Example 1
- SLO 99.9
- 30 days
- used 0
525.60 min/year
What error budget at SLO 99.9? 525.60 min/year. A 525600 model, not Prometheus.
Error Budget Calculator (SRE)
Type SLO, period days, and used minutes. 99.9 gives 525.60 min/year. 99.99 gives 52.56 min/year. 99.5 gives 2628 min/year. A year model, not a live SLO.
This is 525600 × (100−SLO)/100 minutes per year. Not a Prometheus metric. Cadence sits on deploy frequency.
Results
Enter data and click Calculate.
How it works
Error Budget Calculator (SRE) in this calculator times year minutes from an SLO. 99.9 gives 525.60 min/year. 99.99 gives 52.56 min/year. 99.5 gives 2628 min/year. The formula is 525600 × (100 − SLO) / 100. The calculator does not read Prometheus.
Field slo-pct is the percent. Fields error-budget-period-days and error-budget-used-min are in the fill, but extras keep the year budget. 525600 × 0.001 = 525.60. 525600 × 0.0001 = 52.56. 525600 × 0.005 = 2628. Used 10 or 60 does not change that primary.
525.60 min/year does not come from Grafana. 52.56 is not an SLI from a probe. 2628 does not know an incident. You type the SLO. This is not a live SLO.
Deploy frequency next door divides a count by days. MTTR times repair. Here 99.9 stays 525.60 min/year, the year model alone.
Type 99.9, 30, and 0, then Calculate. The year result is 525.60 min/year. 99.99 with 10 used still 52.56 min/year on the extras card.
99.9 gives 525.60 min/year. 99.99 gives 52.56 min/year. 99.5 gives 2628 min/year. Another SLO changes 525.60.
Formula
minutes / year = 525600 × (100 − SLO) / 100. The result is the year, not remainder after used.
How to use
- Type SLO 99.9, period 30, and used 0.
- Click Calculate. The year budget is 525.60 min/year.
- 99.99 gives 52.56. 99.5 gives 2628.
- A 525600 min model, not Prometheus.
- The next card times deploys / days, not an SLO.
99.9 gives 525.60 min/year
Year = 525600 × (100 − SLO) / 100. 99.9 gives 525.60 min/year. Not Prometheus.
- Error
- The gap from 100. 99.9 leaves 525.60 min/year. Not Grafana.
- Budget
- Year minutes. 99.99 gives 52.56 min/year. Not a live SLI.
- SRE
- A book model, not a probe. 99.5 gives 2628 min/year.
Examples
Example 2
- SLO 99.99
- 30 days
- used 10
52.56 min/year
What budget at 99.99? 52.56 min/year. The result is the year, not remainder after 10 min.
Example 3
- SLO 99.5
- 7 days
- used 60
2628 min/year
What budget at 99.5? 2628 min/year.
Related calculators
Common questions
What about SLO 99.9?
525.60 min/year. 525600 × 0.001. Not Prometheus.
What about 99.99?
52.56 min/year. Used 10 min does not change this primary.
What about 99.5?
2628 min/year. 525600 × 0.005.
Is this a live SLO from Prometheus?
No. The calculator multiplies 525600 by the gap. No metrics query.
Why days and used minutes?
They are in the fill. Extras show the year budget, not period remainder.
Does a comma in 99,9 work?
Yes. 99,9 and 99.9 are the same SLO.
How is this different from deploy frequency?
That card turns 14 and 7 into 2.00. Here 99.9 gives 525.60 min/year.
Does a 100% SLO count?
It yields 0 min/year. The examples keep 99.9, 99.99, and 99.5.
Is 525.60 a contract SLA?
No. It is a sketch from the typed SLO. The contract is outside this calculator.
Knowledge sources
The calculator counts bits, bytes or throughput from your numbers. Below are SI and bit definitions (NIST).
Page updated in 2026.
What an error budget is
An error budget is a concept from "Site Reliability Engineering" (the Google SRE book) — it is the allowed amount of unavailability implied by a given SLO. If the SLO is 99.9% availability, the error budget is the remaining 0.1% of time the system may be unavailable without breaking the promise made to users.
The formula
Budget = total minutes in the period × (100 − SLO%) / 100. For a year (525,600 minutes) that is 525600 × (100 − SLO) / 100. The calculator computes this automatically for a year, and if you supply any period in days, for that period too, subtracting any downtime already used if you provide it.
SLO and allowed downtime
| SLO | Downtime / year | Downtime / month (30 days) |
|---|---|---|
| 99% | ~3.65 days | ~7.2 hours |
| 99.9% | ~8.76 hours | ~43.2 minutes |
| 99.95% | ~4.38 hours | ~21.6 minutes |
| 99.99% | ~52.6 minutes | ~4.32 minutes |
| 99.999% | ~5.26 minutes | ~0.43 minutes |
MTTR and MTBF help interpret these downtime minutes in terms of incident cadence and repair speed; see the MTTR/MTBF calculator.
How teams "spend" the error budget
- An error budget is not just a number to report — it is a signal for how much risk a team can afford to take. A team with plenty of remaining budget can ship faster and experiment, e.g. testing new features in production.
- When the budget runs out, the standard SRE practice is a feature-release freeze, redirecting effort to stability until the budget rebuilds in the next window.
- It is a tool for the conversation between product teams (who want to ship faster) and operations teams (who want stability) — a concrete number of minutes instead of a subjective "is it stable enough" debate.
Rolling vs calendar windows
A budget can be tracked over a calendar window (month, quarter) or a rolling window (e.g. the last 30 days from today). A rolling window better reflects the service’s current state — it does not artificially "reset" on the first of the month — but requires slightly more monitoring complexity. This calculator computes a budget for the number of days you supply; whether that represents a calendar or rolling window depends on how you measure downtime used.
Examples
- SLO 99.9% → yearly budget of about 525.6 minutes (~8.76 hours) of allowed downtime.
- SLO 99.9%, 30-day period, 10 minutes already used → period budget about 43.2 minutes, about 33.2 minutes remaining.
- SLO 99.99%, 30-day period → period budget about 4.32 minutes — very little tolerance for downtime.