Analytics is the core part of email marketing. Every email marketer must monitor key performance indicators, or KPIs, to evaluate their campaign’s success and know how to adjust their strategy. But what are these email marketing KPIs, and what should you know about them? This article answers the question. Read on as we dive into marketing KPIs, their importance, and how to measure them.
What are KPIs in email marketing?
KPIs stands for key performance indicators, and the term is pretty self-explanatory. KPIs are quantifiable measures of performance for a specific task. For email marketing, they provide targets to aim at and milestones for those targets. In summary, KPIs measure the success of your email marketing campaign.
Email KPIs are not synonymous to email metrics, although people often use these terms interchangeably. Metrics include a wider range of data points related to an email campaign, such as the number of emails sent and opened, the number of link clicks, etc. KPIs are a subset of these metrics relevant to an email marketer's current objectives. KPIs measure specific goals, while metrics evaluate mailing campaigns in general. For example, if you aim to increase the number of people reading your emails, email open rate becomes your target KPI.
How to calculate email marketing KPIs
Most email KPIs have simple formulas to calculate them. For example, the open rate is the number of people who opened an email divided by the total emails delivered, expressed as a percentage. The deliverability rate is the number of emails delivered to recipients’ mailboxes divided by the total number of emails you’ve sent, expressed as a percentage.
However, it’s inconvenient to calculate these KPIs manually, and you’ll eventually make mistakes if you do that. That’s why analytics is a core consideration when choosing an email service provider (ESP) to deliver your marketing and transactional messages.
Any worthwhile ESP should offer accurate analytics to users, preferably in real time. You should have access to an interactive dashboard to monitor your KPIs and be able to observe their changes over time. Luckily, you have that in UniOne, a first-rate email service provider with extensive analytics tools. With this platform, you’ll have no issues monitoring your KPIs and knowing when to make crucial changes to improve them.
11 email marketing KPIs to pay attention to
Deliverability rate
Deliverability rate is the percentage of your emails that get to the intended recipients. You may have 1,000 addresses on your mailing list, but that doesn’t necessarily mean your email would reach 1,000 people. Some emails might get flagged as spam (false positives included); some addresses might be invalid and unable to receive emails; an email provider might have technical issues processing your email at a specific moment. Regardless, 100% deliverability is almost never possible.
Deliverability is calculated by dividing the number of delivered emails by the total number of emails sent. Then, multiply the result by 100 to express it as a percentage. For example, if you sent 1,000 emails, of which 900 were delivered, your deliverability rate is 900/100 =90, or 0.90x100= 90%. A good email delivery rate hovers between 90% and 98%. Anything below 90% indicates a problem that should be rectified.

You can take several steps to improve your deliverability rate, such as sanitizing your mailing lists, using a dedicated IP address, setting up email authentication, and choosing a reliable email service provider (ESP) which provides robust infrastructure to deliver your emails to the intended recipients.
Open rate
It’s one thing to deliver an email and another for the recipient to open it. The open rate is the percentage of recipients who opened an email out of the total number of delivered emails. In the above example, if 900 people received your messages and 180 of them opened them, the open rate is 180/900 = 0.20 or 0.20x100 = 20%.

You can get high open rates by using creative subject lines and sending relevant content. Personalization, i.e., sending subscribers targeted emails based on the data you have about them, helps your open rate greatly. A common example is sending an email starting with “Hi, [Subscriber’s First Name]”. Including a subscriber’s name in the email’s subject makes them more likely to open it.
The average open rate for all niches hovers somewhere close to 10-25% , although this metric varies greatly with email type, industry, and many other factors. For transactional messages, the value below 50% should draw your immediate attention.
Click-through rate (CTR)
So you’ve delivered your emails, and people have opened them. But how many of them click on a link in your email to visit the web page you’re recommending? This important KPI is called the click-through rate (CTR). It measures the percentage of people who opened your email and clicked on at least one link in it.

For example, if 180 people opened your email and 9 clicked on a link, your click-through rate is 9/180 = 0.05 or 0.05 x 100 = 5%. The average click-through rate (CTR) is between 1.5% and 3%, but you can aim higher. You can take several steps to boost your click-through rates, such as personalization, segmentation, and mobile optimization.
Unsubscribe rate
People can unsubscribe from your mailing list for various reasons, e.g., they’re no longer interested in your content. Many legislations require businesses to include unsubscribe links in their emails in recognition of a recipient’s right to remove themselves from the mailing list.
The unsubscribe rate is the percentage of people who opt out of your mailing list from a specific message. For example, if you delivered 1000 emails and 5 people unsubscribed, your unsubscribe rate is 5/1000 = 0.005 or 0.005 x 100 = 0.5%.

A reasonable unsubscribe rate is less than 0.5%. Anything above this figure requires urgent attention, such as reducing the number of emails you send to avoid annoying subscribers.
Bounce rate
Bounce rate is the percentage of emails that don’t reach the intended recipients; it’s the inverse of your deliverability rate. For example, if you send 1000 emails, of which 200 are bounced back and don’t reach the intended recipients, your bounce rate is 200/1000 = 0.20, or 20%.

A healthy bounce rate for your email campaign is below 2%. 2% to 5% is a warning level, and anything above 5% is cause for concern.
If you haven’t sent any messages to a particular list for a substantial period, the number will be higher. Over one year, about 10% of all mailboxes det abandoned by their owners or become unreachable for other reasons.
The good news is that marketers can follow various proven steps to lower bounce rates. These steps include regularly scouring your mailing list to remove invalid addresses, using permission-based marketing, and setting up SPF and DKIM authentication to meet the requirements of mailbox providers.
Conversion rate
Conversion refers to someone taking an action you suggest in an email campaign. For example, you promote a product and place a “Buy Now” button that takes the email recipient to your website to buy the product. A person who follows this button and pays for the product counts as a “conversion.”
The conversion rate is the percentage of people who performed an action you specified in your email campaign. For example, if you deliver 200 emails to promote a new clothing item and 6 people place an order, your conversion rate is 6/200 = 0.03 or 0.03 times 100 = 3%.

The conversion rate is one of the most essential KPIs every email marketer must monitor. After all, the point of email marketing is to get your subscriber to take a specific action. It is also the most universal metric, being influenced by the greatest number of factors from SMTP server setup to email text and layout.
Spam complaint rate
Every email client lets users tag messages as spam, and any sender with too many reports may be blocked from sending further emails. Hence, keeping your spam complaint rate as low as possible is absolutely crucial.
The spam complaint rate is the percentage of email recipients that report it as spam. You need it to be lower than 0.1% to be in good standing with reputation services and mailbox providers. Any spam complaint rate above this level will likely reduce your deliverability.

Of course, the best way to keep spam complaint rates low is to avoid sending spam. However, even legitimate emails may get caught in false positives. Further steps to prevent this issue include cleaning your mailing lists, spacing your email sending frequency, and using a reputable email service provider, like UniOne.
Mailing list growth rate
No marketer wants their mailing list to remain static. Getting new subscribers opens up opportunities for more sales and encourages marketers to create more campaigns. The mailing list growth rate is self-explanatory: it’s the amount by which your number of subscribers grows over time.
This KPI measures the net increase in subscribers over a specific period. To calculate it, divide the number of net new subscribers by the total number of subscribers at the start of the period. Then, multiply the result by 100 to express it as a percentage.
Suppose you had 1,000 subscribers in January. 100 people unsubscribed throughout the year, leaving 900 subscribers. During the same period you got 500 new subscribers, making 1,400 by the end of the year. The number of net new subscribers is 1,400-1,000 = 400. Your mailing list growth rate is 400/1000 = 0.4 or 0.4 x 100 = 40%.
Revenue per email
This KPI quantifies the financial return from each email campaign. You calculate it by dividing the revenue from the campaign by the number of sent emails. For example, if you sent 500 emails and got $100, your revenue per email is $100/500 = $0.20.
This KPI indicates the monetary effectiveness of your email campaign. It tells you whether the campaign is financially worthwhile or if you’re better off deploying your marketing budget on another medium. The higher the revenue per email, the more effective your campaign is.
Revenue per subscriber
This KPI is very similar to revenue per email. You calculate revenue per subscriber by dividing the total revenue from several campaigns by the number of subscribers on your mailing list. Suppose you earned $1000 from a few campaigns sent to 5,000 subscribers: your revenue per subscriber will be $1000/5,000 = $0.2.
This KPI indicates an average subscriber’s financial value and helps you estimate how much you may spend to acquire a new subscriber.
Overall ROI
Measuring the return on investment (ROI) from your overall marketing campaign is most essential. This KPI is easy to understand although it doesn’t have a simple formula. The overall ROI is the revenue generated from all your email campaigns compared to what you’ve spent on them.
For example, if you spend $1,000 on a marketing campaign and generate $5,000 in sales, your ROI is $5000 - $1000 = $4,000 or 400%. However, calculating cost isn’t always straightforward. Should you include the cost of your marketing personnel? How about the cost of acquiring every email subscriber? The calculation varies for every business, and it’s crucial to differentiate recurring costs from one-time expenses.
Conclusion
Email marketing can be lucrative if done properly, and this involves monitoring essential KPIs. We’ve explained the significance of KPIs in email marketing and discussed the most important metrics you should know about. Every email marketer should invest their time in monitoring these KPIs to understand what needs to be improved in their marketing strategy. Above all, choose a reliable email service provider that lets you track these KPIs in real-time. Luckily, in UniOne all necessary data is available at your fingertips.