversion Rate — percentage of website sessions that result in a completed order; varies by traffic source from 0.2% (display) to 5%+ (email to engaged list)
- Cart Abandonment Rate — percentage of shoppers who initiate a cart but do not complete purchase; global average 68–72%
- Churn Rate — rate at which customers stop purchasing; for subscriptions, typically measured monthly; a 5% monthly churn equals 46% annual customer loss
- GMV — Gross Merchandise Value; total value of goods ordered before deductions for returns, refunds, and commissions
- AOV — Average Order Value; total revenue divided by number of orders; a primary lever for improving unit economics without increasing acquisition spend