Change Impact Calculator
Score a network change's risk from blast radius, rollback feasibility, testing and timing, then get a recommended approval path.
Inputs
Change Risk Score
16.7/100
Risk Level
Informational
Blast Radius
25.0%
User-Minutes at Risk
125,000
Recommended Approval Path
Pre-approved standard change
Step by step
Values used
Users affected if the change fails = 5,000 users; Total users on the network = 20,000 users; Expected service interruption = 5 minutes; Time to roll back = 20 minutes; Change validated in a lab or staging network = Yes; Executed inside an approved maintenance window = Yes
Change Impact
risk = blast radius × 0.4 + outage score (20) + rollback score (15) + 15 if untested + 10 if outside a window.
Change Risk Score
= 16.7 /100
Risk Level
= Informational
Blast Radius
= 25.0
User-Minutes at Risk
= 125,000
Recommended Approval Path
= Pre-approved standard change
How it works
Blast radius carries the most weight because it scales the consequence of everything else. Outage and rollback durations are scored against a one-hour reference, and the two flags add fixed penalties for the practices that most reliably turn a change into an incident. Change-related failures are the largest single cause of network outages, and a numeric score is what makes the approval path defensible rather than political.
Formula
Change Impact
risk = blast radius × 0.4 + outage score (20) + rollback score (15) + 15 if untested + 10 if outside a window.
- blast radius
- Affected users as a percentage of the total base
- user-minutes
- Affected users × (outage + rollback time)
Frequently Asked Questions
How is Change Impact calculated?
risk = blast radius × 0.4 + outage score (20) + rollback score (15) + 15 if untested + 10 if outside a window. Blast radius carries the most weight because it scales the consequence of everything else. Outage and rollback durations are scored against a one-hour reference, and the two flags add fixed penalties for the practices that most reliably turn a change into an incident.
Why does Change Impact matter?
Change-related failures are the largest single cause of network outages, and a numeric score is what makes the approval path defensible rather than political.
What values do I need to enter?
This calculator takes 6 inputs: Users affected if the change fails, Total users on the network, Expected service interruption, Time to roll back, Change validated in a lab or staging network, Executed inside an approved maintenance window. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
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