Calculate your email bounce rate in one click — completely free, no signup. See instantly whether your rate is healthy or about to get you throttled, and what to do about it.
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Tip: a healthy bounce rate is under 2%. Above 5% and ISPs start throttling you.
Bounce rate is the percentage of your emails returned undelivered. The lower the better — here are the bands every sender should know:
| Bounce rate | Assessment | What it means |
|---|---|---|
| < 2% | ✅ Excellent | Healthy. Mailbox providers reward you with inbox placement. |
| 2–5% | ⚠️ Acceptable | Watch it. Clean your list before the next campaign. |
| 5–10% | 🟠 Poor | ISPs are throttling you. Clean now. |
| > 10% | 🔴 Dangerous | Most ESPs suspend accounts at this rate. |
Bounce Rate = (Bounced Emails ÷ Total Emails Sent) × 100 Example: 350 bounces out of 10,000 sent = 3.5% bounce rate.
Both hard bounces (permanent — bad address) and soft bounces (temporary — full mailbox) count toward your total. Hard bounces hurt your sender reputation the most.
The single highest-impact step is verifying before you send. KillBounce gives you 100 free verifications to start — no card required.
Yes — completely free, no signup, no card. Just enter your numbers.
Any email returned undelivered — both hard bounces (permanent, bad address) and soft bounces (temporary, mailbox full). Both count toward your rate.
Most ESPs (Mailchimp, SendGrid) suspend or throttle accounts that consistently exceed 5–10%.
Verify your entire list before the next send and remove every invalid address. This alone usually drops bounce rate below 2%.
Sign up in under 30 seconds. Paste a list, hit verify, see the real SMTP-level result with a 0–100 deliverability score.
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