# Uptime SLA calculator: allowed downtime for 99.9%, 99.99% and more

> An uptime SLA states the share of time a service must be available. 99.9% uptime ("three nines") allows about 43 minutes 50 seconds of downtime per month, or 8 hours 46 minutes per year. 99.99% allows about 4 minutes 23 seconds per month, and 99.999% about 26 seconds. When services depend on each other, their availabilities multiply, so the combined SLA is lower than any single one.

- Interactive version: https://infikeytechnologies.com/tools/uptime-sla-calculator
- Type: free instant calculator
- Category: Cloud & infrastructure
- Last reviewed: 2026-10-05
- Publisher: Infikey Technologies (https://infikeytechnologies.com)

## Example result (default inputs)

| Input | Value |
| --- | --- |
| Uptime / SLA target | 99.9% |
| Services in the request path | 1 |

**Allowed downtime per month: 43m 50s.** 99.9% availability allows 43m 50s of downtime per month and 8h 45m 58s per year.

Three nines: a common target for business applications and the standard SLA of many single-region cloud services.

| Metric | Value |
| --- | --- |
| Per day | 1m 26s |
| Per week | 10m 5s |
| Per month | 43m 50s |
| Per quarter | 2h 11m 29s |
| Per year | 8h 45m 58s |

### Downtime per month at common SLA levels

| Item | Value | Detail |
| --- | --- | --- |
| 99% | 7h 18m 18s |  |
| 99.5% | 3h 39m 9s |  |
| Your SLA (99.9%) (selected) | 43m 50s |  |
| 99.95% | 21m 55s |  |
| 99.99% | 4m 23s |  |
| 99.999% | 26.3 seconds |  |


Open this result on the website: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.9&components=1

## Use from a link or API

Add these query parameters to https://infikeytechnologies.com/tools/uptime-sla-calculator (pre-filled page), https://infikeytechnologies.com/tools/uptime-sla-calculator.md (this plain-text page) or https://infikeytechnologies.com/api/tools/uptime-sla-calculator (JSON).

| Parameter | Meaning | Accepted values |
| --- | --- | --- |
| `uptime` | Uptime / SLA target | number from 50 to 99.99999 (%), default 99.9 |
| `components` | Services in the request path | number from 1 to 20, default 1 |

- 99%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99&components=1
- 99.9%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.9&components=1
- 99.95%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.95&components=1
- 99.99%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.99&components=1
- 99.999%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.999&components=1
- 3 services at 99.9%: https://infikeytechnologies.com/tools/uptime-sla-calculator?uptime=99.9&components=3

## How it is calculated

- **Allowed downtime**: period length × (1 − uptime % ÷ 100)
- **Combined availability (services in series)**: A₁ × A₂ × … × Aₙ
- **Year length used**: 365.25 days (month = year ÷ 12)

## Downtime allowed by common SLA levels

The table uses a 365.25-day year. Cloud providers and contracts sometimes measure per calendar month instead, which changes the monthly figure by a few seconds or minutes.

| Uptime | Per day | Per month | Per year |
| --- | --- | --- | --- |
| 99% | 14m 24s | 7h 18m 18s | 3d 15h 39m |
| 99.5% | 7m 12s | 3h 39m 9s | 1d 19h 49m |
| 99.9% | 1m 26s | 43m 50s | 8h 45m 58s |
| 99.95% | 43.2 seconds | 21m 55s | 4h 22m 59s |
| 99.99% | 8.6 seconds | 4m 23s | 52m 36s |
| 99.999% | 864 ms | 26.3 seconds | 5m 16s |

## Why chained services lower your real SLA

If a page needs a load balancer, an application server and a database, all three must be available at the same time. Their availabilities multiply: three services at 99.9% each give roughly 99.7% combined — about 2 hours 11 minutes of possible downtime a month instead of 44 minutes.

Redundancy works the other way. Two independent copies of a service, where either can serve traffic, fail together far less often, which is why production systems run across multiple availability zones.

## How to reach a higher uptime target

- Run at least two instances behind a load balancer, spread across availability zones.
- Use managed databases with automatic failover and tested backups.
- Deploy with zero-downtime releases (rolling or blue-green) so updates do not count against the SLA.
- Monitor from outside your network and alert on symptoms users feel, not only server metrics.
- Agree what counts as downtime: planned maintenance windows, partial outages and degraded performance are often excluded or measured separately.

## FAQ

### How much downtime is 99.9% uptime?

99.9% uptime allows about 1 minute 26 seconds of downtime per day, 43 minutes 50 seconds per month and 8 hours 46 minutes per year.

### How much downtime is 99.99% uptime?

99.99% ("four nines") allows about 8.6 seconds per day, 4 minutes 23 seconds per month and 52 minutes 36 seconds per year.

### What is the difference between 99.9% and 99.99% uptime?

Ten times less downtime: roughly 8.8 hours a year versus 53 minutes. Reaching four nines usually needs redundancy across zones, automatic failover and zero-downtime deployments.

### How do you calculate a composite SLA?

Multiply the availability of every service a request depends on. Two services at 99.9% give 0.999 × 0.999 = 99.8% combined.

### Does planned maintenance count as downtime?

It depends on the contract. Many SLAs exclude announced maintenance windows, so check the definition of downtime, the measurement period and how credits are calculated.

## Get expert help

Send these results to an Infikey Technologies specialist from the form on https://infikeytechnologies.com/tools/uptime-sla-calculator#estimate or via https://infikeytechnologies.com/contact.

More free calculators: https://infikeytechnologies.com/tools.md

## Disclaimer

This calculator is provided free for general information and planning only. Results are estimates based on the inputs you enter and the assumptions described on this page, reference data such as published prices may change, and actual costs and outcomes will differ. Nothing on this page is financial, legal, tax, investment or other professional advice. Infikey Technologies Private Limited, Infikey Technologies LLC and their directors, employees and affiliates make no warranty, express or implied, about the accuracy, completeness or suitability of this tool or its results, and accept no liability for any loss or damage, direct or indirect, arising from its use or from reliance on its results. Verify all figures independently and seek professional advice before making any decision. Use of this tool is at your own risk.