--- title: "Uptime & Downtime Calculator - SLA % to Downtime | WebPixie" description: "Free uptime and SLA calculator. Turn an uptime percentage like 99.9% or 99.99% into allowed downtime per day, week, month, and year, plus reverse and cost modes." canonical: "https://webpixie.io/free-tools/uptime-calculator" source_path: "/free-tools/uptime-calculator" lang: "en" generated_by: "scripts/generate-md.mjs" --- 1. [Home](/index.md) 2. [Free Tools](/free-tools.md) 3. Uptime & Downtime Calculator # Uptime & Downtime Calculator Convert any uptime percentage into the downtime it allows per day, week, month, and year. Work backwards from observed downtime, or estimate the revenue an outage costs. ## What this calculator does Uptime is the share of time a service is reachable, written as a percentage. Downtime is the rest. This tool converts between the two so an abstract target like 99.9% becomes a concrete budget: the number of minutes or hours your service can be unavailable before it breaches that level. Enter an uptime percentage to see the allowed downtime per day, week, month, and year, or switch to the reverse mode to turn an observed outage back into a percentage. ## How downtime is calculated The formula is simple: downtime equals (1 minus uptime) multiplied by the length of the period. For 99.9% over a 30-day month, that is 0.001 times 2,592,000 seconds, which works out to roughly 43 minutes. Results here assume continuous 24/7 operation, with months fixed at 30 days and years at 365 days. Those fixed lengths keep shared links consistent, so the same URL always shows the same numbers. ## The nines, at a glance Availability targets are often described by their number of nines. Each extra nine cuts the allowed downtime by about a factor of ten, which is why the jump from 99.9% to 99.99% is much harder than it looks. The table below lists the common tiers and the downtime each one permits. | Uptime | Per day | Per week | Per month | Per year | | --- | --- | --- | --- | --- | | 99% | 14m 24s | 1h 40m 48s | 7h 12m | 3d 15h 36m | | 99.5% | 7m 12s | 50m 24s | 3h 36m | 1d 19h 48m | | 99.9% | 1m 26s | 10m 5s | 43m 12s | 8h 45m 36s | | 99.95% | 43s | 5m 2s | 21m 36s | 4h 22m 48s | | 99.99% | 9s | 1m | 4m 19s | 52m 34s | | 99.999% | 864ms | 6s | 26s | 5m 15s | ## Why downtime budgets matter - Setting an SLA target with a customer and needing to show the allowed downtime in plain minutes per month. - Tracking an error budget so engineering knows how much disruption a release can cause before the target is at risk. - Estimating the revenue impact of an outage to justify investment in redundancy or faster recovery. ## Turn these numbers into alerts A calculator tells you the budget. WebPixie watches your sites from multiple regions, measures real uptime against it, and notifies you as soon as a check fails. [See Uptime Monitoring](/features/uptime-monitoring.md) ### Frequently asked questions Common questions about uptime, downtime, and SLAs. ### How much downtime does 99.9% uptime allow? **99.9% uptime** (three nines) allows about **43 minutes** of downtime per 30-day month. Broken down by period: - **per day:** about 1 minute 26 seconds - **per week:** about 10 minutes - **per month:** about 43 minutes - **per year:** about 8 hours 46 minutes The math is the length of the period multiplied by **0.1%**. Three nines is a common target for standard business services, while revenue-critical systems often aim higher. To see whether you stay within that budget, WebPixie [uptime monitoring](/features/uptime-monitoring.md) measures real availability from several regions. ### What is the difference between 99.9% and 99.99% uptime? **99.99% allows about ten times less downtime than 99.9%**, cutting the monthly budget from roughly **43 minutes to about 4 minutes**. Each additional nine reduces permitted downtime by an order of magnitude, which is why every step up is harder and usually more expensive. Four nines, at about 4 minutes a month, leaves little room for a slow deploy or a brief network blip, so it generally requires **redundancy and automated failover**. The calculator above lets you enter each percentage and compare the budgets side by side. You can see what monitoring each WebPixie plan includes on the [pricing page](/pricing.md). ### What is a good uptime percentage? A good target depends on the service, but **99.9% is a widely used baseline** for business sites and applications. Typical tiers: - **99% to 99.5%** for internal tools - **99.9%** for most business services - **99.95% to 99.99%** for ecommerce, payment, and revenue-critical systems Higher is not always better, because each extra nine demands more redundancy and faster detection for a smaller reduction in downtime. Pick the lowest target that meets user expectations, express it as a downtime budget above, then track it. WebPixie [uptime monitoring](/features/uptime-monitoring.md) records real availability so you can confirm the target is realistic. ### What is an SLA and how does downtime relate to it? An **SLA** (service level agreement) is a formal commitment to a minimum availability, usually written as an uptime percentage such as **99.95%**. The allowed downtime is the **error budget** the SLA permits before it is breached; a 99.95% SLA, for example, allows about **22 minutes per month**. Teams use the budget to decide how much risk a release or maintenance window can take. The calculator above converts any SLA figure into plain minutes for the day, week, month, and year. To prove you met an SLA you need a record of real availability, which WebPixie [uptime monitoring](/features/uptime-monitoring.md) and [incident management](/features/incident-management.md) provide. ### Does uptime include scheduled maintenance? **It depends on the SLA, and the distinction matters.** Many SLAs exclude scheduled maintenance announced in advance, counting only **unplanned** outages, while others count all unavailability. When you set a target, decide which definition you use, because excluding maintenance makes a given percentage easier to meet. The calculator above treats the period as continuous **24/7** time, so the downtime it shows is the total budget before any exclusions you apply. If your SLA excludes maintenance, subtract those windows from the measured downtime. WebPixie [uptime monitoring](/features/uptime-monitoring.md) calculates availability with the industry-standard method that excludes unmonitored periods. ### How do I estimate the cost of downtime? Estimate the cost of downtime by multiplying the **expected downtime** by your **revenue or cost per hour**. If your site earns `$2,000` an hour and your target allows 4 hours of downtime a year, the modeled exposure is about `$8,000`. The calculator above includes a **cost mode** where you enter an hourly figure and see the projected loss for each period, which helps justify spending on redundancy or faster recovery. The estimate is only as good as the hourly figure, so use a realistic blended number that includes lost sales and recovery effort. Pairing the estimate with [uptime monitoring](/features/uptime-monitoring.md) gives you both the budget and the live measurement. ### What is five nines (99.999%) uptime? **Five nines means 99.999% availability**, which allows only about **26 seconds** of downtime per month, or roughly **5 minutes 15 seconds per year**. It is the standard often quoted for telecom and critical infrastructure. Reaching it is demanding because almost no manual response is fast enough, so it requires **redundant systems, automated failover, and detection within seconds**. For most websites five nines is more than the business needs, and the cost outweighs the benefit. The nines table in the calculator above lists five nines next to the lower tiers so you can compare the budgets directly. Fast detection through [uptime monitoring](/features/uptime-monitoring.md) is a prerequisite for any high tier. ### How is uptime measured in practice? Uptime percentage is **available time divided by total time, times 100**, but how you measure the available time matters. Monitoring tools check a site at a fixed interval from one or more locations, record each check as up or down, then add up the down periods. A **shorter interval** and **several locations** give a more accurate figure and catch regional outages. The calculator above also has a **reverse mode**: enter an observed outage and it returns the resulting percentage, which is handy after an incident. WebPixie [uptime monitoring](/features/uptime-monitoring.md) checks from several regions and retries before counting a failure, so a single failed check does not distort the percentage. Checking a specific site? Look up its registration and expiry with the [Domain Lookup tool](/free-tools/domain-lookup.md) while you are here. ## Source Attribution This file is automatically generated by WebPixie AI and summarizes publicly available content from WebPixie pages. Authoritative details should always be verified from the original URLs.