What is a good email open rate?

The all-industry average sits around 21–22%. Anything above 25% is generally considered excellent; 15–21% is average; below 15% suggests problems with list quality, subject lines or send timing. Open rates vary significantly by sector: non-profits and finance routinely exceed 26%, while e-commerce and retail typically land at 15–18%.

How is the open rate calculated?

Open Rate = (Unique Opens / Emails Delivered) x 100. Delivered = Sent minus hard bounces. Using delivered — not sent — as the denominator is the correct industry standard because bounced emails never had a chance to be opened.

What is the difference between CTR and CTOR?

CTR (click-through rate) = Clicks / Delivered. It measures how many recipients who received the email clicked a link. CTOR (click-to-open rate) = Clicks / Unique Opens. CTOR isolates engagement quality — it tells you what fraction of people who actually opened the email then clicked. A high CTOR means your content resonates with openers; a low CTOR despite a high open rate suggests a weak offer or irrelevant content.

What counts as a statistically significant A/B result?

The calculator uses a two-proportion z-test (two-tailed, pooled standard error under the null hypothesis of equal rates). A p-value below 0.05 means there is less than a 5% chance the observed gap arose by random chance — this is the standard 95% confidence threshold. A z-score above 1.96 or below -1.96 also indicates significance. If the test is not significant, keep sending to a larger sample before picking a winner.

What bounce rate is acceptable for email?

Industry guidance is to keep hard bounce rate below 2%. Above 2% your sender reputation degrades and ESPs may throttle or suspend your account. Soft bounces (temporary delivery failures) are less critical but should be monitored. Remove hard-bounced addresses from your list immediately.

Why does Apple Mail Privacy Protection inflate open rates?

Since iOS 15, Apple Mail pre-fetches email content on behalf of users, triggering an open pixel even if the recipient never read the message. This can artificially inflate unique open counts by 20–40% for lists with high Apple Mail usage. The CTOR metric is now more reliable than raw open rate for evaluating engagement, because it is anchored in actual clicks which cannot be pre-fetched.

Email Open Rate Calculator

Email marketing metrics look straightforward on the surface — open rate is just opens divided by sends, right? In practice, the right denominator, the right definitions of “unique”, and the ability to compare against benchmarks make a real difference to decisions. This calculator computes every standard metric from a single set of inputs, explains the formula for each, and includes a full A/B significance test so you never declare a winner prematurely.

How it works

Enter the raw numbers from your email service provider (ESP) — sent, unique opens, unique clicks, bounces and unsubscribes — and the tool derives six campaign-level metrics instantly.

The six metrics and their formulas

Open rate is the headline number every marketer watches. The correct formula is:

Open Rate = Unique Opens / Delivered × 100

where Delivered = Sent − Hard Bounces. Dividing by delivered rather than sent is the industry standard, because a bounced email never reached an inbox and cannot possibly be opened.

Click-through rate (CTR) measures how many delivered recipients clicked any link:

CTR = Unique Clicks / Delivered × 100

Click-to-open rate (CTOR) is a quality metric that strips away the effect of deliverability and open-rate variation to isolate how compelling the content is for people who actually opened:

CTOR = Unique Clicks / Unique Opens × 100

A CTOR of 10–20% is typical. If your CTOR is low despite a healthy open rate, the email body or call-to-action is underperforming.

Bounce rate tracks hard delivery failures as a fraction of send volume:

Bounce Rate = Hard Bounces / Emails Sent × 100

Unsubscribe rate measures list fatigue or relevance issues:

Unsub Rate = Unsubscribes / Delivered × 100

Delivery rate confirms the health of your list and sender reputation:

Delivery Rate = Delivered / Sent × 100

Worked example

A SaaS company sends a product-update email to 10,000 subscribers. The ESP reports 2,150 unique opens, 430 clicks, 150 hard bounces and 26 unsubscribes.

Delivered: 10,000 − 150 = 9,850
Open rate: 2,150 / 9,850 = 21.83% (just above the all-industry average of 21.5%)
CTR: 430 / 9,850 = 4.37%
CTOR: 430 / 2,150 = 20.0% (strong — one in five openers clicked)
Bounce rate: 150 / 10,000 = 1.50% (within the 2% safe threshold)
Unsub rate: 26 / 9,850 = 0.26% (exactly at the industry average)

Benchmark comparison (SaaS / Technology): open rate is 21.83% vs 22.9% average, so marginally below sector. The CTOR of 20% is well above the typical 10–12%, suggesting the content performed strongly once recipients opened.

A/B test significance

When testing two subject lines, sending equal-sized splits and waiting for the difference to become statistically significant prevents false conclusions. The calculator uses a two-proportion z-test under the null hypothesis that both variants have equal true open rates.

The pooled standard error is:

SE = sqrt( p̂(1 − p̂)(1/n₁ + 1/n₂) )

where p̂ = (x₁ + x₂) / (n₁ + n₂) is the pooled proportion. The z-score is (p₁ − p₂) / SE, and the two-tailed p-value is derived from the standard normal distribution using an approximation of the complementary error function accurate to within 1.5 × 10⁻⁷.

A result is significant at p < 0.05 (z > 1.96 or z < −1.96). If your sample is still too small, the tool tells you to wait rather than pick a winner on noise.

Benchmark reference

The built-in benchmark table covers ten industries — from e-commerce (≈15.7% open) to finance (≈27.1% open) — based on aggregated data from Mailchimp and Campaign Monitor. Pick your sector from the dropdown to see exactly how many percentage points above or below average your campaign sits.