# Error Budget Calculator

> See how much of your objective's error budget is left, by events or by time.

Page: https://freecalculator.tech/tools/error-budget-calculator
Last reviewed: 2026-09-16

## Formula

Error budget = Valid events × (1 − SLO); Remaining = Error budget − Bad events. By time: Error budget = Period × (1 − SLO); Remaining = Error budget − Downtime

- Error budget = Valid events × (1 − SLO); Remaining = Error budget − Bad events. By time: Error budget = Period × (1 − SLO); Remaining = Error budget − Downtime.
- Inputs used: How is your objective measured?, Service level objective, Valid requests in the period, Requests that failed the objective, Length of the period, Unavailable time so far.
- Edge handling: Service level objective is required.; Service level objective cannot be negative.; Service level objective must be no more than 100.; Valid requests in the period is required.; Valid requests in the period cannot be negative..

## Inputs

- How is your objective measured?
- Service level objective
- Valid requests in the period
- Requests that failed the objective
- Length of the period
- Unavailable time so far

## Worked example: A 99.9% objective over 20 million requests

The budget is what the objective you entered permits — not a recommended allowance.
1. Start with How is your objective measured?: events, Service level objective: 99.9, Valid requests in the period: 20000000, Requests that failed the objective: 9000, Length of the period: 720, Unavailable time so far: 20.
2. Apply the method: Error budget = Valid events × (1 − SLO); Remaining = Error budget − Bad events. By time: Error budget = Period × (1 − SLO); Remaining = Error budget − Downtime.
3. The budget is what the objective you entered permits — not a recommended allowance.

## 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?

The failures an objective permits over a period, less the failures recorded so far. 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 budget for a period says nothing about how quickly it is being spent within that period.

### How do I use the Error Budget Calculator?

Enter the required values for How is your objective measured?, Service level objective, Valid requests in the period, Requests that failed the objective, Length of the period, and the other fields shown. 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 Error Budget Calculator use?

Error budget = Valid events × (1 − SLO); Remaining = Error budget − Bad events. By time: Error budget = Period × (1 − SLO); Remaining = Error budget − Downtime 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.

### Can the Error Budget 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 error budget 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). Error Budget Calculator. https://freecalculator.tech/tools/error-budget-calculator
- MLA: "Error Budget Calculator." Free Calculator, 16 Sept. 2026, https://freecalculator.tech/tools/error-budget-calculator.
- Link: Error Budget Calculator — Free Calculator, https://freecalculator.tech/tools/error-budget-calculator