Uptime Calculator

Enter how much downtime a system had during a day, week, month, quarter, or year to calculate uptime percentage, see how it stacks up against standard SLA "nines" tiers, and view the annualized downtime equivalent.

Quick Facts

Uptime formula
Uptime % = (Total time − Downtime) ÷ Total time × 100
Downtime and total time must be measured over the same period.
SLA "nines" reference
99% ≈ 3.65 days/yr · 99.9% ≈ 8.76 hr/yr · 99.99% ≈ 52.6 min/yr
Based on a 365-day year; each extra "nine" cuts allowed downtime roughly tenfold.

Your Results

Calculated
Uptime percentage
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Over the selected period
Downtime this period
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Entered downtime vs. total time
Nearest SLA tier
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Standard "nines" classification
Annualized downtime
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This rate projected over 1 year

Ready

Choose a period, enter downtime, then press Calculate.

Understanding the Uptime Calculator

Uptime is the share of a time period a system, service, or piece of equipment was actually available, expressed as a percentage. It is the standard metric behind service level agreements (SLAs), infrastructure status pages, and reliability reporting. The formula is simple: divide the time the system was up by the total time in the period, then multiply by 100.

The formula

Uptime % = (Total time − Downtime) ÷ Total time × 100

Downtime and total time must be measured in the same units (both in minutes, or both in hours) and cover the same period. For example, a service that runs for a full 30-day month (43,200 minutes) but is unreachable for 43 minutes has uptime = (43,200 − 43) ÷ 43,200 × 100 = 99.9007%.

How this calculator works

Pick the time period the downtime was measured over — day, week, month, quarter, or year — then enter the downtime in hours and minutes. The calculator converts the period to total minutes using standard conventions (a 365-day year, a 7-day week, and an average month of 365/12 ≈ 30.44 days, which is the convention behind most published SLA tables), applies the uptime formula, and reports four things: the exact uptime percentage, the downtime you entered as a share of the period, the nearest standard SLA "nines" tier your result meets, and what that downtime rate would add up to if it held steady for a full year.

Reading the "nines"

Availability targets are commonly described by how many 9s appear in the percentage: 99% is "two nines," 99.9% is "three nines," 99.99% is "four nines," and so on. Each additional nine reduces the allowed downtime by roughly a factor of ten. Two nines allows about 3.65 days of downtime a year; three nines allows about 8.76 hours; four nines allows about 52.6 minutes; five nines allows about 5.3 minutes. Most consumer cloud services publish SLAs in the 99.9%–99.99% range; core network and payment infrastructure often targets 99.999% or better.

Why the period matters

The same number of downtime minutes means very different things depending on the period. Forty-five minutes of downtime is a rounding error across a year (99.991%) but a serious outage within a single day (96.875%). This calculator's annualized-downtime figure exists specifically to make short measurement windows comparable: it answers "if this rate continued all year, how much total downtime would that be?"

Frequently Asked Questions

What is the uptime formula?
Uptime % = (Total time − Downtime) ÷ Total time × 100. If a system runs for 720 hours (43,200 minutes) in a month and is down for 43 minutes, uptime = (43,200 − 43) ÷ 43,200 × 100 = 99.9007%.
What do the "nines" mean in an SLA?
They're shorthand for uptime tiers: two nines is 99% (about 3.65 days of downtime a year), three nines is 99.9% (about 8.76 hours a year), four nines is 99.99% (about 52.6 minutes a year), and five nines is 99.999% (about 5.26 minutes a year). Each extra nine cuts allowed downtime by roughly 10x.
How is monthly or weekly downtime converted to a yearly figure?
This calculator uses a 365-day year, a 7-day week, and an average month of 365/12 (about 30.44 days) — the same convention behind most published SLA reference tables — then scales your downtime percentage up to a full year so periods of different lengths can be compared on the same basis.
Does more decimal precision actually matter?
Yes. In a 43,200-minute month, the gap between 99.9% and 99.95% is about 21.6 minutes of downtime, and the gap between 99.99% and 99.999% is under 4 minutes. Small percentage-point differences represent very different real-world outage budgets, which is why SLAs are usually written to two or three decimal places.

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