Error Budget & SLO Burn Rate
Calculate error budget consumption and burn rate from SLOs. Enter values for instant results with step-by-step formulas.
Formula
Burn Rate = (Budget Consumed %) / (Expected Consumption %)
Expected consumption is linear over the window (day 15 of 30 = 50%). Burn rate >1 means consuming faster than sustainable. Multi-window alerting catches both fast and slow burns.
Worked Examples
Example 1: Standard Web Service
Problem:SLO: 99.9%, 30-day window, 10M requests/month. Day 15: 5,000 failed requests, 30 min downtime.
Solution:Error Budget:\n100% - 99.9% = 0.1%\nRequests: 10M × 0.1% = 10,000 allowed failures\nTime: 30 days × 1440 min × 0.1% = 43.2 min allowed\n\nConsumed:\nRequests: 5,000 / 10,000 = 50%\nTime: 30 / 43.2 = 69.4%\n\nHigher of two: 69.4% consumed\n\nExpected (day 15 of 30): 50%\nBurn rate: 69.4% / 50% = 1.39x\n\nStatus: Elevated\nDays until exhausted: 30.6% / (69.4%/15) = 6.6 days
Result:1.39x burn rate (Elevated) | 69% consumed | 6.6 days until exhaustion
Example 2: Critical Payment API
Problem:SLO: 99.99%, 7-day window, 1M transactions. Day 3: 50 failures, 2 min downtime.
Solution:Error Budget:\n100% - 99.99% = 0.01%\nTransactions: 1M × 0.01% = 100 allowed\nTime: 7 × 1440 × 0.01% = 1.01 min allowed\n\nConsumed:\nTransactions: 50 / 100 = 50%\nTime: 2 / 1.01 = 198% (OVER BUDGET!)\n\nTime-based exhaustion: 198%\nBudget exhausted - already over!\n\nBurn rate: 198% / 42.9% = 4.6x\n\nStatus: Critical\nAction: Reliability freeze, incident review
Result:4.6x burn (Critical) | 198% consumed (OVER) | Budget exhausted
Example 3: Healthy Internal Service
Problem:SLO: 99.5%, 30-day window, 50M requests. Day 20: 100,000 failures, 60 min downtime.
Solution:Error Budget:\n100% - 99.5% = 0.5%\nRequests: 50M × 0.5% = 250,000 allowed\nTime: 30 × 1440 × 0.5% = 216 min allowed\n\nConsumed:\nRequests: 100K / 250K = 40%\nTime: 60 / 216 = 27.8%\n\nHigher: 40% consumed\n\nExpected (day 20): 66.7%\nBurn rate: 40% / 66.7% = 0.6x\n\nStatus: Excellent - Under budget!\n\nOpportunity: Can increase velocity,\ntake on riskier changes
Result:0.6x burn (Excellent) | 40% consumed | Room for velocity
Frequently Asked Questions
What is an SLO?
Service Level Objective is a target reliability level, e.g., '99.9% of requests succeed.' SLOs should be customer-focused, measurable, and achievable. They're internal targets, unlike SLAs which are contractual commitments.
What is an error budget?
Error budget is the allowed failure rate derived from SLO. For 99.9% SLO, error budget is 0.1% of requests or ~43 minutes/month of downtime. It quantifies acceptable unreliability and balances reliability with velocity.
What is burn rate?
Burn rate measures how fast you're consuming error budget relative to expected pace. 1.0 = on track, 2.0 = twice as fast (will exhaust in half the window). High burn rates trigger alerts and may halt deployments.
How do I set SLO targets?
Base on user expectations and business needs. Start with current baseline, aim for achievable improvement. 99.9% is common for most services, 99.99% for critical infrastructure. Higher isn't always better - over-engineering wastes resources.