How to Track Email Marketing ROI

Email marketing ROI is calculated by dividing the revenue generated by email minus your email marketing costs by those costs, then multiplying by 100. The industry average is $36 to $42 return for every dollar spent, but this number is meaningless unless you track it accurately with proper attribution. Setting up correct revenue tracking lets you justify email marketing spend, identify underperforming areas, and allocate budget to the highest-return channels.

The ROI Formula for Email Marketing

The basic formula is straightforward: (Email Revenue - Email Costs) / Email Costs x 100 = ROI Percentage. If your email marketing generated $15,000 in revenue last month and your total costs (platform, tools, labor) were $500, your ROI is ($15,000 - $500) / $500 x 100 = 2,900%. That means for every dollar you spent on email, you got $29 back in revenue.

The complexity is not in the formula but in accurately measuring each component. Email revenue depends on your attribution model, which determines which sales count as email-driven. Email costs include platform subscription, SMS fees if applicable, design tools, and any time spent creating and managing campaigns.

Understanding Attribution Models

Attribution determines which purchases get credited to email versus other channels. Most email platforms use last-touch attribution with a time window: if a subscriber opened or clicked an email within X days before making a purchase, that purchase is attributed to email. The typical default window is 5 days for Klaviyo and 7 days for Mailchimp.

Open-based attribution credits a purchase to email if the subscriber opened the email within the attribution window before buying. This casts the widest net and generates the highest reported email revenue, but it may over-attribute because someone might have opened the email but purchased because of a separate Google search or social media ad.

Click-based attribution credits a purchase to email only if the subscriber clicked a link in the email before buying. This is more conservative and represents purchases where the email directly drove the visitor to the store. Click-based attribution typically shows 30% to 50% less revenue than open-based attribution for the same campaigns.

Which to use: Track both but make decisions based on click-based attribution because it represents more directly email-driven purchases. Use open-based attribution as a ceiling estimate. If you report email performance to stakeholders, clarify which attribution model you are using so everyone understands the numbers consistently.

One important caveat: email attribution in your email platform and revenue attribution in Google Analytics will not match. Google Analytics uses its own attribution model, typically last-click with a 30-day window, and attributes many email-driven purchases to "direct" or "organic search" if the subscriber typed your URL directly or searched your brand name after reading the email. This is why email platform attribution, despite its imperfections, is a better measure of email's true impact than Google Analytics alone.

Key Metrics to Track Monthly

Revenue Metrics

Total email revenue: The sum of all revenue attributed to email campaigns and automated flows. This is your headline number. Healthy ecommerce stores see email contributing 20% to 40% of total revenue.

Revenue per subscriber: Total email revenue divided by total active subscribers. This tells you how valuable each subscriber is on a monthly basis. Top-performing stores generate $1 to $3 per subscriber per month. If your number is significantly lower, you have optimization opportunities in your flows and campaigns.

Revenue per email sent: Total email revenue divided by total emails sent. This metric helps you understand the efficiency of each send and compare campaign types. Automated flows typically show 5x to 10x higher revenue per email than broadcast campaigns because they are triggered by high-intent behavior.

Flow revenue vs. campaign revenue: Break down total email revenue into automated flow revenue and manual campaign revenue. Top-performing stores see 60% to 70% from flows and 30% to 40% from campaigns. If your flow percentage is low, you have missing or underperforming automations. If your campaign percentage is low, you may not be sending enough campaigns or your campaign content needs improvement.

Engagement Metrics

Open rate: Percentage of delivered emails that were opened. Industry average is 18% to 25% for ecommerce. Track trends over time rather than fixating on individual campaign numbers, and be aware that Apple Mail Privacy Protection inflates open rates for Apple users.

Click-through rate: Percentage of delivered emails where a link was clicked. Average is 2% to 5%. This is a more reliable engagement metric than open rate because clicks represent active interest.

Conversion rate: Percentage of email recipients who made a purchase. Average is 1% to 3% for campaigns, higher for behavioral flows like abandoned cart and browse abandonment.

List Health Metrics

List growth rate: Net new subscribers per month minus unsubscribes and bounces. Healthy growth is 3% to 5% of list size per month. If growth stalls, review your list building tactics and signup form performance.

Unsubscribe rate: Should stay under 0.3% per campaign send. Above 0.5% indicates content relevance or frequency problems. Track per-campaign to identify which email types drive the most unsubscribes.

Spam complaint rate: Must stay under 0.1% per send. Above 0.3% risks deliverability damage. If complaints spike, review recent sends for content quality, frequency, and whether your list includes non-opted-in contacts.

Building Your Monthly Report

Create a simple dashboard or spreadsheet that tracks these metrics monthly. Include total email revenue, email as a percentage of total store revenue, revenue per subscriber, top-performing flow by revenue, top-performing campaign by revenue, list size and growth rate, average open rate, average click-through rate, and total email costs. Comparing month over month reveals trends that individual campaign analytics cannot show.

Add qualitative notes to your monthly report: what you tested, what you launched, and what external factors (seasonal trends, promotions, product launches) influenced results. These notes give context to the numbers and help you distinguish between real performance changes and seasonal or circumstantial fluctuations.

Benchmarking Against Your Industry

Email marketing benchmarks vary significantly by industry. Fashion and apparel stores typically see 15% to 20% open rates, 2% to 3% click rates, and email contributing 25% to 35% of revenue. Health and beauty stores see higher engagement with 20% to 25% open rates. Electronics and technology stores see lower engagement at 12% to 18% but higher average order values from email-driven purchases.

Use industry benchmarks as directional guidance, not absolute targets. Your specific performance depends on list quality, sending frequency, content quality, and how well your automation flows are optimized. A store with a small, highly engaged list will outperform benchmarks. A store with a large, partially disengaged list will underperform. Focus on improving your own metrics month over month rather than chasing industry averages.

The ultimate benchmark is ROI compared to your other marketing channels. If email generates $30 per dollar spent while Google Ads generates $4 and social media generates $2, email deserves proportionally more of your time and investment. Track ROI across all channels quarterly to ensure you are allocating resources to the highest-returning opportunities.