Uptime Calculator
99.9% sounds great. See what it means in real hours and minutes — before you sign up.
Common SLA tiers
| Period | Total time | Allowed downtime |
|---|---|---|
SLA tier comparison
| SLA | Nines | Per year | Per month | Typical tier |
|---|---|---|---|---|
| 99% | 2 nines | 3d 15h 36m | 7h 18m | Budget shared hosting |
| 99.5% | — | 1d 19h 48m | 3h 39m | Standard shared hosting |
| 99.9% | 3 nines | 8h 45m | 43m 48s | Most managed hosts |
| 99.95% | — | 4h 22m | 21m 54s | Managed cloud (entry) |
| 99.99% | 4 nines | 52m 35s | 4m 21s | Enterprise / dedicated |
| 99.999% | 5 nines | 5m 15s | 26s | Carrier-grade / CDN |
Pro tips
What SLA marketing doesn't tell you.
📋 SLA credits rarely cover real losses
Most SLA credits are 1 day of service credit per hour of downtime — a fraction of what an hour of downtime actually costs a business. The credit is a goodwill gesture, not compensation. The real value of a strong SLA is what it signals about infrastructure investment.
🔍 Scheduled maintenance is usually excluded
Most providers exclude "scheduled maintenance" from their uptime calculations as long as they give 24–72 hours notice. Read the definition of "downtime" in the SLA carefully — it's often narrower than you'd expect.
📊 Monitor it yourself — don't trust the provider
Never rely solely on a provider's status page to know when you're down. Use an independent monitoring service like UptimeRobot (free for 5-minute checks) or Better Uptime. This also gives you evidence if you need to file an SLA claim.
💰 The cost of downtime scales with traffic
For a site doing $10,000/month in revenue, one hour of downtime costs roughly $14. At 99.9% SLA, that's potentially $122/year in lost revenue from SLA-allowed downtime. For high-traffic e-commerce, the gap between 99.9% and 99.99% is worth paying for.
📝 File claims within the window or lose them
Most providers require SLA claims within 24–72 hours of the incident. If you don't file, you get nothing. Set a reminder whenever you experience significant downtime and document the start/end time from your own monitoring, not theirs.
🏗 Uptime ≠ performance
100% uptime with a 10-second load time is worse than 99.9% uptime with a 200ms load time for most users. SLA guarantees only cover availability, not speed. Always check both uptime guarantees and real-world performance data.
Compare hosts by uptime guarantee
See which providers offer 99.99% SLAs and how their guarantees are worded.