Calculate Allowed Downtime
Enter your SLA percentage to see how much downtime is allowed per month, quarter, and year.
Common SLA Uptime Levels
Here's what different uptime percentages mean in practice:
| SLA | Daily | Weekly | Monthly | Yearly |
|---|---|---|---|---|
| 99% | 14m 24s | 1h 40m 48s | 7h 18m 17s | 3d 15h 39m |
| 99.5% | 7m 12s | 50m 24s | 3h 39m 8s | 1d 19h 49m |
| 99.9% | 1m 26s | 10m 4s | 43m 49s | 8h 45m 57s |
| 99.95% | 43s | 5m 2s | 21m 54s | 4h 22m 58s |
| 99.99% | 8.6s | 1m 0s | 4m 23s | 52m 35s |
| 99.999% | 0.86s | 6s | 26s | 5m 15s |
Key insight: The difference between 99.9% and 99.99% seems small, but it's the difference between 43 minutes of downtime per month vs 4 minutes. For critical systems, those extra 39 minutes matter.
How SLA Uptime is Calculated
The formula for allowed downtime is simple:
Downtime = Total Time × (1 - SLA%)
Example: 99.9% SLA
- Per day: 24 hours × 60 minutes × 0.001 = 1.44 minutes
- Per month: 30 days × 24 hours × 60 minutes × 0.001 = 43.2 minutes
- Per year: 365 days × 24 hours × 60 minutes × 0.001 = 525.6 minutes (8h 45m)
What Counts as Downtime?
SLA definitions vary by provider. Common exclusions include:
- Scheduled maintenance — Often excluded from SLA calculations
- Force majeure — Natural disasters, ISP failures
- User-caused issues — Misconfiguration, exceeded quotas
- Third-party dependencies — Some providers exclude these
Read the fine print: A 99.9% SLA that excludes scheduled maintenance is very different from one that includes all downtime. Always check what's actually covered.
SLA Credits vs. Real Costs
Most providers offer service credits when SLAs are missed:
| Typical SLA Credit Structure | Credit |
|---|---|
| Uptime 99.0% - 99.9% | 10% of monthly bill |
| Uptime 95.0% - 99.0% | 25% of monthly bill |
| Uptime below 95.0% | 50-100% of monthly bill |
Reality check: A 50% credit on a $100/month service doesn't compensate for lost customers during a 2-day outage. SLAs protect the provider more than the customer.
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