ObserveifyNow Open workspace

Uptime and downtime budget calculator

Turn an availability target into permitted downtime, or check the uptime implied by a recorded outage. Free, account-free arithmetic in your browser.

Choose one observation period

No URL probing or remote monitoring. Inputs stay on this page and are not saved. Downloading creates a local text file.

Fixed elapsed time: 1 day = 24 hours. Choose the actual month/year length, or a custom duration from 1 second to 36,600 days. No calendar dates or daylight-saving adjustment.

Target: 0–100%. Use a decimal point, up to 9 decimal places; no thousands separators.

Check recorded downtime in that period

Use 0 for no recorded downtime. Count overlapping outages once for a single service; include only time inside this period.

Worked example: 99.9% target, 30 days, 30 minutes of actual downtime.

Permitted downtime

43 min 12 s

2,592 seconds permitted in 2,592,000 seconds, at 99.9%.

Observed uptime

99.930555556%

From 30 min of downtime in the same period.

Remaining budget: 13 min 12 s.

The budget is a calculated target, not measured availability or an SLA guarantee. Observed uptime uses the downtime you enter; this tool does not verify monitoring coverage. Displayed results are rounded.

Formulas and units

Permitted downtime = observation period × (1 − target availability / 100).

Observed uptime (%) = (1 − actual downtime / observation period) × 100.

Convert both durations to the same unit first. One minute is 60 seconds, one hour is 3,600 seconds, and one fixed day is 86,400 seconds. A 30-day window has 2,592,000 seconds. A 365-day year has 31,536,000; a 366-day year has 31,622,400.

This is a time-based calculation for one defined service. Request success ratios, scheduled service hours and contractual exclusions require their own denominator. Unknown monitoring time is not evidence of uptime.

What do 99.9% and 99.99% allow?

Permitted downtime for fixed elapsed periods
Target 1 day 30 days 365 days
99% 14 min 24 s 7 h 12 min 3 d 15 h 36 min
99.9% 1 min 26.4 s 43 min 12 s 8 h 45 min 36 s
99.99% 8.64 s 4 min 19.2 s 52 min 33.6 s
99.999% 0.864 s 25.92 s 5 min 15.36 s

At 99.9% over 30 days: 2,592,000 × 0.001 = 2,592 seconds, or 43 minutes 12 seconds. At 99.99%: 2,592,000 × 0.0001 = 259.2 seconds, or 4 minutes 19.2 seconds.

With a 30-minute outage in that same window: (1 − 1,800 / 2,592,000) × 100 ≈ 99.930555556%. That meets a 99.9% time target and exceeds a 99.99% downtime budget. A yearly budget cannot excuse a missed monthly target.

Read the guide to measurement windows, outage accounting and published Uptime Kuma status pages.