Which metrics matter for B2C e‑commerce at CMO level (not just performance reports)

There's a specific kind of blindness that happens in e-commerce marketing. The team produces weekly reports full of numbers — CTR, CPC, ROAS, impressions, sessions, add-to-cart rate — and everyone feels informed. But nobody in the room can answer the question that actually matters: "Is our marketing building a profitable, sustainable business?"

Channel-level dashboards are operational tools. They help media buyers optimise campaigns. But they don't tell a CMO whether the business is healthy. For that, you need a different set of metrics — ones that connect marketing activity to commercial outcomes.

The typical anti-pattern

Here's what I see in most e-commerce companies: the marketing team presents a weekly deck with 15 slides of channel performance data. ROAS looks great on paid social. Google Shopping CPC went down. Email open rates are up.

Meanwhile, gross margin is eroding because the best-performing campaigns are all pushing discounted products. Return rates on the fastest-growing category are 35%. And repeat purchase rate has been declining for three quarters, but nobody's tracking it because it's "not a marketing metric."

This is the anti-pattern: measuring what's easy to measure instead of what actually drives the P&L.

Metric 1: Revenue (and revenue composition)

What it is: Total revenue, broken down by new vs. returning customers, by category, by channel, and by full-price vs. discounted.

Why it matters at CMO level: Raw revenue is table stakes. What a CMO needs to see is the composition. Are you growing because new customers are converting, or because existing customers are buying more? Is growth coming from your core category or a discount-driven flash sale? Revenue composition tells you whether growth is structural or temporary.

How it connects marketing, merch and ops: If revenue growth is driven entirely by new customer acquisition through paid channels, you're renting your growth. Marketing needs to work with merchandising on assortment strategy and with CRM on retention programmes to shift the mix toward organic and repeat revenue.

Decision trigger: If new customer revenue exceeds 70% of total and repeat revenue is flat, reallocate at least 20% of acquisition budget to retention and reactivation campaigns. The maths almost always favour it.

Metric 2: Gross Margin

What it is: Revenue minus cost of goods sold (COGS), expressed as a percentage. In e-commerce, COGS includes product cost, shipping, packaging, and payment processing.

Why it matters: Gross margin is the first reality check. You can have brilliant ROAS numbers while destroying margin by promoting low-margin products or eating shipping costs. A CMO who doesn't watch gross margin is flying blind.

The marketing connection: Promotion strategy, product mix in ads, free shipping thresholds — these are marketing decisions that directly affect gross margin. If your highest-performing campaign drives traffic to your lowest-margin products, you're optimising for the wrong thing.

Decision trigger: If gross margin drops below your target for two consecutive months, audit the top 10 campaigns by spend and check which products they're actually driving. Often, a small adjustment — shifting ad spend from a 25% margin product to a 55% margin product — fixes the problem without reducing volume.

Metric 3: CAC (Customer Acquisition Cost)

What it is: Total marketing spend on acquisition divided by the number of new customers acquired. In e-commerce, this should be calculated on a blended basis (all channels) and per-channel.

Why it matters: CAC tells you the price of growth. In e-commerce, CAC is rising across most channels because competition for attention keeps increasing. A CMO needs to know the real, all-in CAC — not the CPA from a single campaign.

How to calculate it honestly: Include all marketing spend (paid, organic team costs, influencer fees, agency costs), not just ad spend. Divide by genuinely new customers, not repeat purchasers who came through a paid ad. Most e-commerce companies undercount their real CAC by 30–50%.

Decision trigger: If blended CAC exceeds the gross profit on the first order, you're betting on repeat purchases to break even. That's fine — if you can prove repeat rates are high enough. If not, you're subsidising growth with margin.

Metric 4: Customer Lifetime Value (LTV)

What it is: The total gross profit a customer generates over their entire relationship with the brand. In e-commerce, this is typically calculated over 12 or 24 months because customer relationships are more transactional than in SaaS.

Why it matters: LTV turns a transaction business into a relationship business — at least in theory. A high LTV justifies a higher CAC. But most e-commerce companies calculate LTV using revenue, not gross profit, which dramatically overstates the real number.

Practical note: Calculate LTV by cohort and by acquisition channel. Customers acquired through heavy discounting often have 40–60% lower LTV than customers who bought at full price. This single insight can reshape your entire acquisition strategy.

Decision trigger: If LTV-to-CAC ratio is below 3:1, you need to either increase repeat purchase rates, increase average order value, or reduce CAC. The fastest lever is usually improving the post-purchase experience — a great unboxing, a well-timed reorder reminder, personalised recommendations.

Metric 5: Repeat Purchase Rate

What it is: The percentage of customers who make a second purchase within a defined timeframe (typically 90 or 180 days).

Why it matters: This is the metric that separates real e-commerce businesses from expensive customer-acquisition machines. A repeat rate above 30% within 90 days is strong. Below 15% means your product or experience isn't sticky enough to build a sustainable business.

Why CMOs should care: Repeat purchase rate is the ultimate verdict on whether your brand, product and experience actually work together. High repeat rates mean customers trust you. Low repeat rates mean something is broken — and no amount of ad spend will fix it.

Decision trigger: If repeat purchase rate drops below 20%, invest in post-purchase experience before spending another dollar on acquisition. Look at: order delivery experience, product quality consistency, email/SMS reactivation timing, and loyalty programme structure.

Metric 6: Return Rate

What it is: The percentage of orders returned, by category and by channel.

Why it matters: Returns are the hidden profit killer in e-commerce. A product with 30% return rate needs to sell 43% more units just to deliver the same net revenue as a product with 5% returns. And returns carry real costs: processing, restocking, customer service time, and write-offs.

The marketing connection: Return rates often correlate with acquisition channel. Impulse purchases from social media ads tend to have higher return rates than purchases from organic search. If your paid social campaigns show great ROAS but 25% returns, the real ROAS is much lower.

Decision trigger: If any category exceeds 20% return rate, work with merchandising on product descriptions, sizing guides, and photography accuracy. If returns correlate with a specific acquisition channel, adjust targeting or creative to set better expectations.

A weekly CMO view for e-commerce

Everything above should fit on one page. Here's what I'd want to see every Monday morning:

Top line: Revenue this week vs. plan vs. same week last year. Split: new customer revenue / returning customer revenue / full-price revenue / discounted revenue.

Unit economics: Blended CAC, gross margin %, return rate by top 3 categories.

Health indicators: Repeat purchase rate (rolling 90-day), LTV:CAC ratio (rolling quarterly), active customer count trend.

Operational flags: Any category with return rate above 20%. Any channel with CAC above first-order gross profit. Any week where discounted revenue exceeds 40% of total.

One page. No slides. No commentary needed if the numbers are clear.

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*This article is part of the [Metrics Hub](/metrics) — a practical library of metrics for founders, CMOs and growth leaders. See also: [5 essential metrics for B2B SaaS](/article/5-essential-metrics-b2b-saas-growth) and [Metrics for B2B2C](/article/metrics-b2b2c-partners-end-users).*