SLA calculator
Your SLA target, in allowed minutes.
An SLA percentage is hard to reason about on its own. This calculator converts any availability target into the actual downtime it allows per year, month, week, and day.
Scroll for the nines table
Reference
The standard nines table.
These are the commonly cited availability tiers and the downtime they allow per year, based on a 365-day, 8,760-hour year — the same year-length assumption used throughout this site.
Availability
Common name
Downtime per year
90%
"one nine"
36.5 days
95%
—
18.25 days
99%
"two nines"
3.65 days
99.5%
—
1.83 days
99.9%
"three nines"
8.76 hours
99.95%
—
4.38 hours
99.99%
"four nines"
52.6 minutes
99.999%
"five nines"
5.26 minutes
FAQ
SLA calculator, answered.
Questions that come up when translating an SLA percentage into a real number.
How is allowed downtime calculated from an SLA percentage?
Allowed downtime equals the total time in the period multiplied by the unavailable percentage (100 minus the SLA target). For a year, that is 8,760 hours multiplied by that fraction.
Why do the same SLA percentages appear on Wikipedia and vendor sites?
The nines table is standard math, not a proprietary benchmark — anyone calculating unavailable time from an SLA percentage over a 365-day year arrives at the same figures.
What SLA target should I choose?
That depends on your architecture and cost tolerance, not just ambition — each additional nine typically costs significantly more in redundancy and operational rigor than the one before it.
How does this relate to SLA credits?
This calculator shows the budget; the SLA credits calculator shows what you owe a customer when you miss it. For the revenue impact of missing it, see the cost of downtime calculator.
Next step
Know your budget. Now price a breach.
Once you know how much downtime your SLA allows, use the SLA credits calculator to see what a breach actually costs in contract terms.