SLA Uptime and Error Budget Calculator

Pick a calculation, enter your target and period, and read the downtime or error budget.

Setup

Estimate downtime budget from target, outage, or SLA comparison

Choose what you know

Allowed downtime from uptime % Uptime % from actual downtime Compare vendor SLA vs internal target

Window

Fixed reporting windows: 28 or 30 days as selected; quarter = 91.3125 days; year = 365.25 days. These are duration estimates, not calendar months.

Common availability presets

Availability target (%)

Quick reliability budgeting. Enter a target once to see allowed downtime for each reporting window.

Actual downtime

Downtime unit

Use this mode after an incident, maintenance window, or outage review to see the achieved uptime for the selected period.

Vendor SLA (%)

Internal target (%)

Use this mode when a contract says one thing and your team operates to a tighter target. The result shows the gap in practical downtime terms.

Advanced / business impact

Cost per hour of downtime ($)

Optional business overlay. It does not change any uptime math, it only estimates what the selected availability level could mean in annual downtime cost.

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Reliability Workflow

Allowed downtime and target comparison Budget remaining and burn rate Incident timeline math

Run a scenario to derive allowed/achieved downtime and window-by-window operational impact.

Interpretation

Run a scenario to translate availability percentages or outage minutes into a budget the team can actually work with.

Outputs

Formula

After calculation, this panel shows the exact availability or downtime formula behind the result.

What this means

This summary calls out the main takeaway, the most relevant reporting windows, and any meaningful target gap between what is promised and what is expected.

Standard window breakdown

Calculate a scenario to see the allowed or achieved downtime across day, week, 28-day, 30-day, quarter, and year windows.

Uptime, downtime and error budgets

An uptime target such as 99.9% allows a fixed amount of downtime per month or year. An SLO error budget is the same idea applied to your own objective: subtract incident time to see how much budget is left and how fast you are burning it.

Some people, when confronted with a problem, think ‘I know, I’ll use regular expressions.’ Now they have two problems.
Jamie Zawinski