KBY Engineering Utilities

SLO and Error-Budget Suite

Calculate exact error budgets, observed SLI and versioned multiwindow burn-rate alert thresholds without floating-point loss.

Accuracy contract: All arithmetic uses integers and explicit rational rounding. The result is exact for the supplied SLI counts, SLO target and window; choosing the correct SLI remains the user's responsibility.

Inputs

Defined calculation contract

SLO targetDecimal percentage with up to six fractional digits. Must be below 100%.Compliance windowNumber of complete 24-hour days in the SLO window.Total valid eventsDenominator after applying the SLI's documented validity criteria.Bad eventsValid events that failed the SLI's good-event criteria.

Exact output

Calculation result

99.9%

SLO target

0.1%

Error budget

43m 12s

Allowed downtime

3000

Allowed bad events

1750

Remaining bad events

0.4167×

Burn rate

Observed event SLI

Total valid events: 3000000
Observed bad events: 1250
Actual SLI: 99.958333%
Budget consumed: 41.667%

Formulae

error budget = 100% − SLO
allowed bad events = floor(total valid events × error-budget fraction)
burn rate = observed bad-event ratio ÷ error-budget fraction

Raw time allowance: 2592000 ms across 2592000000 ms.

Multiwindow burn-rate plan

Exact thresholds derived from the supplied compliance window using the Google SRE 2%, 5% and 10% budget-spend policies.

Policy	Long / short	Spend	Burn	Error rate	Exhaustion
Fast page	1h / 5m	2%	14.4000×	1.440000%	2d 2h
Medium page	6h / 30m	5%	6.0000×	0.600000%	5d
Slow ticket	3d / 6h	10%	1.0000×	0.100000%	30d

Versioned sources

Google SRE: Service best practices and error budgets Google SRE Workbook: Implementing SLOs Google SRE Workbook: Alerting on SLOs

Deterministic v2026.07.3 — Principal · 3–8 min