SLA & Uptime Calculator
Convert any SLA percentage into the allowed downtime per day, week, month, quarter and year — and see the classic nines reference table from 99% to 99.999%.
| SLA | Per day | Per month | Per year |
|---|---|---|---|
| 99% | 14m 24s | 7h 18m 18s | 3d 15h 39m |
| 99.9% | 1m 26s | 43m 50s | 8h 45m 58s |
| 99.95% | 43s | 21m 55s | 4h 22m 59s |
| 99.99% | 9s | 4m 23s | 52m 36s |
| 99.999% | 1s | 26s | 5m 16s |
What SLA percentages mean
An SLA (Service Level Agreement) expresses availability as a percentage of a time window. Because the window is fixed, a small change in the percentage translates into a large change in tolerated downtime: 99% allows more than 3 days of downtime per year, while 99.999% (“five nines”) allows just over 5 minutes. This calculator converts any percentage you enter into the concrete downtime budget for each period.
Downtime per 9s (99% to 99.999%)
Each additional nine cuts your allowed downtime by roughly 10x. The reference table above shows the standard tiers side by side so you can pick a realistic target. Most SaaS products commit to 99.9% externally while running a tighter 99.95% or 99.99% internally.
How to calculate your SLA
Take your unavailability fraction, (100 − uptime) / 100, and multiply it by the seconds in the period. For 99.9% over a 30-day month that is 0.001 × 2,629,800s ≈ 2,630s, about 43 minutes 50 seconds — exactly what the tool reports.
SLA vs SLO vs SLI
The SLA is the external contract; the SLO is your internal target and the SLI is the metric you actually measure. Teams keep the SLO stricter than the SLA to leave headroom before penalties trigger. For the full breakdown see our SLI vs SLO vs SLA SRE guide.
Error budgets
The complement of your SLO is your error budget — the unreliability you are allowed to spend on shipping features before you must freeze releases and stabilize. A 99.9% SLO gives a 0.1% budget. Learn how to operate one in our error budgets SRE guide.
FAQ
What does 99.9% uptime mean?
A 99.9% SLA (three nines) allows 0.1% downtime, which is about 43 minutes 50 seconds per month or roughly 8 hours 45 minutes per year. It is the most common SLA tier for SaaS products.
How much downtime is 99.99% uptime?
Four nines (99.99%) permits about 4 minutes 23 seconds of downtime per month, or about 52 minutes 36 seconds per year. Reaching it usually requires redundancy and automated failover.
What is the difference between an SLA, SLO and SLI?
An SLI is the measured indicator (e.g. success rate), an SLO is the internal target for that indicator, and an SLA is the external contract with financial penalties. The SLA target is usually looser than the SLO to give engineering headroom.
What is an error budget?
The error budget is 100% minus your SLO. At a 99.9% SLO you have a 0.1% error budget, the allowed unreliability you can spend on releases and risk before you must freeze changes and focus on stability.