Quick answer
How do you calculate Email Open Rate?
Use Open rate = Unique opens ÷ Delivered emails × 100. Enter the matching values above to calculate the result instantly.
What it measures
Understanding Email Open Rate
Measure opens as a percentage of delivered marketing emails. Privacy protections and image preloading can record an open without a person intentionally reading the message.
Interpretation
What the result means
A 21% result means an open signal was recorded for 21 of every 100 delivered emails.
Action
How to use it
Use opens as a directional delivery and subject-line signal, then prioritize clicks, replies, and conversions.
Limits
What it leaves out
Open tracking is increasingly unreliable and should not be compared across tools without matching methodologies.
The math
Email Open Rate formula
Worked example
Example calculation
- Calculation
- 4,200 ÷ 20,000 × 100
- Result
- 21% open rate
Step by step
How to use this calculator
- 1Enter unique opens, delivered emails.
- 2Keep every input on the same time period and measurement basis.
- 3Review the result, then change one assumption at a time to test scenarios.
Decision support
When this calculator is useful
- Subject-line testing
- Deliverability monitoring
- Email trend reporting
Common questions
Frequently asked questions
Which inputs should I use for Email Open Rate?
Use unique opens, delivered emails, measured from the same source and period. Include only values that match the definitions shown beside each field.
Why might two Email Open Rate calculations differ?
The systems or accounting policies may define unique opens, delivered emails differently. Compare the time period, scope, source, and treatment of exceptional items before comparing results.
How often should I recalculate Email Open Rate?
Recalculate when any input changes materially and on the same reporting cadence used for the decision. Save the source and date of each input so the trend remains comparable.
Can I use Email Open Rate by itself?
No single metric captures the full decision. Use the result with the related measures, assumptions, and limitations shown on this page.
Calculation reviewed: 2026-06-18. CalcPilot uses the formula shown above and tests representative values during the production build. See our methodology and correction policy.
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