Uptime & SLA Calculator
Convert an uptime guarantee into real time: how many minutes of downtime does 99.9% actually allow per month? Enter any SLA or pick a preset.
| SLA | Daily | Monthly (30d) | Yearly |
|---|---|---|---|
| 99% | 14.4 minutes | 7.2 hours | 3.7 days |
| 99.5% | 7.2 minutes | 3.6 hours | 1.8 days |
| 99.9% | 1.4 minutes | 43.2 minutes | 8.8 hours |
| 99.95% | 43 seconds | 21.6 minutes | 4.4 hours |
| 99.99% | 8.6 seconds | 4.3 minutes | 52.6 minutes |
| 99.999% | 0.9 seconds | 26 seconds | 5.3 minutes |
Reading the nines
Each added nine cuts allowed downtime by 10×. 99% (two nines) permits over 7 hours of downtime a month; 99.9% (three nines) about 43 minutes; 99.99% (four nines) about 4.3 minutes; and 99.999% (five nines) just 26 seconds. Most shared hosting and standard cloud SLAs sit at 99.9–99.95%; five nines is realistic only for redundant, multi-region architectures.
Check how the provider measures it too: monthly vs yearly windows, whether scheduled maintenance counts, and what the SLA credit actually pays out — often just a partial refund of that month's fee.
Error budgets: the SRE view
Site reliability engineering flips the SLA around: if you promise 99.9%, you have a monthly "error budget" of ~43 minutes to spend on incidents, deploys gone wrong, and maintenance. Teams that track the budget deploy freely while there's budget left and freeze risky changes when it's exhausted — turning reliability into an explicit engineering trade-off instead of an aspiration.
Frequently asked questions
How much downtime is 99.9% uptime?
About 43 minutes 12 seconds per 30-day month, 8 hours 46 minutes per year, or 1 minute 26 seconds per day.
How much downtime is 99.99% uptime?
About 4 minutes 19 seconds per 30-day month or 52 minutes 36 seconds per year.
What is an error budget?
The downtime your SLA allows, treated as a budget you can spend: at 99.9% monthly you can 'afford' ~43 minutes of incidents. Exceeding it means freezing risky changes until reliability recovers.
Is a 100% uptime SLA real?
No system achieves literal 100%. A 100% SLA is a billing promise — the provider pays credits for any downtime — not a technical guarantee. Read the credit schedule to see what it's worth.
This tool provides estimates for educational purposes only and does not constitute professional advice.