What is email bounce rate?
Email bounce rate is the share of sent emails that could not be delivered and were returned. It splits into hard bounces, permanent failures like a dead address, and soft bounces, temporary issues like a full inbox. It is a different metric from the web bounce rate used in analytics, which measures single-page website visits. This one is purely about email deliverability.
The formula.
Email bounce rate = (bounces divided by sent) times 100. Count both hard and soft bounces against everything you sent. Watch hard bounces most closely. They mean the address is invalid, and repeated sends to invalid addresses are what damage your reputation with mailbox providers.
A worked example.
You send 2,000 emails and 30 bounce. The bounce rate is 30 divided by 2,000, times 100, which is 1.5%.
What is a good email bounce rate?
Keep it under 2%. This is one metric where lower is unambiguously better, since bounces signal a stale or poorly collected list. Between 2 and 5% is worth investigating, and above 5% actively harms deliverability and inbox placement.
How to lower it.
Use double opt-in, remove hard-bouncing addresses promptly, and avoid buying or scraping lists. A smaller list of valid, engaged addresses outperforms a large dirty one.