---
title: "Uptime Calculator: SLA Downtime for 99.9%, 99.99% & More"
description: "Free uptime and SLA calculator. See allowed downtime per day, week, month, quarter and year for any uptime percentage, or turn downtime into an uptime %."
url: https://statusentry.com/tools/uptime-calculator
updated: 2026-10-20
---

Free tool

# Uptime & SLA calculator

Enter an uptime percentage to see how much downtime it allows, or enter downtime to get your uptime %. Free, no sign-up.

## Allowed downtime for an uptime target

Uptime %

Per day

1m 26s

Per week

10m 5s

Per month

43m 50s

Per quarter

2h 11m 29s

Per year

8h 45m 58s

## Uptime % from downtime

Downtime (minutes)

Period

Uptime

99.931%

SLA reference

## Downtime allowed by common SLA levels

| Uptime | Per day | Per week | Per month | Per quarter | Per year |
| --- | --- | --- | --- | --- | --- |
| 99% | 14m 24s | 1h 40m 48s | 7h 18m 18s | 21h 54m 54s | 3d 15h 39m 36s |
| 99.5% | 7m 12s | 50m 24s | 3h 39m 9s | 10h 57m 27s | 1d 19h 49m 48s |
| 99.9% | 1m 26s | 10m 5s | 43m 50s | 2h 11m 29s | 8h 45m 58s |
| 99.95% | 43s | 5m 2s | 21m 55s | 1h 5m 45s | 4h 22m 59s |
| 99.99% | 9s | 1m | 4m 23s | 13m 9s | 52m 36s |
| 99.999% | 1s | 6s | 26s | 1m 19s | 5m 16s |

Based on a 365.25-day year; a month is one twelfth of a year.

Guide

## How to use uptime targets

- **Pick an SLA you can keep.** 99.9% leaves about 43 minutes a month for incidents and maintenance; 99.99% leaves about 4 minutes.
- **Decide whether scheduled maintenance counts.** Many SLAs exclude announced maintenance windows, so [announce maintenance properly](https://statusentry.com/blog/how-to-announce-scheduled-maintenance).
- **Measure it.** Endpoint monitoring tells you when a service is down and for how long.
- **Show it.** A public status page with uptime history builds trust and cuts “is it down?” tickets. See the [status page glossary](https://statusentry.com/glossary) for SLA, SLO and SLI.

## Uptime calculator FAQ

**How much downtime is 99.9% uptime?**

99.9% uptime (“three nines”) allows about 1m 26s of downtime per day, 43m 50s per month and 8h 45m 58s per year.

**How much downtime is 99.99% uptime?**

99.99% uptime (“four nines”) allows about 9s per day, 4m 23s per month and 52m 36s per year.

**How do you calculate uptime percentage?**

Uptime % = (total time − downtime) ÷ total time × 100. For example, 30 minutes of downtime in a 30-day month is (43,200 − 30) ÷ 43,200 × 100 = 99.93%.

**What is the difference between an SLA, SLO and SLI?**

An SLI is what you measure (for example, successful requests). An SLO is your internal target for it (99.95%). An SLA is the promise you make to customers (99.9%), usually with credits if you miss it.

**How should I show uptime to customers?**

A public status page with an uptime history per service shows customers your real availability and where to find updates during an incident.

## Track and show your uptime.

Statusentry gives you a public status page with uptime history, and endpoint monitoring from $9.99/month. Start free.

[Create your status page](https://app.statusentry.com/signup) [More free tools](https://statusentry.com/resources)