Uptime SLA Calculator
See exactly how much downtime a given SLA percentage allows per day, week, month, and year.
What the "nines" actually mean in real time
The difference between 99.9% and 99.99% uptime looks small — just 0.09 percentage points. In minutes, that's 43 minutes of downtime per month versus four and a half. One extra decimal digit divides the allowable downtime by ten. That's why SLA commitments are stated in percentages rather than vague terms like "high availability" — a percentage can be verified and converted to concrete time.
This calculator converts any uptime percentage into allowable downtime per day, week, month, and year. Useful when evaluating a cloud provider's SLA, planning your own SLA for customers, or simply understanding what the number in a contract actually means.
The 20 minutes between 99.9% and 99.95%
When you're choosing between hosting providers, one promises 99.9%, the other 99.95%. The calculator translates that into reality: the first can be down 43 minutes per month, the second just 22 minutes. If your service handles payments, those 20 minutes are the difference between an acceptable incident and chargebacks piling up.
The same applies when writing your own SLA. Before promising customers 99.99%, it's worth seeing that this is just 4 minutes per month. That includes planned updates, deployments, restarts — any moment the service was unavailable. Many teams overestimate their capabilities until they see the number in minutes.
Verify your SLA with real data
The calculator shows how much downtime an SLA allows. But to know whether you're meeting the target, you need real data. Uptime monitoring continuously checks availability and logs every incident. SLA reports turn that data into an actual uptime percentage for the period — a number you can compare against the commitment. The glossary breaks down the difference between SLA, SLO, and SLI if you want the full terminology picture.
Common SLA tiers
| SLA | Daily | Monthly | Yearly |
|---|---|---|---|
| 99% | 14m 24s | 7h 18m | 3d 15h 36m |
| 99.5% | 7m 12s | 3h 39m | 1d 19h 48m |
| 99.9% | 1m 26s | 43m 50s | 8h 45m 36s |
| 99.95% | 43s | 21m 55s | 4h 22m 48s |
| 99.99% | 8.6s | 4m 23s | 52m 34s |
| 99.999% | 0.86s | 26s | 5m 15s |