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Uptime Calculator

Calculate the maximum allowed downtime for any SLA percentage — per year, month, week and day.

99.9%

Quick Reference

Common SLA tiers
SLA Name Per Year Per Month Per Week Per Day
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What is SLA?

Service Level Agreement defines the guaranteed uptime percentage for a service over a period.

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Nines

"Five nines" (99.999%) allows only ~5.26 minutes of downtime per year — the gold standard for critical infrastructure.

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Planned maintenance

Maintenance windows count against your SLA unless explicitly excluded in the agreement.

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Calculation

Downtime = (1 − uptime%) × period. E.g. 99.9% over 1 year = 0.001 × 8760h = 8.76h max downtime.

Uptime Calculator — SLA Downtime & Nines Explained

SLA (Service Level Agreement) uptime percentages determine how much downtime is acceptable per year. "Five nines" (99.999%) allows only 5.26 minutes of downtime per year. Use our calculator to understand what your SLA commitment actually means in practice.

What does 99.9% uptime mean?

99.9% uptime (three nines) allows 8.76 hours of downtime per year, ~43.8 minutes per month. For most websites and SaaS applications, this is considered acceptable.

What is "five nines" (99.999%)?

99.999% uptime allows only 5.26 minutes of downtime per year (~26 seconds per month). This is the standard for critical infrastructure, financial systems, and emergency services.

Does planned maintenance count against SLA?

It depends on the SLA agreement. Some SLAs exclude scheduled maintenance windows. Others count all downtime regardless of cause. Always read your provider's SLA definition carefully.

How do I improve my uptime?

Key strategies: redundant servers (N+1 or N+2), geographic load balancing, automatic failover, health checks every 30 seconds, CDN for static assets, and database read replicas. Target SLA determines architecture complexity.

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