FREE · NETWORK & IT INFRASTRUCTURE
Uptime & SLA Calculator.
Convert an availability percentage into allowed downtime, and estimate the availability of a system from its components and redundancy.
- Allowed downtime per month
- 43.8 min
- Allowed downtime per year
- 8.8 h
- Estimated system availability
- 99.8875 %
- Expected downtime per year
- 9.9 h
- Meets the target
- No
Components in series (each line may be redundant)
| Component | Each | Copies | Combined |
|---|---|---|---|
| Internet link | 99.5 % | 2 | 99.9975 % |
| Firewall | 99.95 % | 2 | 99.99997 % |
| Load balancer | 99.99 % | 1 | 99.99 % |
| Web servers | 99.5 % | 3 | 99.99999 % |
| Database | 99.9 % | 1 | 99.9 % |
Downtime budget
| Period | Allowed downtime |
|---|---|
| Per day | 86.4 s |
| Per week | 10.1 min |
| Per month (30.44 days) | 43.8 min |
| Per quarter | 2.2 h |
| Per year | 8.8 h |
Common targets
| Availability | Per day | Per week | Per month (30.44 days) | Per quarter | Per year |
|---|---|---|---|---|---|
| 99 % | 14.4 min | 100.8 min | 7.3 h | 21.9 h | 3.7 days |
| 99.5 % | 7.2 min | 50.4 min | 3.7 h | 11 h | 43.8 h |
| 99.9 % | 86.4 s | 10.1 min | 43.8 min | 2.2 h | 8.8 h |
| 99.95 % | 43.2 s | 5 min | 21.9 min | 65.8 min | 4.4 h |
| 99.99 % | 8.6 s | 60.5 s | 4.4 min | 13.2 min | 52.6 min |
| 99.999 % | 864 ms | 6 s | 26.3 s | 78.9 s | 5.3 min |
- Components in series multiply their availabilities; n redundant copies give 1 − (1 − A)ⁿ, assuming independent failures and instant failover — real systems share power, software and people, so treat the result as an upper bound.
- Check how your contract measures availability: scheduled maintenance, measurement interval and partial outages are often excluded.
How to use Uptime & SLA Calculator
Enter the target availability, then optionally list components with their availability and number of redundant copies, or an MTBF and MTTR.
How it works
Downtime = period × (1 − availability). Components in series multiply; n redundant copies give 1 − (1 − A)ⁿ; MTBF ÷ (MTBF + MTTR) gives a unit’s availability.
Example
99.9 % allows 8.8 hours of downtime a year or 43.8 minutes a month; two 99.5 % links in parallel reach 99.9975 %.
Questions about Uptime & SLA Calculator
Is Uptime & SLA Calculator free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
Assumes independent failures and instant failover; real systems share risks, so the composite figure is an upper bound. Everything is calculated in your browser; nothing is sent or probed on the network. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.