# Uptime Percentage Calculator

> Turn measured downtime into an uptime percentage for the period.

Page: https://freecalculator.tech/tools/uptime-percentage-calculator
Last reviewed: 2026-09-16

## Formula

Uptime = (Measured time − Downtime) / Measured time, where Measured time = Period − Excluded time

- Uptime = (Measured time − Downtime) / Measured time, where Measured time = Period − Excluded time.
- Inputs used: Length of the period measured, Unavailable time in the period, Time excluded by agreement (optional).
- Edge handling: Length of the period measured is required.; Length of the period measured cannot be negative.; Length of the period measured must be no more than 1000000000000.; Unavailable time in the period is required.; Unavailable time in the period cannot be negative..

## Inputs

- Length of the period measured
- Unavailable time in the period
- Time excluded by agreement (optional)

## Worked example: 43 minutes down in a 30-day month

Measured uptime only. Whether it meets a target is a separate question.
1. Start with Length of the period measured: 720, Unavailable time in the period: 43, Time excluded by agreement (optional): 0.
2. Apply the method: Uptime = (Measured time − Downtime) / Measured time, where Measured time = Period − Excluded time.
3. Measured uptime only. Whether it meets a target is a separate question.

## Common questions

### Where does this formula come from?

Implementing SLOs — a service level objective is the share of good events among valid events (or of available time in the period); the error budget is the remainder that the objective permits. See the source link on this page.

### What kind of calculation is this?

Available time as a share of the time actually being measured. Check the formula, example, and limitations on this page before using the result for a real professional & industry decision.

### What are its limits?

Arithmetic over the figures entered — it cannot tell whether the underlying monitoring, incident records or change records are complete. A mean over a short period, or over few events, is a weak description of behaviour. A time-based figure can hide partial failures that a request-based objective would count.

### How do I use the Uptime Percentage Calculator?

Enter the required values for Length of the period measured, Unavailable time in the period, Time excluded by agreement (optional). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Uptime Percentage Calculator use?

Uptime = (Measured time − Downtime) / Measured time, where Measured time = Period − Excluded time The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone. Check the formula, example, and limitations on this page before using the result for a real professional & industry decision.

### Can the Uptime Percentage Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- Inputs outside the supported range are rejected rather than forced into a result.
- The result depends on the values you enter for this uptime percentage calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- Google — https://sre.google/workbook/implementing-slos/

## Cite this page

- APA: Free Calculator. (2026, September 16). Uptime Percentage Calculator. https://freecalculator.tech/tools/uptime-percentage-calculator
- MLA: "Uptime Percentage Calculator." Free Calculator, 16 Sept. 2026, https://freecalculator.tech/tools/uptime-percentage-calculator.
- Link: Uptime Percentage Calculator — Free Calculator, https://freecalculator.tech/tools/uptime-percentage-calculator