Uptime calculator: SLA & downtime
Enter an uptime percentage and see the downtime it allows per day, week, month, quarter and year. Or enter the downtime you had and get your uptime back, with the SLA tier it meets. It all runs in your browser, so nothing you type leaves the page.
Uptime to downtime
Type a percentage or pick a common SLA.
- Per day
- 1m 26s
- Per week
- 10m 5s
- Per month
- 43m 50s
- Per quarter
- 2h 11m 29s
- Per year
- 8h 45m 58s
Downtime to uptime
Enter the downtime you had and the period it fell in.
Uptime
99.8631%
Meets a 99.5% SLA, misses 99.9%.
A day is 24 hours and a week 7 days. A year is 365.25 days, so leap years average out, a month is a twelfth of it (30.44 days) and a quarter a fourth (91.31 days).
That is your budget.Uptime Monitoring tracks it.
It checks your site every minute on paid plans (every 5 minutes on Free), alerts you as soon as it stops answering, and shows your uptime, every outage with its cause, and when your SSL certificate and domain expire. Ask Theo, the AI assistant in the app, and it explains any finding in plain words.
Downtime for the common nines
How much downtime each uptime percentage allows, using the same average month (30.44 days) and year (365.25 days) as the calculator.
| Uptime | Per month | Per year |
|---|---|---|
| 90%One nine | 3d 1h 3m | 36d 12h 36m |
| 95% | 1d 12h 31m 30s | 18d 6h 18m |
| 99%Two nines | 7h 18m 18s | 3d 15h 39m 36s |
| 99.5% | 3h 39m 9s | 1d 19h 49m 48s |
| 99.9%Three nines | 43m 50s | 8h 45m 58s |
| 99.95% | 21m 55s | 4h 22m 59s |
| 99.99%Four nines | 4m 23s | 52m 36s |
| 99.999%Five nines | 26.3s | 5m 16s |
| 99.9999%Six nines | 2.6s | 31.6s |
What it checks
- Turns any uptime percentage into the downtime it allows per day, week, month, quarter and year
- Turns downtime over a period back into an uptime percentage
- Says which common SLA tier that uptime meets, from 99% to 99.999%
- Shows budgets under a second in milliseconds, so the higher nines never read as zero
What it does not
- It does not measure your site. The answer is only as good as the downtime you enter
- It uses average months and years. A 31-day month allows about 2% more downtime than shown, a 28-day month about 8% less
- It does not apply your SLA's own terms, such as excluded maintenance windows or a minimum outage length
- It does not work out service credits. Those come from your contract
Questions
What does 99.9% uptime mean?
The service is available 99.9% of the time, which leaves 0.1% for downtime: about 43m 50s a month, 8h 45m 58s a year or 1m 26s a day. It is often called "three nines".
How is uptime calculated?
Uptime is (total time − downtime) ÷ total time × 100. A monitor finds the downtime by requesting your site at a fixed interval and recording whether it answered, so the interval sets the resolution: with checks every 5 minutes, a 2-minute outage can fall between two checks.
What is the difference between an SLA, an SLO and an SLI?
An SLI (service level indicator) is the measurement, such as the share of checks that succeeded. An SLO (service level objective) is your internal target for it, such as 99.95% a month. An SLA (service level agreement) is the promise in a contract, usually set a little below the SLO, with service credits when it is missed.
How much does each extra nine matter?
Each nine cuts the allowed downtime tenfold. A month allows 43m 50s at 99.9%, 4m 23s at 99.99% and 26.3s at 99.999%, less than many deploys or restarts take, which is why targets that high usually need more than one server or region.
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