An uptime SLA calculator converts service-level agreement percentages into allowed downtime windows. Enter an SLA like 99.99% to see exactly how many minutes of outage you are allowed per month or year - or work in reverse from an outage budget to the required SLA.
| Window | Allowed downtime |
|---|---|
| Per day | 1m 26.4s |
| Per week | 10m 4.8s |
| Per month (30.44 d) | 43m 50.0s |
| Per quarter (91.31 d) | 2h 11m 29s |
| Per year (365.25 d) | 8h 45m 58s |
Quick lookup for the most-quoted uptime targets and their implied outage budgets.
| SLA | Per year | Per month | Typical use case |
|---|---|---|---|
| 99% | 3d 15h 36m | 7h 18m | Basic shared hosting, internal tools, side projects. |
| 99.5% | 1d 19h 48m | 3h 39m | Small SaaS, B2B tools where short outages are tolerable. |
| 99.9% | 8h 45m | 43m 49s | Standard production SaaS - the most common SLA tier. |
| 99.95% | 4h 22m | 21m 54s | Business-critical SaaS, paid B2B platforms. |
| 99.99% | 52m 35s | 4m 23s | Major cloud services, payments, high-tier enterprise SaaS. |
| 99.999% | 5m 15s | 26.3s | Telecom, core infrastructure, financial trading systems. |
| 99.9999% | 31.5s | 2.6s | Carrier-grade, life-critical or military systems. |
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Open toolCommon questions about uptime SLAs, nines of availability, and translating percentages into real outage budgets.
An uptime SLA (service-level agreement) is a contractual promise about the percentage of time a service will be available. For example, a 99.9% SLA means the provider commits to no more than 0.1% downtime over the agreement period, typically a calendar month or year. Falling below the SLA usually triggers service credits or refunds.
A 99.9% uptime SLA allows roughly 43 minutes and 49 seconds of downtime per 30.44-day month, or about 8 hours and 45 minutes per year. This is the most common tier for production SaaS products.
Each additional 'nine' cuts the allowed downtime by a factor of ten. 99.9% (three nines) allows about 8.77 hours of downtime per year, while 99.99% (four nines) allows only 52.6 minutes per year. The infrastructure, redundancy, and on-call investment required to move from three to four nines is typically an order of magnitude greater.
Five nines refers to 99.999% availability, which permits only about 5 minutes and 15 seconds of downtime per year, or roughly 26 seconds per month. It is the standard for telecom, core network infrastructure, and financial trading systems where outages are extremely costly.
Divide the allowed downtime by the total time in the window, subtract from 1, and multiply by 100. For example, 43 minutes of allowed downtime per 30-day month = 1 - (43 / (30 * 24 * 60)) = 99.9%. The reverse mode in this calculator does the math for you in seconds, minutes, hours, or days.
Beyond calculators
Use the free SLA calculator for procurement and runbook math, then hand the actual reliability work to a full-stack AI developer for $2,500/month.
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