Uptime SLA Error Budget Calculator

Converts an uptime target like 99.9 percent into allowed minutes of downtime, then checks whether your real incident pattern fits inside that budget.

Your estimate

Allowed downtime for the period...

Projected downtime for the period...

Projected uptime...

Budget status...

Estimates only. Assumptions are listed below, and you can change every input.

Uptime percentages hide the number that actually matters: how many minutes you are allowed to be down. A 99.9 percent monthly SLA sounds strict until you realize it permits about 43 minutes of downtime, and 99.99 percent permits barely four. Teams sign SLAs without knowing whether their usual incidents, detection delays and fix times can possibly fit inside that window.

This calculator does two things. First it turns your target percentage into an allowed downtime budget for the period you choose. Then it estimates your projected downtime from the incidents you typically see per month, the time it takes to notice each one and the time it takes to resolve it. Comparing the two tells you honestly whether you are within budget, and by how much, before a customer does the math for you.

How to use this tool

Enter the uptime percentage from your SLA or objective and choose the period it is measured over.
Enter how many outages you typically see per month, plus the average minutes to detect and to resolve each one.
Compare allowed downtime with projected downtime; if you are over budget, reducing detection time is usually the cheapest lever to pull.

What the math assumes

A month is treated as 30 days, a quarter as 91 days and a year as 365 days, so allowed minutes are approximate for calendar months of other lengths.
Every incident is assumed to be a full outage; partial degradation is counted the same as complete downtime.
Incidents per month are scaled linearly to the chosen period, so two per month becomes 24 per year.
Detection and resolution times are averages; a single unusually long incident can blow a monthly budget even when the average looks fine.
Planned maintenance is counted as downtime unless your SLA excludes it, in which case leave it out of your incident count.

Frequently asked questions

How many minutes of downtime does 99.9 percent allow per month?

About 43 minutes on a 30 day month. Per year it is roughly 8 hours and 46 minutes. Moving to 99.95 percent halves that, and 99.99 percent allows only about 4 minutes a month.

Does the calculator measure my actual uptime?

No. It projects downtime from the incident pattern you describe. Your monitoring history is the source of truth for actual uptime; use it to fill in realistic incident counts and durations rather than best-case numbers.

What is the fastest way to get back inside the budget?

Time to detect is usually the easiest number to shrink, because it depends on your check interval and alerting rather than on how hard the bug is. Cutting detection from 10 minutes to 2 minutes on two incidents a month saves 16 minutes of budget without changing anything about how you fix outages.

Link to this toolhttps://pingcrumb.com/tools/uptime-sla-error-budget-calculator/

Free for readers and publishers alike. If you cite the result in an article, a link to this page helps others find it.

More free tools from PingCrumb

Website Downtime Cost Calculator: Estimates what a single outage costs a SaaS or online business in lost revenue, response labor and credits, so you can put a real number on uptime.
Uptime Check Interval Detection Time Calculator: Shows how long an outage can go unnoticed at a given check interval and confirmation setting, and how many monitoring requests that setup sends per month.

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