Email Marketing Metrics for Ecommerce: The 7 Numbers That Actually Matter

Most email marketing metrics describe the channel. Very few of them describe the business.

Open rate, click rate and platform-attributed revenue can help diagnose an email program, but none of them tell you whether retention is making the business structurally stronger.

The email marketing metrics that actually matter are the ones tied to customer economics: contribution margin after marketing, blended CAC, 30, 60 and 90-day cohort LTV, first-to-second purchase rate, repeat revenue percentage, the flow versus campaign split, and time to second purchase.

For established ecommerce brands, the more useful question is whether customers are becoming more valuable, purchasing again faster and improving the economics of acquisition.

By Emiel Dingemans, Founder of Magicianly

The seven metrics in this guide are:

1. 1Contribution margin after marketing
2. 2Blended CAC
3. 330, 60 and 90-day LTV by cohort
4. 4First-to-second purchase rate
5. 5Repeat revenue percentage
6. 6Flow vs campaign attributed revenue
7. 7Time to second purchase

Only one of those is an email reporting number, and that is intentional.

These are business-level retention metrics. They exist to show whether lifecycle marketing is changing customer economics, not whether a single channel dashboard looks impressive this month.

1. Contribution Margin After Marketing

Revenue growth is not healthy growth if the additional revenue produces worse margins.

Contribution margin looks at what is left from revenue once the variable costs of creating that revenue are removed. Depending on how a brand models it, those costs usually include:

• cost of goods sold;
• shipping and fulfillment where relevant;
• payment processing fees;
• marketing spend.

There is no single universal formula here. Different businesses draw the line between variable and fixed costs differently, so the important thing is to define it once and then measure it consistently over time.

The diagnostic moment comes when revenue rises and contribution margin falls. That combination usually points to one of the following:

• discounting doing more of the selling than the message;
• a product mix shifting toward lower-margin items;
• acquisition getting more expensive;
• weak repeat behavior forcing constant new-customer spend;
• retention tactics that buy orders instead of building value.

2. Blended CAC

Blended CAC judges the acquisition economics of the whole business instead of grading Meta or Google in isolation.

It matters for retention because a stronger lifecycle system increases how much acquisition cost the business can economically tolerate. Customers who buy again, buy sooner and buy more create more value after the first order, which changes what a viable CAC looks like.

Retention does not reduce acquisition spend that has already happened. What it changes is the return the business earns on that spend going forward.

Read blended CAC next to:

• payback period;
• contribution margin;
• cohort LTV;
• subscriber-to-customer conversion;
• repeat purchase behavior.

3. 30, 60 and 90-Day LTV by Cohort

Cohort LTV measures how much value a group of customers acquired in the same period creates within a fixed window after their first order.

Take everyone whose first purchase happened in January. Then look at the revenue or contribution that cohort produced in its first 30 days, first 60 days and first 90 days. Do the same for February, March and every cohort after that.

This is far more useful than one blended lifetime value number, because a blended figure mixes mature customers with customers acquired last week and hides the trend you actually need.

If newer cohorts reach higher 30 and 60-day value than older ones, early retention behavior is likely strengthening. Attribute that carefully: product changes, offer changes, traffic quality and lifecycle marketing all move cohort curves.

4. First-to-Second Purchase Rate

First-to-second purchase rate measures what percentage of first-time buyers place another order.

We pay particular attention to it because it is the clearest single signal that a business is converting acquisition into retention rather than renting revenue from paid media.

A realistic target depends heavily on the business. What shapes it includes:

• product type and whether it is consumed or kept;
• replenishment cycle;
• average order value;
• whether a subscription option exists;
• catalog breadth and cross-sell potential.

For that reason we do not publish a universal target. The number that matters is your own trend by cohort.

It sits directly underneath repeat purchase rate as a measurement, and the work that moves it usually happens in the post-purchase sequence.

5. Repeat Revenue Percentage

Repeat revenue percentage shows what share of total revenue comes from returning customers.

It is useful for understanding how dependent the business is on continuous acquisition. A brand where almost all revenue comes from first-time buyers has to keep spending simply to stand still.

Higher is not automatically better. A brand scaling acquisition quickly can see repeat revenue percentage fall while retention behavior is genuinely healthy, because the new-customer base is growing faster than the repeat base can catch up.

Always read it alongside cohort LTV and repeat purchase rate. On its own it can be misleading in both directions.

6. Flow vs Campaign Attributed Revenue

The split between flow and campaign attributed revenue is a diagnostic, not a goal.

Flows create automated lifecycle revenue triggered by customer behavior. Campaigns create ongoing demand, engagement and reasons to buy now. Both are doing different jobs, so more flow revenue is not automatically a sign of a better program.

There is no ideal split, and a 50/50 target is not a benchmark. Healthy mixes vary with:

• length of the buying cycle;
• whether the product replenishes;
• average order value;
• list size and engagement;
• campaign cadence.

A high-AOV brand with a long consideration cycle can look very different from a consumable brand, as we covered in this high-AOV email and SMS case study.

Note also that these are attributed figures. Attribution shows what a platform credits to a channel. It is not the same as the incremental revenue the channel created.

7. Time to Second Purchase

Time to second purchase measures how long it takes a first-time buyer to order again.

Two brands can share the same second-purchase rate and have very different economics if one gets that order in 30 days and the other in 120.

Speed changes:

• cash velocity;
• early LTV inside the 30 and 60-day windows;
• payback period on acquisition;
• when post-purchase and winback messaging should actually run.

This metric is what should set your lifecycle timing. It determines the shape of the post-purchase flow and the trigger point for the winback flow.

For net audience expansion specifically, use the email list growth rate guide.

Where Open Rate Still Belongs

Open rate is useful. It is simply not a business outcome.

It is a reasonable early indicator of whether your messages are reaching the inbox, whether your audience selection is sensible and whether your subject lines earn attention. That makes it a monitoring number, most valuable when it moves sharply.

It is also a noisy one. Privacy features, prefetching, image blocking and category placement all distort it, so treat a change in open rate as a prompt to investigate rather than as a result.

Apple Mail Privacy Protection and bot clicks are a big reason opens mislead; the practical filters are in our MPP and bot clicks guide.

If open rate is falling across the board, the question is usually a deliverability or list-quality question rather than a copy question. Our email deliverability checklist and list cleaning guide cover that path.

Click Rate Is Diagnostic, Not the Goal

Click rate tells you whether the message created enough interest to move someone to the site. It does not tell you whether that interest turned into profitable revenue.

A campaign can lift click rate and hurt the business by sending traffic to a discount that was not needed, or by attracting clicks from people who were never going to buy at full price.

Read click rate next to:

• placed-order rate;
• revenue per recipient;
• average order value on the resulting orders;
• discount usage;
• unsubscribe and spam complaint rate.

Channel-level numbers like these are still worth tracking properly, and ecommerce email marketing benchmarks are the right place to understand what performance levels tend to look like. This guide is about which metrics to use and how they connect.

Attributed Revenue Is Not Incremental Revenue

This is the single most common measurement problem we see in established email programs.

Attributed revenue is what a platform credits to the channel using its own attribution window. Incremental revenue is the revenue that would not have happened without the message. They are not the same number, and the gap between them can be large.

A discount email sent to people who already had the product in their cart will attribute well and may create very little incremental profit. An abandonment reminder that arrives after someone already decided to buy will do the same.

Practical ways to keep the distinction honest:

• compare attribution against total store revenue and margin over the same period;
• use holdout groups on high-volume flows where the platform supports it;
• watch contribution margin whenever attributed revenue rises;
• be suspicious when a discount-heavy send is the best-performing message of the month.

For how the attribution settings themselves shape the numbers you see, read our guide to Klaviyo attribution.

How We Use These Metrics in an Audit

When we review an account, we start with business metrics and only then look at the email program.

1. 1Establish contribution margin after marketing and blended CAC, so every later decision has a profit constraint.
2. 2Build cohort LTV at 30, 60 and 90 days to see whether customer value is trending up or flat.
3. 3Read first-to-second purchase rate and time to second purchase together to find where the lifecycle actually breaks.
4. 4Check repeat revenue percentage against acquisition growth so the number is interpreted in context.
5. 5Use the flow versus campaign split as a diagnostic of which part of the program is underbuilt.
6. 6Only then open the email reporting, deliverability data and creative.

That order matters, because it changes which fixes get prioritized. The full sequence is written up in our email marketing audit guide.

How These Metrics Work Together

No single metric answers whether retention is working. The useful signal comes from reading them in pairs.

Low first-to-second purchase rate with weak 30-day LTV

The early retention window is the opportunity. Look at post-purchase experience, product guidance and second-order relevance.

Rising CAC with flat cohort LTV

Retention is not offsetting acquisition pressure. Payback is stretching and the business is becoming more fragile even if revenue grows.

Rising attributed email revenue with declining contribution margin

Investigate discounting and incrementality. The channel may be capturing demand it did not create, at a lower margin.

Long time to second purchase with weak early LTV

Examine the post-purchase journey and the timing of every lifecycle message that follows the first order.

For a fuller view of how these numbers connect to acquisition economics, see retention and ecommerce profitability.

The goal is not to make one dashboard number look impressive.

The goal is to build a system in which customer value improves over time.