Free tool
SLA uptime calculator
Convert any SLA percentage to allowed downtime per day, week, month, quarter, and year. With reverse calc, cost calc, and a nines breakdown.
Step 1 · Input
SLA → allowed downtime
Enter an SLA percentage. See the maximum allowed downtime per period.
Step 1 · Output
Max downtime allowed
| Per period | Allowed downtime |
|---|---|
Daily 24h | 1m 26s |
Weekly 7d | 10m 5s |
Monthly 30d | 43m 12s |
Quarterly 90d | 2h 9m 36s |
Yearly 365d | 8h 45m 36s |
Step 2 · Input
Downtime → equivalent SLA
Enter how much downtime you had and over what period. We'll back out the SLA you actually delivered.
Step 2 · Output
SLA delivered
That's around two nines.
Step 3 · Input
Downtime → dollar cost
Put a number on what an outage costs you.
Step 3 · Output
Total cost
At $5,000/hr of downtime, catching the outage a minute sooner saves about $5,000 per outage.
Reference
Common SLA targets
| SLA | Nines | Per day | Per month | Per year |
|---|---|---|---|---|
| 99% | two nines | 14m 24s | 7h 12m | 3d 15h 36m |
| 99.5% | two nines | 7m 12s | 3h 36m | 1d 19h 48m |
| 99.9% | three nines | 1m 26s | 43m 12s | 8h 45m 36s |
| 99.95% | three nines | 43s | 21m 36s | 4h 22m 48s |
| 99.99% | four nines | 9s | 4m 19s | 52m 34s |
| 99.999% | five nines | 1s | 26s | 5m 15s |
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Background
What an SLA actually means
An SLA (Service Level Agreement) percentage tells you the uptime guarantee a provider commits to over a billing period. The complement — what's left after you subtract the percentage from 100% — is the maximum allowed downtime. Three nines (99.9%) means up to 8 hours 45 minutes of downtime per year. Four nines (99.99%) drops that to about 52 minutes. Five nines (99.999%) gives you only about 5 minutes per year.
SLAs are useful for setting expectations, but they don't catch outages on their own. You need monitoring that fires more often than your SLA budget so you actually notice when you're burning it. A check every 5 minutes can burn 5 minutes of error budget before alerting; a check every minute keeps the surprise to ~60 seconds.
Targets in the wild
Common SLA targets
99% is loose (~3.65 days/year of downtime). 99.9% is the most common SaaS target. 99.95% and 99.99% are common for production tiers of paid services. 99.999% — "five nines" — is rare outside of telecom and payments infrastructure; achieving it requires multi-region failover and synthetic monitoring at sub-minute cadence.
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