How to Measure Email Marketing ROI (The Right Way)

1. Why email ROI is worth tracking

Email punches far above its cost. Litmus' research puts the average return at roughly $36 for every $1 spent — higher than any other channel — as laid out in their ROI of email marketing report. But that's an average, and averages hide a wide range. The only way to know your return — and to defend or grow your email budget — is to measure it.

2. The ROI formula

ROI itself is simple:

ROI = (revenue from email − cost of email) ÷ cost of email × 100

If you spend $200 a month on your email tool and time, and email drives $1,400 in sales, your ROI is ($1,400 − $200) ÷ $200 × 100 = 600% — $6 back for every $1 in. The hard part isn't the math; it's getting honest numbers for the two inputs, especially the revenue side.

3. The metrics behind the money

ROI is the destination, but these are the levers that move it. Mailchimp's guide to measuring email success walks through them:

• Open rate — did the subject line earn attention?
• Click rate (CTR) — did the content earn action? This is the strongest engagement signal.
• Conversion rate — of those who clicked, how many bought or signed up? This is where revenue actually happens.
• Revenue per email / per subscriber — the figure that ties effort to money.
• Unsubscribe & list growth — the long-term health of the asset you're monetising.

A high open rate with low conversions tells a different story than the reverse — track the chain, not just the top.

4. Connecting emails to revenue

The trickiest part of email ROI is attribution — knowing which sale came from which email. A few practical ways to close the gap:

• Use unique links or codes per campaign so purchases trace back.
• Tag your links with UTMs so email traffic and conversions show up clearly in your analytics.
• Watch the window. People often click today and buy in a few days — don't only count same-session sales.

5. How to improve your email ROI

Because email's costs are low and fixed, ROI improves mostly by lifting the revenue side:

• Grow and clean your list. More engaged subscribers (and fewer dead ones) raise returns and protect deliverability.
• Segment. Relevant emails to the right people convert far better than blasts to everyone.
• Improve the click, not just the open. A compelling offer and one clear CTA drive the conversions that make money.
• Automate the high-ROI flows — welcome and abandoned-cart sequences often out-earn one-off campaigns.

Start by plugging your numbers into the formula so you have a baseline — then you can see whether each change actually moves the return.

To judge your inputs, compare them against email open & click benchmarks, and remember to tag your links with UTMs so the revenue actually traces back to email.