Uptime SLA Downtime & Credit Calculator
Calculate exact allowed downtime for 99% to 99.999% SLA availability targets across years, months, weeks, and days, and estimate revenue impact.
1m 26s
10m 4s
43m 49s
8h 45m 57s
Outage Financial Loss & SLA Breach Estimator
$13.69
Based on continuous revenue rate during the 60-minute incident. Does not include brand reputation damage or PPC ad waste.
Standard Availability Tier Reference Matrix
| SLA Tier | Per Day | Per Month | Per Year |
|---|---|---|---|
| 99.0% (Two Nines) | 14m 24s | 7h 18m 17s | 3d 15h 39m |
| 99.5% | 7m 12s | 3h 39m 08s | 1d 19h 49m |
| 99.9% (Three Nines - Industry Standard) | 1m 26s | 43m 49s | 8h 45m 57s |
| 99.95% (High Availability Cloud) | 43.2s | 21m 54s | 4h 22m 58s |
| 99.99% (Four Nines - Enterprise) | 8.6s | 4m 22s | 52m 35s |
| 99.999% (Five Nines - Mission Critical) | 0.86s | 26.3s | 5m 15s |
Understanding SLA Availability Tiers
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1. Why the industry talks in "nines"
"Three nines," "four nines," and "five nines" refer to the count of consecutive 9s in the percentage (99.9%, 99.99%, 99.999%) — shorthand that became standard because the absolute downtime allowance shrinks dramatically with each additional nine. The jump from three to four nines cuts allowed annual downtime from about 8.7 hours to about 52 minutes; four to five nines cuts it further to about 5 minutes. Each additional nine typically requires an order of magnitude more engineering investment to achieve reliably.
2. What infrastructure is needed for each tier
99.9% is achievable with a single well-maintained server and basic monitoring — most standard shared and managed WordPress hosting targets this tier. 99.95-99.99% typically requires redundant infrastructure within a region (load-balanced servers, automatic failover, redundant database replicas) so a single server failure doesn't cause an outage. 99.999% generally requires multi-region active-active architecture, where traffic can be rerouted to an entirely different geographic region within seconds of a regional failure — the kind of infrastructure large cloud platforms and financial systems invest in.
3. Reading the fine print in hosting SLA contracts
Pay close attention to exclusions: most SLAs don't count scheduled maintenance (if pre-announced within a specified window), issues caused by your own application code or misconfiguration, force majeure events, or attacks like DDoS that overwhelm capacity beyond what was provisioned. Also check the credit structure — a typical SLA credit is a percentage discount on that billing period's fees, which rarely comes close to compensating for actual business impact of an outage; the credit is a goodwill gesture and accountability mechanism, not real insurance.
4. How the measurement window affects your protection
Some SLAs measure availability monthly, others quarterly or annually — this matters more than it first appears. A monthly-measured 99.9% SLA gives you a fresh downtime allowance every month; an annual-measured one means a bad month can be "made up for" by good months elsewhere in the year, potentially masking a real reliability problem for months before it becomes visible in the aggregate figure. When comparing providers, check which measurement window applies — a shorter window generally gives you more responsive accountability.
5. Practical guidance for choosing a tier
For most WordPress business sites and small-to-medium e-commerce stores, 99.9% from a reputable managed host is a reasonable target — the incremental cost of 99.99%+ infrastructure rarely pays for itself unless your revenue-per-minute (calculated above) is high enough that even the marginal reduction in downtime meaningfully moves the needle. For mission-critical platforms — payment processing, SaaS products with enterprise customers holding their own SLA commitments to you — the higher tiers become a genuine business requirement rather than a nice-to-have.
Frequently Asked Questions
What is a Service Level Agreement (SLA) uptime guarantee?
An SLA is a formal commitment by a hosting provider, CDN, or cloud platform defining the minimum percentage of time their infrastructure will be operational and reachable. Common commitments range from 99.9% ("Three Nines") to 99.99% ("Four Nines").
What is the difference between 99.9% and 99.99% availability?
99.9% availability allows approximately 43 minutes and 49 seconds of downtime per month (8.7 hours per year). 99.99% allows only 4 minutes and 22 seconds of downtime per month (52 minutes per year) — requiring multi-region redundancy and automatic failover.
What are SLA Service Credits in hosting agreements?
If a hosting provider fails to meet its guaranteed uptime target during a billing cycle, most contracts allow customers to claim service credits (typically 10% to 50% refund of that month's hosting fee) upon written request.
Does scheduled maintenance count against an SLA?
Most standard commercial hosting SLAs explicitly exclude scheduled, pre-announced maintenance windows and client application code errors from downtime calculations.
Is a higher-nines SLA always worth paying more for?
Not automatically — it depends on your actual traffic pattern and revenue sensitivity. A 99.99% SLA over 99.9% only saves about 39 minutes of potential downtime per year, which matters enormously for a high-transaction-volume platform but may not justify the typically much higher cost of the redundant, multi-region infrastructure required to achieve it for a lower-traffic site. Calculate your own revenue-per-minute (using the estimator above) and compare it against the price difference between SLA tiers to make an informed decision.
How do I actually verify my hosting provider is meeting their SLA?
Use independent third-party uptime monitoring (a service that pings your site from external locations at regular intervals) rather than relying solely on your provider's own reported uptime — providers measuring their own uptime have an inherent incentive alignment issue. Keep your own incident log with timestamps of any observed downtime, since most SLA credit claims require you to provide evidence, not just assert that an outage occurred.
Why do the downtime figures use 30.4375 days per month and 365.25 days per year?
These are the average month length (365.25 ÷ 12) and average year length (accounting for leap years occurring roughly every 4 years) — using precise averages rather than a flat "30 days" or "365 days" keeps the calculated allowances consistent with how uptime percentages are actually computed over long time horizons in real SLA contracts, which typically measure availability over rolling 12-month periods.