Definition
Time to conversion is the average number of hours or days between when a campaign is sent and when subscribers complete the target action — typically a purchase, sign-up or download. This metric reveals how quickly your email content drives action and helps calibrate everything from follow-up campaign timing to attribution windows.
A short time to conversion indicates strong offer alignment and high purchase intent. A longer time may suggest a considered purchase decision where multiple touchpoints are required.
How to Calculate It
For each converting subscriber, calculate the difference between the email send timestamp and the conversion timestamp. Average these values across all converting subscribers per campaign. Segment by campaign type — promotional campaigns often have shorter times than educational newsletters — and by device, as mobile conversions frequently happen within hours of send while desktop conversions may take longer.
Best Practices
- Use time-to-conversion data to set your attribution window — if most conversions happen within 48 hours, credit events beyond that window are likely unrelated
- Segment by purchase category; high-consideration products naturally have longer times and should not be judged by the same standard as impulse purchases
- Compare time to conversion across subject-line and CTA variants to see which messaging drives faster action
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
ARPU (Average Revenue Per User)
ARPU (Average Revenue Per User) is a metric that measures the average revenue generated per email subscriber over a specific period, used to evaluate list value and campaign effectiveness.
Attention Rate
Attention rate is the percentage of email opens that last longer than 5 seconds, distinguishing genuine reads from passive opens, preview-pane views, or Apple MPP auto-loads.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.
Campaign Internal Rate of Return (IRR)
Campaign IRR is the annualised return rate earned by an email campaign, accounting for the timing and magnitude of costs and revenue across the campaign's full lifecycle.
Campaign Lifted Revenue
Campaign lifted revenue is the additional revenue generated by an email campaign beyond what would have occurred without it, measured via a holdout group or statistical lift analysis.