What does 99.9% uptime mean in downtime per year?

99.9% uptime allows approximately 8 hours 45 minutes and 36 seconds of downtime per year, or about 43 minutes and 49 seconds per month.

How many nines is 99.999%?

"Five nines" refers to 99.999% uptime, which allows only about 5 minutes and 15 seconds of downtime per year — roughly 26 seconds per month.

Does this tool use a 30-day or 31-day month?

The monthly calculation uses a standard 30-day month (2,592,000 seconds), which is the industry convention for SLA calculations.

What uptime percentage should I target?

Consumer websites often aim for 99.9% ("three nines"). E-commerce and SaaS platforms typically target 99.95% or 99.99%. Mission-critical systems (banking, healthcare) target 99.999% or higher.

Can I enter a custom uptime value like 99.95%?

Yes. Type any value between 0 and 100 into the input field. The tool computes the downtime budget for any arbitrary percentage.

SLA Uptime Calculator

Name: SLA Uptime Calculator
Availability: InStock
Author: Nham Vu

Enter an SLA uptime percentage and instantly see the maximum allowable downtime per day, month, and year.

Uptime Percentage

Enter a value between 0 and 100.

Common SLA tiers

Downtime Budget

Per Day

24 hours

Per Month

30-day month

Per Year

365-day year

Total downtime in seconds

/ day

/ month

/ year

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Summary

Enter an SLA uptime percentage and instantly see the maximum allowable downtime per day, month, and year.

How it works

Enter your target SLA uptime percentage (e.g. 99.9).
The tool computes the downtime percentage as 100 minus the uptime percentage.
It multiplies the downtime fraction against the seconds in a day, a 30-day month, and a 365-day year.
Results are displayed in the most readable unit — seconds, minutes, or hours — with full breakdowns.
Use the preset buttons to jump directly to common SLA tiers like 99%, 99.9%, 99.99%, or 99.999%.

Use cases

Verifying cloud provider SLAs before signing a contract.
Setting PagerDuty / OpsGenie alert budgets based on your uptime commitment.
Communicating to non-technical stakeholders how much downtime "four nines" actually allows.
Comparing uptime guarantees across multiple vendors.
Budgeting planned maintenance windows without breaching SLA.
Understanding the cost difference between 99.9% and 99.99% uptime for critical systems.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu