{
    "name": "Availability Percentage Calculator",
    "url": "https://calculators.geekmidst.com/calculators/availability-percentage-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/availability-percentage-calculator.md",
    "category": "IT, networking & security",
    "description": "Measure availability from actual downtime over a period, or from MTBF and MTTR, and see the number of nines and the downtime that rate implies per year.",
    "summary": "Availability is the share of time a service was usable: uptime divided by the time measured. Enter observed downtime, or mean time between failures and mean time to recover, to get the percentage and its “nines”.",
    "also_called": [
        "Uptime percentage calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "mode",
            "label": "Calculate from",
            "type": "segmented",
            "default": "downtime",
            "options": {
                "downtime": "Measured downtime",
                "mtbf": "MTBF and MTTR"
            }
        },
        {
            "name": "period_days",
            "label": "Measurement period",
            "type": "number",
            "default": "30",
            "unit": "days",
            "shown_when": {
                "mode": "downtime"
            }
        },
        {
            "name": "downtime_min",
            "label": "Unplanned downtime",
            "type": "number",
            "default": "43.2",
            "unit": "min",
            "shown_when": {
                "mode": "downtime"
            }
        },
        {
            "name": "excluded_min",
            "label": "Excluded planned maintenance",
            "type": "number",
            "default": "",
            "unit": "min",
            "optional": true,
            "shown_when": {
                "mode": "downtime"
            }
        },
        {
            "name": "mtbf",
            "label": "Mean time between failures",
            "type": "number",
            "default": "999",
            "unit": "h",
            "shown_when": {
                "mode": "mtbf"
            }
        },
        {
            "name": "mttr",
            "label": "Mean time to recover",
            "type": "number",
            "default": "1",
            "unit": "h",
            "shown_when": {
                "mode": "mtbf"
            }
        }
    ],
    "outputs": [
        {
            "key": "availability",
            "label": "Availability",
            "format": "percent"
        },
        {
            "key": "nines",
            "label": "Number of nines",
            "format": "text"
        },
        {
            "key": "unavailability",
            "label": "Unavailability",
            "format": "percent"
        },
        {
            "key": "downtime_year_min",
            "label": "Downtime per year at this rate",
            "format": "number"
        },
        {
            "key": "downtime_month_min",
            "label": "Downtime per 30-day month",
            "format": "number"
        },
        {
            "key": "downtime_week_min",
            "label": "Downtime per week",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Availability = (Measured time − Downtime) ÷ Measured time, where Measured time = Period − Excluded maintenance;  or Availability = MTBF ÷ (MTBF + MTTR);  Nines = −log₁₀(1 − Availability)",
        "variables": {
            "Downtime": "unplanned time the service was unusable",
            "MTBF": "mean time between failures",
            "MTTR": "mean time to recover",
            "Year": "365.25 days (525,960 minutes)"
        }
    },
    "worked_example": {
        "inputs": {
            "mode": "downtime",
            "period_days": "30",
            "downtime_min": "43.2",
            "excluded_min": "",
            "mtbf": "999",
            "mttr": "1"
        },
        "steps": [
            "Measured time = 30 × 1,440 = 43,200 min.",
            "Availability = (43,200 − 43.2) ÷ 43,200 = 99.9%.",
            "At that rate a year has 0.1% × 525,960 = 525.96 min (about 8.77 h) of downtime."
        ],
        "result": "43.2 minutes of downtime in 30 days is 99.9% availability, or three nines."
    },
    "interpretation": "Compare the result with your SLA or SLO. Each extra nine cuts allowed downtime by a factor of ten, which usually needs a step change in architecture, not just faster fixes.",
    "assumptions": [
        "Downtime is total: partial outages count fully unless you weight them yourself."
    ],
    "limitations": [
        "The MTBF/MTTR form is a steady-state average; short periods with few incidents can differ a lot from it."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "How is this different from an SLA downtime calculator?",
            "answer": "An SLA downtime calculator starts from a target such as 99.9% and tells you how much downtime it allows. This page starts from what actually happened and gives the availability achieved."
        },
        {
            "question": "Does planned maintenance count as downtime?",
            "answer": "It depends on your SLA. Many exclude announced maintenance; enter it in the excluded field to remove it from the measured period."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Mean Time to Recover (MTTR) Calculator",
            "url": "https://calculators.geekmidst.com/calculators/incident-mean-time-to-recover-calculator"
        },
        {
            "name": "Percentage Calculator",
            "url": "https://calculators.geekmidst.com/calculators/percentage-calculator"
        },
        {
            "name": "Time Duration Calculator",
            "url": "https://calculators.geekmidst.com/calculators/time-duration-calculator"
        },
        {
            "name": "Uptime SLA Downtime Calculator",
            "url": "https://calculators.geekmidst.com/calculators/website-uptime-sla-downtime-calculator"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}