Error Budget Calculator
Calculate remaining error budget based on your SLO target and current failure rate.
About Error Budget Calculator
An error budget is the amount of unreliability an SLO permits: budget = (1 − SLO) × time_period. For example, a 99.9% SLO over a 30-day period allows (1 − 0.999) × 30 × 24 × 60 = 43.2 minutes of downtime. Tracking consumption against this budget lets teams make data-driven decisions about when to slow down feature velocity in favor of reliability work.
Formula
errorBudget = (1 - sloTarget / 100) × timePeriodMinutes
- S
- SLO target percentage (e.g. 99.9)
- T
- Time period in minutes
- E
- Error budget in minutes of allowed downtime
Worked example
With the default values below, Error Budget Calculator returns Error Budget of 43.20. Change any input above and every figure here is recalculated in your browser.
Inputs used
- SLO Targetaccepts 0–100 %
- 99.9 %
- Time Periodaccepts 1–3,650 days
- 30 days
- Downtime So Faraccepts 0–1,000,000 minutes
- 0 minutes
Results
- Error Budget
- 43.20 minutes
- Error Budget
- 0.720 hours
- Remaining Budget
- 43.20 minutes
- Budget Consumed
- 0.0%
- Budget Exhausted
- false
Step by step
- 1Time period in minutes= 43,200 min
- 2Allowed downtime fraction: 1 − SLO= 0.001000
- 3Error budget: fraction × period= 43.20 min
- 4Remaining budget: budget − downtime so far= 43.20 min
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What's the error budget for 99.9% over 30 days?
(1 − 0.999) × 30 days × 1440 minutes/day = 43.2 minutes — this is the classic 'three nines' monthly budget cited in SRE literature.
What happens when the error budget is exhausted?
Most SRE practices freeze non-essential feature releases and prioritize reliability work until the service is back within its SLO for the measurement window.
Should error budget be measured in requests or time?
Time-based budgets suit availability SLOs; request-based budgets (bad requests / total requests) suit success-rate SLOs. Use whichever matches how your SLO is defined.
How does error budget relate to burn rate?
Burn rate is the speed at which you're consuming the error budget relative to the time elapsed in the period — a burn rate of 1x means you'll exhaust the budget exactly at period end; faster burn rates trigger earlier alerting.