body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
}
.calculator-container {
background: #f9fafb;
border: 1px solid #e5e7eb;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calculator-title {
font-size: 24px;
font-weight: 700;
margin-bottom: 20px;
color: #111827;
text-align: center;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #374151;
}
.input-group input {
width: 100%;
padding: 12px;
border: 1px solid #d1d5db;
border-radius: 6px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.input-group input:focus {
outline: none;
border-color: #3b82f6;
box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}
.calculate-btn {
width: 100%;
background-color: #3b82f6;
color: white;
padding: 14px;
border: none;
border-radius: 6px;
font-size: 16px;
font-weight: 600;
cursor: pointer;
transition: background-color 0.2s;
}
.calculate-btn:hover {
background-color: #2563eb;
}
.results-container {
margin-top: 25px;
padding: 20px;
background-color: #fff;
border: 1px solid #e5e7eb;
border-radius: 6px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
padding-bottom: 12px;
border-bottom: 1px solid #f3f4f6;
}
.result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
color: #6b7280;
font-weight: 500;
}
.result-value {
font-weight: 700;
color: #111827;
}
.main-result {
font-size: 1.25em;
color: #3b82f6;
}
.article-content {
margin-top: 40px;
}
h2 {
font-size: 22px;
margin-top: 30px;
margin-bottom: 15px;
color: #1f2937;
}
h3 {
font-size: 18px;
margin-top: 20px;
margin-bottom: 10px;
color: #374151;
}
p {
margin-bottom: 15px;
}
ul {
margin-bottom: 15px;
padding-left: 20px;
}
li {
margin-bottom: 8px;
}
.formula-box {
background: #eff6ff;
padding: 15px;
border-left: 4px solid #3b82f6;
font-family: monospace;
margin: 20px 0;
font-size: 16px;
}
.error-msg {
color: #ef4444;
font-size: 14px;
margin-top: 5px;
display: none;
}
function calculateOpenRate() {
// Get input values
var sentInput = document.getElementById('emailsSent').value;
var bouncedInput = document.getElementById('emailsBounced').value;
var openedInput = document.getElementById('emailsOpened').value;
var resultsDiv = document.getElementById('results');
var errorDiv = document.getElementById('errorDisplay');
// Reset display
resultsDiv.style.display = 'none';
errorDiv.style.display = 'none';
errorDiv.innerHTML = ";
// Validate inputs
if (sentInput === " || bouncedInput === " || openedInput === ") {
errorDiv.innerHTML = 'Please fill in all fields.';
errorDiv.style.display = 'block';
return;
}
var sent = parseFloat(sentInput);
var bounced = parseFloat(bouncedInput);
var opened = parseFloat(openedInput);
// Logic validation
if (isNaN(sent) || isNaN(bounced) || isNaN(opened)) {
errorDiv.innerHTML = 'Please enter valid numbers.';
errorDiv.style.display = 'block';
return;
}
if (sent = sent) {
errorDiv.innerHTML = 'Bounced emails cannot equal or exceed total emails sent.';
errorDiv.style.display = 'block';
return;
}
if (opened > (sent – bounced)) {
errorDiv.innerHTML = 'Opened emails cannot exceed the number of delivered emails.';
errorDiv.style.display = 'block';
return;
}
// Calculations
var delivered = sent – bounced;
var openRate = (opened / delivered) * 100;
var bounceRate = (bounced / sent) * 100;
// Display Results
document.getElementById('resSent').innerHTML = sent.toLocaleString();
document.getElementById('resDelivered').innerHTML = delivered.toLocaleString();
document.getElementById('resBounceRate').innerHTML = bounceRate.toFixed(2) + '%';
document.getElementById('resOpenRate').innerHTML = openRate.toFixed(2) + '%';
resultsDiv.style.display = 'block';
}
How is Email Open Rate Calculated?
Understanding the performance of your email marketing campaigns relies heavily on one key metric: the Open Rate. However, many marketers misunderstand the math behind this number. It is not simply the number of opens divided by the number of emails you hit "send" on. To get an accurate picture of engagement, you must account for deliverability.
The Email Open Rate Formula
The standard industry formula for calculating email open rate takes into account only the emails that actually landed in an inbox. Bounced emails (those rejected by the server due to invalid addresses or full inboxes) are excluded from the equation.
Open Rate = (Unique Opens ÷ (Total Emails Sent – Bounced Emails)) × 100
Here is a breakdown of the variables:
- Unique Opens: The count of individual subscribers who opened your email. If one person opens the email five times, it still counts as one unique open.
- Total Emails Sent: The raw number of contacts included in your campaign list.
- Bounced Emails: The number of emails that could not be delivered (both hard bounces and soft bounces).
Step-by-Step Calculation Example
Let's look at a realistic scenario to see how the math works in practice:
- You send a newsletter to 10,000 subscribers.
- Your report shows that 200 emails bounced (were not delivered).
- Your analytics show 2,450 unique opens.
First, calculate the number of Delivered emails:
10,000 (Sent) - 200 (Bounced) = 9,800 Delivered
Next, divide the unique opens by the delivered count:
2,450 ÷ 9,800 = 0.25
Finally, multiply by 100 to get the percentage:
0.25 × 100 = 25% Open Rate
Why We Exclude Bounces
If you included bounced emails in the denominator, you would be penalizing your engagement metrics for deliverability issues. The open rate is intended to measure the effectiveness of your Subject Line and Sender Name. A recipient cannot open an email they never received; therefore, undelivered emails should not count against your open performance.
What is a "Good" Open Rate?
Benchmarks vary significantly by industry, but generally speaking:
- 15% – 25%: Considered a healthy average for most industries.
- Above 25%: Excellent performance indicating high list affinity.
- Below 15%: Indicates potential issues with subject lines, list hygiene, or sender reputation.
Total Opens vs. Unique Opens
Most Email Service Providers (ESPs) track both "Total Opens" and "Unique Opens." For the purpose of calculating your rate, you should almost always use Unique Opens. Total opens can be skewed if a single subscriber forwards your email or re-opens it multiple times on different devices. Using total opens would inflate your success metrics artificially.