function calculateOpenRate() {
// 1. Get input values
var totalSentInput = document.getElementById('totalSent');
var bouncedInput = document.getElementById('bouncedEmails');
var opensInput = document.getElementById('uniqueOpens');
var resultDiv = document.getElementById('mcResult');
var errorDiv = document.getElementById('errorMsg');
// Parse values
var sent = parseInt(totalSentInput.value);
var bounced = parseInt(bouncedInput.value);
var opens = parseInt(opensInput.value);
// Reset display
errorDiv.style.display = 'none';
errorDiv.innerText = ";
resultDiv.style.display = 'none';
// 2. Validation Logic
if (isNaN(sent) || sent <= 0) {
errorDiv.innerText = "Please enter a valid number for Total Emails Sent.";
errorDiv.style.display = 'block';
return;
}
if (isNaN(bounced) || bounced < 0) {
bounced = 0; // Default to 0 if empty
}
if (isNaN(opens) || opens = sent) {
errorDiv.innerText = "Bounced emails cannot equal or exceed total emails sent.";
errorDiv.style.display = 'block';
return;
}
var delivered = sent – bounced;
if (opens > delivered) {
errorDiv.innerText = "Opens cannot exceed the number of delivered emails (Sent – Bounced).";
errorDiv.style.display = 'block';
return;
}
// 3. Calculation
// Formula: (Opens / Delivered) * 100
var openRate = (opens / delivered) * 100;
// 4. Determine Rating (Benchmarks vary, but ~21% is average generally)
var ratingText = "";
var ratingColor = "#333";
if (openRate = 15 && openRate < 25) {
ratingText = "Average";
ratingColor = "#f4b400"; // Yellow/Orange
} else {
ratingText = "Excellent";
ratingColor = "#0f9d58"; // Green
}
// 5. Update UI
document.getElementById('resDelivered').innerText = delivered.toLocaleString();
var rateElement = document.getElementById('resRate');
rateElement.innerText = openRate.toFixed(2) + "%";
rateElement.style.color = ratingColor;
var ratingElement = document.getElementById('resRating');
ratingElement.innerText = ratingText;
ratingElement.style.color = ratingColor;
resultDiv.style.display = 'block';
}
Understanding Mailchimp Open Rate Calculations
Email marketing remains one of the most effective channels for digital communication, and tracking your performance is vital. If you are using Mailchimp, the Open Rate is arguably the first metric you look at after hitting "Send". It tells you how many people actually viewed your message.
This calculator helps you verify your campaign data or project potential outcomes for future email blasts without needing to log into the dashboard.
The Mailchimp Open Rate Formula
Many beginners assume the open rate is simply the number of opens divided by the total number of emails sent. However, Mailchimp (and the industry standard) uses a slightly more specific formula to ensure accuracy. You must exclude emails that never reached the inbox (bounces).
Open Rate = (Unique Opens ÷ (Total Sent – Bounced)) × 100
Here is a breakdown of the variables:
Total Emails Sent: The total count of subscribers included in your campaign segment.
Bounced Emails: The number of emails that could not be delivered. This includes "Hard Bounces" (invalid addresses) and "Soft Bounces" (full mailboxes or temporary server issues).
Delivered Emails: This is calculated by subtracting Bounced Emails from Total Sent. This represents the actual audience that had the opportunity to open your mail.
Unique Opens: The count of individual subscribers who opened the email. If one person opens the email 10 times, it still counts as 1 unique open for the purpose of the open rate.
Calculation Example
Let's say you send a newsletter to 1,000 subscribers.
50 emails bounce because the addresses are old or invalid.
This leaves you with 950 Delivered Emails (1000 – 50).
Out of those 950, 210 people open the email.
The math works like this: (210 ÷ 950) = 0.221. Multiply by 100 to get the percentage.
Your Open Rate is 22.1%.
What is a Good Open Rate on Mailchimp?
Benchmarking your success is difficult because open rates vary wildly by industry. A hobbyist newsletter might see 50% open rates, while a daily deal e-commerce blast might be happy with 15%.
According to Mailchimp's global benchmarks across all industries, the average open rate hovers around 21.33%.
Government & Politics: ~28%
Non-Profit: ~25%
E-commerce: ~15-17%
Software & Technology: ~21%
If your calculator result is above 25%, you are performing exceptionally well. If it is below 15%, you may need to audit your subject lines or clean your email list.
Why Does Mailchimp Open Rate Matter?
The open rate is a gateway metric. If no one opens the email, no one clicks your links (CTR), and no one buys your product (Conversion Rate). Furthermore, consistently low open rates can signal to Email Service Providers (like Gmail or Outlook) that your content is irrelevant, which can eventually hurt your deliverability and send your future emails to the spam folder.
How to Improve Your Rate
Refine Subject Lines: Keep them under 60 characters, create curiosity, and A/B test frequently.
Segment Your List: Don't send every email to everyone. Targeted messages to specific interests always yield higher open rates.
Scrub Your List: Remove inactive subscribers who haven't opened an email in 6 months to improve your ratio.
Optimize Preheader Text: This is the snippet of text shown next to the subject line in an inbox. Use it as a secondary hook.