The Quick Answer
Email open rate measures the percentage of delivered emails that recipients opened, while click-through rate (CTR) measures the percentage that clicked a link inside the email.
The key formulas:
- Open Rate = (Unique Opens / Emails Delivered) x 100
- CTR = (Unique Clicks / Emails Delivered) x 100
- CTOR = (Unique Clicks / Unique Opens) x 100
- Conversion Rate = (Conversions / Emails Delivered) x 100
- Bounce Rate = (Bounced Emails / Emails Sent) x 100
- Unsubscribe Rate = (Unsubscribes / Emails Delivered) x 100
Each metric answers a different question about your email campaign's performance, from subject line effectiveness to content quality to business impact.
Worked Example: A Complete Campaign
A company sends a promotional email campaign. Here are the raw numbers:
| Metric | Count |
|---|---|
| Emails sent | 10,000 |
| Emails bounced | 500 |
| Emails delivered | 9,500 |
| Unique opens | 2,375 |
| Unique clicks | 285 |
| Conversions (purchases) | 42 |
| Unsubscribes | 19 |
Now calculate each metric:
Open Rate = (2,375 / 9,500) x 100 = 25.0%
CTR = (285 / 9,500) x 100 = 3.0%
CTOR = (285 / 2,375) x 100 = 12.0%
Conversion = (42 / 9,500) x 100 = 0.44%
Bounce Rate = (500 / 10,000) x 100 = 5.0%
Unsubscribe = (19 / 9,500) x 100 = 0.2%
What These Numbers Tell Us
- 25% open rate -- One in four recipients opened the email. This is in line with the all-industry average, suggesting the subject line and sender name were reasonably effective.
- 3% CTR -- Three percent of all recipients clicked a link. This is slightly above average, indicating the content and call to action resonated.
- 12% CTOR -- Of the people who opened the email, 12% clicked. This measures content quality independently of the subject line. A CTOR of 12% is solid.
- 0.44% conversion rate -- About 1 in 227 recipients made a purchase. This is typical for promotional emails.
- 5% bounce rate -- This is high. The industry target is under 2%. This list needs cleaning -- invalid addresses should be removed.
- 0.2% unsubscribe rate -- Within the normal range of 0.1-0.3%. No cause for concern.
What Each Metric Tells You
Each metric isolates a different part of the email marketing funnel:
| Metric | What It Measures | What Drives It |
|---|---|---|
| Open Rate | Did they open the email? | Subject line, sender name, send time, preview text |
| CTR | Did they click? | Content relevance, CTA clarity, offer strength |
| CTOR | Among openers, did they click? | Email body content quality, design, CTA placement |
| Conversion Rate | Did they take the desired action? | Landing page, offer, pricing, user experience |
| Bounce Rate | Did the email reach them? | List quality, email hygiene, data collection practices |
| Unsubscribe Rate | Did they opt out? | Content relevance, sending frequency, audience fit |
The critical insight: a low open rate means your subject line needs work. A high open rate but low CTR means people opened out of curiosity but the content did not deliver. A high CTR but low conversion means the email did its job but the landing page or offer did not.
Industry Benchmarks
Average email marketing metrics vary by industry. The following benchmarks are compiled from Mailchimp's industry data, Campaign Monitor, and Litmus:
| Industry | Open Rate | CTR | Unsubscribe Rate |
|---|---|---|---|
| All industries (average) | 20-25% | 2-3% | 0.1-0.3% |
| E-commerce / Retail | 15-18% | 2-3% | 0.2% |
| SaaS / Technology | 20-22% | 2-3% | 0.2% |
| Nonprofit / Government | 25-28% | 3-4% | 0.1% |
| Media / Publishing | 22-25% | 4-5% | 0.1% |
| Financial Services | 20-23% | 2-3% | 0.2% |
| Healthcare | 21-24% | 2-3% | 0.3% |
| Education | 23-26% | 3-4% | 0.1% |
These are approximate ranges. Your results depend on list size, audience quality, email type (newsletter vs. promotional vs. transactional), sending frequency, and many other factors. Compare your metrics against your own past performance first, then use industry benchmarks for broader context.
The Apple Mail Privacy Protection Problem
In September 2021, Apple introduced Mail Privacy Protection (MPP) with iOS 15. This feature fundamentally changed open rate tracking.
How it works: Apple Mail pre-fetches all email content -- including tracking pixels -- at the time of delivery, regardless of whether the user actually opens the email. This makes every Apple Mail recipient appear to have opened every email.
The impact:
- Apple Mail accounts for roughly 50-60% of all email opens, according to Litmus Email Client Market Share data
- Open rates for many senders jumped 10-20 percentage points after MPP launched
- The open rate metric is now inflated and less reliable as a true measure of engagement
What to do about it:
- Shift focus to clicks. CTR and CTOR, while affected by lower open count accuracy in the denominator, are more reliable engagement signals since clicks require deliberate user action.
- Segment Apple Mail users. Some email platforms can identify Apple Mail opens versus real opens, allowing you to calculate open rates for non-Apple users separately.
- Use open rate as a relative metric. Even if the absolute number is inflated, you can still compare open rates between campaigns sent to the same list. A subject line that gets 35% versus one that gets 28% is still performing better, even if both numbers are inflated.
- Track downstream metrics. Revenue per email, conversion rate, and website visits from email are unaffected by MPP and give you a clearer picture of campaign performance.
Delivered vs. Sent: Why the Denominator Matters
A subtle but important detail: most metrics use emails delivered (not emails sent) as the denominator. The difference is bounced emails.
Emails Delivered = Emails Sent - Bounced Emails
If you send 10,000 emails and 500 bounce, your delivered count is 9,500. Using "sent" as the denominator would artificially lower your rates because you are dividing by a larger number that includes emails that never reached anyone.
Types of bounces:
- Hard bounce: The email address is permanently invalid (does not exist, domain does not exist). Remove these immediately.
- Soft bounce: Temporary delivery failure (mailbox full, server temporarily down, message too large). Retry these, but remove after 3-5 consecutive failures.
A bounce rate above 2% signals list hygiene problems. Consistently high bounce rates damage your sender reputation, which can cause email providers to route your emails to spam folders.
Advanced Metrics
Beyond the basics, these metrics provide deeper insight:
Revenue Per Email (RPE)
RPE = Total Campaign Revenue / Emails Delivered
If a campaign delivered to 9,500 people generates $4,200 in sales: RPE = $4,200 / 9,500 = $0.44 per email.
RPE lets you calculate the monetary value of your email list and compare the revenue impact of different campaigns directly.
List Growth Rate
List Growth Rate = ((New Subscribers - Unsubscribes - Bounces) / Total List Size) x 100
A healthy list grows over time. If you add 300 subscribers but lose 50 to unsubscribes and 20 to bounces in a month on a list of 10,000: (300 - 50 - 20) / 10,000 x 100 = 2.3% monthly growth.
Spam Complaint Rate
Spam Complaint Rate = (Spam Complaints / Emails Delivered) x 100
This should be below 0.1% (1 complaint per 1,000 emails). Major email providers like Gmail and Yahoo monitor this rate. Exceeding their thresholds can result in your emails being blocked or sent to spam. Google's sender guidelines specify keeping spam complaint rates below 0.10% and never exceeding 0.30%.
Interpreting Your Results: A Diagnostic Framework
When analyzing a campaign, work through the funnel in order:
Step 1: Check deliverability. Is your bounce rate under 2%? If not, clean your list before analyzing other metrics.
Step 2: Evaluate opens. Is your open rate in line with your industry and past performance? If it has dropped, test different subject lines, sender names, or send times. Remember to account for Apple MPP inflation.
Step 3: Evaluate clicks. Is CTR where you expect it? If opens are fine but clicks are low, the problem is in the email body: the content, design, CTA, or offer. Check CTOR to confirm -- a low CTOR means the content is not compelling to people who bothered to open.
Step 4: Evaluate conversions. If CTR is healthy but conversions are low, the issue is post-click: the landing page, checkout process, or offer terms. The email did its job; the destination did not.
Step 5: Monitor list health. Watch unsubscribe rate and spam complaint rate over time. Upward trends signal fatigue or relevance problems.
Frequently Asked Questions
What is a good email open rate?
The all-industry average is approximately 20-25%. Nonprofits and education tend to be higher (25-28%), while e-commerce is typically lower (15-18%). Open rates above 25% are generally considered good. Keep in mind that Apple Mail Privacy Protection has inflated open rates since September 2021.
How is open rate tracked?
A tiny invisible image (tracking pixel) is embedded in the email. When the recipient's email client loads this image, it registers as an open. This method undercounts when images are blocked and overcounts when clients like Apple Mail pre-fetch images automatically.
Why are my open rates inflated?
Most likely due to Apple Mail Privacy Protection. Since iOS 15, Apple pre-fetches email content including tracking pixels for all Apple Mail users, making them appear to have opened every email. With Apple Mail holding 50-60% of the email client market, this significantly inflates open rate numbers.
What is the difference between CTOR and CTR?
CTR divides unique clicks by total emails delivered -- it measures how the full campaign performed. CTOR divides unique clicks by unique opens -- it measures how well the email content performed among people who actually opened it. CTR reflects the full funnel; CTOR isolates email body quality.
How do I improve click-through rate?
Use clear, prominent calls to action. Place the primary CTA above the fold. Minimize competing links. Personalize content for subscriber segments. Use button-style CTAs rather than plain text links. Optimize for mobile devices. Ensure the email delivers on the subject line's promise. Test variations systematically with A/B tests.
What is a good email bounce rate?
Below 2% is healthy. Above 5% indicates serious list quality issues. Remove hard bounces (invalid addresses) immediately after each send. Monitor soft bounces (temporary failures) and remove addresses after 3-5 consecutive soft bounces.
What is a good unsubscribe rate?
The average is 0.1-0.3% per email send. Rates consistently above 0.5% suggest problems with content relevance, frequency, or targeting. Some level of unsubscribing is healthy -- it naturally cleans your list of disengaged contacts.
How do I calculate revenue per email?
Revenue Per Email = Total Revenue from Campaign / Emails Delivered. A campaign generating $4,200 from 9,500 delivered emails has an RPE of $0.44. This metric connects email performance directly to business results.
Should I track open rate or click rate?
Track both, but rely more on click rate for decisions. Open rate is increasingly unreliable due to Apple Mail Privacy Protection. Click rate measures actual engagement -- the recipient deliberately took an action. CTOR is useful for isolating email content quality from subject line effectiveness.
What is email deliverability rate?
Deliverability rate = (Emails Delivered / Emails Sent) x 100. This measures how many sent emails were not bounced. True inbox placement (reaching the inbox versus spam folder) is a separate and harder-to-measure concept. Target a deliverability rate above 95%.
Related Tools
- Email Open Rate Calculator -- Calculate open rate from your campaign data
- Email Click-Through Rate Calculator -- Calculate CTR and CTOR for your email campaigns
- Conversion Rate Calculator -- Calculate conversion rate for any marketing channel
- A/B Test Duration Estimator -- Estimate how long to run an email A/B test for statistical significance