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SLA uptime calculator — how much downtime does 99.9% allow?

Pick a target or type one. The calculator shows the downtime each 'nine' allows per day, week, month, quarter and year, and — given the downtime you have already had — how much of the budget remains.

Availability target

Allowed downtime at 99.9%

PeriodDowntime allowed
Day1m 26s
Week10m 5s
Month (30.44 d)43m 50s
Quarter2h 11m 29s
Year8h 45m 58s

Error budget

Budget43m 50s
Used0s
Remaining43m 50s
Achieved so far100.0000%
Monitor this continuously

Measure it instead of estimating it: SLA reports compute availability and remaining error budget per monitor or group, and can be scheduled to land before the review.

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How to read the result

  1. 199.9% allows about 43 minutes a month; 99.99% about 4 minutes. Each extra nine costs roughly ten times the engineering, so pick the one the contract actually needs.
  2. 2A month is taken as 30.44 days (365.25 / 12), which is how most SLA reports and PulseTrace's SLA reports compute it. Some contracts use the calendar month — check yours.
  3. 3Error budget is the allowed downtime minus the downtime already used. Once it is spent, the sensible policy is to stop shipping risky changes until the window rolls over.
  4. 4Availability in a contract is usually measured on the customer-facing endpoint from outside, not on internal uptime, so measure it that way.

Questions

Is 99.9% measured per month or per year?
Whatever the contract says — most SaaS SLAs are monthly, with credits per month. The calculator shows both so you can compare.
Does scheduled maintenance count?
Usually not, if the contract excludes announced maintenance windows. In PulseTrace a maintenance window stops incidents from opening for the covered monitors, so planned work is not recorded as an outage.

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