Skip to content
ENExplore Calculators

Change Impact Calculator

Score a network change's risk from blast radius, rollback feasibility, testing and timing, then get a recommended approval path.

About Change Impact Calculator

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)

Worked example

With the default values below, Change Impact Calculator returns Change Risk Score of 16.7. Change any input above and every figure here is recalculated in your browser.

Inputs used

Users affected if the change failsaccepts 0–100,000,000 users
5,000 users
Total users on the networkaccepts 1–100,000,000 users
20,000 users
Expected service interruptionaccepts 0–100,000 minutes
5 minutes
Time to roll backaccepts 0–100,000 minutes
20 minutes
Change validated in a lab or staging network
Yes
Executed inside an approved maintenance window
Yes

Results

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

  1. 1Values used
  2. 2Change Impact
  3. 3Change Risk Score= 16.7 /100
  4. 4Risk Level= Informational
  5. 5Blast Radius= 25.0
  6. 6User-Minutes at Risk= 125,000
  7. 7Recommended Approval Path= Pre-approved standard change

Assumptions and limits

  • The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, 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

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.

Related Calculators

Change Impact Calculator | Calcrivo