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About this tool
Convert an SLA uptime percentage into allowed downtime per day, week, month, quarter and year — and back.
This calculator converts an SLA availability percentage into the exact downtime it permits — allowed downtime = (1 − uptime% ÷ 100) × period length — reported per day, week, month, quarter and year. It is built for SREs, platform engineers and anyone negotiating or monitoring a service-level agreement, and it also works in reverse: enter real downtime to get the uptime percentage achieved. Periods use the Gregorian mean year of 365.2425 days so all five figures stay consistent.
Open SLA Uptime Downtime Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Daily, weekly, monthly, quarterly and yearly budgets from one percentage, mutually consistent.
Enter actual downtime minutes over any window and get the achieved uptime percentage.
One tap for 99%, 99.5%, 99.9%, 99.95%, 99.99% and 99.999% targets.
About 43 minutes 50 seconds per month and 8 hours 46 minutes per year. The formula is (1 − 0.999) × period length, using an average month of 30.44 days; per day it is roughly 1 minute 26 seconds.
Roughly a factor of ten in allowed downtime: 99.9% permits about 8.8 hours of outage per year while 99.99% permits about 52.6 minutes. Per month that is about 43.8 minutes versus 4.4 minutes, which is why each extra nine gets significantly more expensive to engineer.
Divide downtime by the total length of the period, subtract from 1 and multiply by 100: uptime% = 100 × (1 − downtime ÷ period). For example, 30 minutes of downtime in a 30.44-day month is 100 × (1 − 30 ÷ 43,829) ≈ 99.932%.
It depends on the contract — many providers measure per calendar month, so February has a smaller minute count than January. This tool uses the Gregorian average of 30.436875 days per month so the daily, monthly and yearly figures agree; check your SLA's own definition of the measurement window and any maintenance exclusions before relying on a figure.
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