Uptime and SLA downtime calculator

99.9% uptime allows 43 minutes 50 seconds of downtime in an average month; 99.99% allows 4 minutes 23 seconds. Enter any SLA level to see its downtime budget per day, week, month, quarter and year, or enter the downtime you measured to get your uptime.

Allowed downtime per average month (30.44 days)

43m 50s

at 99.9% uptime

Day: 1m 26s
Week: 10m 5s
30-day month: 43m 12s
Average month (30.44 days): 43m 50s
Quarter (91.31 days): 2h 11m 29s
Year (365.25 days): 8h 45m 58s

App Maintenance Plans: from ₹20,000 / $350 a month

Every app maintenance plan includes uptime monitoring with alerts to us, during Indian working hours. We don't offer 24/7 on-call cover.

Ask about the App Maintenance Plans What the App Maintenance Plans includes

How is allowed downtime calculated?

Allowed downtime is the share of the period the SLA lets you be down: (100 − uptime %) ÷ 100 × the length of the period. At 99.9% that is 0.1% of the period, which is 86.4 seconds a day or 43 minutes 50 seconds in an average month.

Months are not all the same length, so a monthly SLA allows a little more downtime in a 31-day month than in February. This calculator shows a 30-day month and an average month of 30.44 days (a 365.25-day year divided by 12); check which one your contract uses.

Services in a chain multiply. If a page needs three services and each is up 99.9% of the time, the page is up at most 99.9% × 99.9% × 99.9% = 99.7%, which is about 2 hours 11 minutes a month rather than 44 minutes.

allowed downtime = (1 − uptime ÷ 100) × period length
chained uptime = uptime₁ × uptime₂ × … × uptimeₙ

How much downtime does each uptime level allow?

Allowed downtime by SLA level (average month = 30.44 days, year = 365.25 days)
Uptime	Per day	Per week	Per month	Per year
90%	2h 24m	16h 48m	3d 1h 3m	36d 12h 36m
95%	1h 12m	8h 24m	1d 12h 31m 30s	18d 6h 18m
99%	14m 24s	1h 40m 48s	7h 18m 18s	3d 15h 39m 36s
99.5%	7m 12s	50m 24s	3h 39m 9s	1d 19h 49m 48s
99.9%	1m 26s	10m 5s	43m 50s	8h 45m 58s
99.95%	43s	5m 2s	21m 55s	4h 22m 59s
99.99%	9s	1m	4m 23s	52m 36s
99.999%	1s	6s	26s	5m 16s

How to work out an SLA's downtime budget

1
Choose what to work outPick the downtime an SLA allows, or the uptime that follows from downtime you measured.
2
Enter the uptime target or the downtimeType the SLA percentage, such as 99.9, or the minutes of downtime from your monitoring.
3
Pick the period and the chainChoose day, week, month, quarter or year, and how many services must all be up for the page to work.
4
Read the budgetThe result shows the downtime allowed for every period and whether a measured month met 99%, 99.9%, 99.95% and 99.99%.

Frequently asked questions

How much downtime does 99.9% uptime allow a month?

43 minutes 50 seconds in an average month of 30.44 days, or 43 minutes 12 seconds in a 30-day month. Over a year it is 8 hours 45 minutes 58 seconds.

What is the difference between 99.9% and 99.99% uptime?

Ten times less downtime: 99.99% allows 4 minutes 23 seconds in an average month against 43 minutes 50 seconds at 99.9%. The extra nine usually means automatic failover and someone on call at all hours, which is why it costs far more to run.

Does planned maintenance count against an SLA?

Only if the contract says so. Many SLAs exclude announced maintenance windows from the downtime count, so read the definition of downtime in the agreement before comparing numbers.

Why is my app's uptime lower than my hosting provider's?

Because the app depends on more than the host. If the server, the database and the login provider are each up 99.9% of the time, the app is up at most about 99.7%, so its downtime budget is roughly three times the host's.

Is 100% uptime possible?

Not as a promise. Every system has updates, provider incidents and network faults. SLAs promise a percentage and a credit when it is missed; 100% here only describes a period that happened to have no measured downtime.

Built and maintained by CountryDevs. Updated October 2026. Runs in your browser; what you type is not sent to us.

Related tools

See all 73 free tools

Building a SaaS product?

We design, build, and scale SaaS platforms — from auth and billing to dashboards and APIs.

See SaaS services Start a project

Built by CountryDevs · No signup · No ads · We count visits, never what you enter