How to Calculate Downtime from Uptime: Formula, Steps & Examples
Learn how to calculate Downtime from Uptime — the formula explained step by step, with worked examples and a free calculator to check your answer.
Downtime from Uptime Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Allowed downtime
0.720
- In minutes
- 43.2
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Downtime from Uptime Calculator
The Downtime from Uptime Calculator works out your allowed downtime, along with 1 related figure in an instant. Enter target uptime and period and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the target uptime.
- Enter the period.
- Read off your allowed downtime, together with in minutes — the calculator updates automatically, with no button to press.
Formula
The Downtime from Uptime Calculator uses the formula:
Allowed downtime = (1 - Target uptime ÷ 100) × Period
Worked example
For example, with target uptime of 99.9% and period of 720 hours, the allowed downtime is 0.720.
| Target uptime | 99.9% |
|---|---|
| Period | 720 hours |
| Allowed downtime | 0.720 |
|---|---|
| In minutes | 43.2 |
Results are estimates for educational use, not professional advice.
Frequently asked questions
Multiply the period by (1 − uptime). At 99.9% over 720 hours, that is about 0.72 hours, or 43 minutes.
About 52.6 minutes of downtime over a 365-day year.
Service-level agreements promise availability, and the allowed downtime sets the maintenance and failure budget.
It depends on the agreement; some exclude scheduled maintenance from the downtime budget.
The Downtime from Uptime Calculator uses the formula: Allowed downtime = (1 - Target uptime ÷ 100) × Period. For example, with target uptime of 99.9% and period of 720 hours, the allowed downtime is 0.720.
Enter the target uptime. Enter the period. Read off your allowed downtime, together with in minutes — the calculator updates automatically, with no button to press.