Uptime Calculator

Period	Allowed Downtime
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Uptime measures the proportion of time a service remains available to users. Service-level agreements (SLAs) convert that measure into contractual targets, often expressed as 99.9 % or higher. Error budgets represent the permissible downtime within those targets. Clearly understanding how these three metrics connect is essential to quantify reliability obligations.

The Uptime Calculator lets you enter a target availability percentage, operating period, and observed downtime. It instantly calculates allowed downtime, effective uptime, and remaining error budget, then signals whether the service stayed within its SLA target. Advanced options exclude planned maintenance and convert time units, giving SRE teams a sharper focus on incident-driven outages.

Use the results to prioritise remediation, negotiate realistic SLAs, or defend reliability reports during audits. For instance, spotting a 5 % error-budget burn early prompts preventive fixes before contractual penalties or user churn arise. By translating raw downtime into concrete financial and reputational stakes, the calculator aligns engineering efforts with stakeholder expectations and promotes data-driven service management.

Technical Details:

This section explains how each metric is derived from your inputs.

Customise the service-level target from 90 % to 99.999 % availability.
Select period length in seconds, minutes, hours, days, or weeks.
Record unplanned downtime in seconds, minutes, or hours.
Optionally exclude planned maintenance from outage totals.
View real-time progress bar reflecting error-budget burn.
Review allowed-downtime table for popular reference windows.
Instantly see a pass/fail alert showing SLA compliance status.

Metric	Formula	Example (99.9 %, 30 days)
Allowed Downtime (min)	Period min × (100 − Target) / 100	43.2
Effective Downtime (min)	Observed − Maintenance	10 − 3 = 7
Actual Uptime (%)	(1 − Effective / Period) × 100	99.983
Error-Budget Burn (%)	Effective / Allowed × 100	16.2

Calculations-and-Scoring:

The calculator applies four linked formulas to determine compliance.

Formula Breakdown

Step	Equation
1. Period Minutes	period_value × unit_factor
2. Allowed Downtime	Period × (100 − Target) / 100
3. Effective Downtime	Observed − Maintenance
4. Actual Uptime	(1 − Effective / Period) × 100

Worked Example

Given a 99.9 % target across 30 days (43 200 min) with 7 min unplanned downtime, allowed downtime equals 43.2 min. Actual uptime is 99.983 %, well within the SLA.

Interpretation

A burn percentage below 100 % indicates remaining error budget. Exceeding 100 % signals a breach requiring incident review.

Recommendations

Track burn trend daily. If usage exceeds 50 % mid-cycle, schedule preventive maintenance and investigate recurring root causes.

Step-by-Step Guide:

Follow these steps to compute uptime metrics.

Enter the desired SLA Target percentage.
Specify the Period Length value and choose its unit.
Input Downtime Experienced and select a unit.
Tip Toggle Advanced to add planned maintenance.
Verify figures; the card updates all metrics automatically.
Review the pass/fail alert and allowed-downtime table for context.

FAQ:

The answers below address common questions about uptime calculations.

Why does the calculator use minutes as the base unit?

Normalising all time values to minutes keeps rounding transparent and simplifies percentage calculations.

How accurate are fractional minutes?

Results display up to two decimal places, which balances readability with precision for most production scenarios.

Can I track multiple services simultaneously?

Open separate browser tabs for each service. Inputs persist per tab, allowing parallel assessments.

Does the tool account for time-zone differences?

Calculations rely solely on duration, not clock time. Therefore, time-zone differences do not affect results.

How is the progress bar colour decided?

The bar shows green when error-budget burn is under 100 % and switches to red once the limit is exceeded.