There are plenty of statistics floating around about the return on investment (ROI) of email marketing. Some studies even claim businesses can achieve an ROI of up to 4400%.

From my own experience at Bright Cat, there is truth in these glowing reports. Across all the cross-channel campaigns we’ve supported, email marketing usually delivers the strongest ROI.

However, how impressive those figures look depends entirely on how you calculate them and which costs you include.

In this article, we’ll walk through the basic steps for calculating your email ROI, then explore the considerations that help you build a more realistic, reliable picture of your email performance.

What is ROI?

Before diving into email marketing specifically, let’s recap what ROI actually means.

Many small business owners understandably get overwhelmed by marketing jargon — ROI, ROAS, CPA, CPL, LTV… it’s a lot. So let’s keep it simple.

ROI (Return on Investment) is a percentage that shows the return you get compared to the cost you invested:

ROI = (Revenue – Costs) / Costs × 100%

Example:

You spend £1000 on a campaign and generate £7000 in revenue:

ROI = (£7000 – £1000) / £1000 × 100% = 600%

How to Calculate Your Email Marketing ROI

The ROI formula is straightforward. The harder part is determining accurate costs and revenue.

Costs to include

Email marketing involves more than the price of the platform. Consider:

• Email platform subscription

• Cost-per-send fees

• Your time

• Design or copywriting costs

• Email coding or template setup

How to estimate revenue

If you run an e-commerce business, this step is simple — use the revenue attributed to email in your reports.

For service businesses, revenue attribution is trickier. You need to estimate the value of a lead by looking at:

• Average yearly client revenue

• Your lead-to-client conversion rate

Example:

Client pays £1188 per year. You convert 1 in 4 leads.

Lead value = £1188 ÷ 4 = £297 per lead.

Once your costs and revenue are defined, you can run the calculation:

Email ROI = (Revenue – Cost) / Cost × 100%

What About Welcome Emails or Post-Purchase Emails?

Many people wonder whether automated emails should be included in ROI calculations.

There isn’t one “right” way. What matters is consistency.

If you take credit for revenue generated by those emails, include the cost of creating and running them.

For most small businesses, the simplest method is to use:

✔ total email costs
✔ total email revenue

Why Your Email ROI Might Not Be as Strong as You Think

Here’s something many businesses overlook: if you rely only on your email platform’s revenue reporting, you may be double counting sales and inflating your ROI.

A real-world example

Modern customer journeys are messy. A typical buyer might:

1. Click a Facebook ad

2. Leave, then return via a Google search

3. Join your email list

4. Buy after clicking an email

If this customer buys one £99 product:

• Facebook counts the sale

• Google Ads counts the sale

• Your email platform counts the sale

But only one sale actually happened.

This means ROI calculations will look wildly inflated if you rely only on platform data.

Why tracking matters

Using an independent analytics tool, like Google Analytics, helps prevent double counting. Even then, attribution isn’t perfect. Many systems still give credit to the final touchpoint (often email).

Data-driven attribution helps spread credit more fairly, but that is a deeper topic for another day.

For now, the key takeaway is simple:

Be cautious when comparing email ROI to other channels.

Being on your email list usually begins with another marketing touchpoint.

Other Metrics Beyond ROI

ROI is important — but it isn’t the whole story. Other email metrics give clearer, more actionable insight:

Deliverability

• Delivery rate

• Bounce rate

• Spam complaints

These tell you whether your list is healthy.

Engagement

• Open rate
• Click-through rate

These reveal whether your subject lines and content resonate.

Performance testing

A/B test subject lines, CTAs and content variations to improve results over time.

Together, these metrics provide context that ROI alone can’t.

Need Help Understanding Your Email Marketing ROI?

Calculating email ROI looks simple, but as you’ve seen, it takes a bit more thought to reach numbers you can trust.

If you’d like help untangling your email and cross-channel performance, I’d be happy to take a look and highlight opportunities for improvement.

Just get in touch — let’s make your marketing clearer, easier and more effective.