Calculators
Risk Quantification Calculator
Quantify a risk with single and annualised loss expectancy and calculate the return on a security control.
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The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Prioritising security investments
- Justifying a control to finance
- Comparing alternative controls
- Preparing a risk register in money terms
About this tool
What the Risk Quantification Calculator does
Quantitative risk analysis prices a risk in money. Single loss expectancy (SLE) is asset value × exposure factor; annualised loss expectancy (ALE) multiplies SLE by how often the event happens each year. Comparing ALE before and after a control with its cost gives the return on security investment.
Formula
- SLE = asset value × exposure factor
- ALE = SLE × annual rate of occurrence
- ROSI = (ALE before − ALE after − control cost) ÷ control cost
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Asset value | $500,000 |
| Exposure factor | 40% |
| Annual rate of occurrence | 0.3 |
| Reduction from the control | 60% |
| Annual cost of the control | $25,000 |
| Result | Value |
|---|---|
| Annualised loss expectancy | $60,000 |
| Return on security investment | 44.0% |
| Single loss expectancy | $200,000 |
| ALE with the control | $24,000 |
| Annual risk reduction | $36,000 |
How to read the result
The inputs are estimates, so present a range: run the calculator with cautious and pessimistic assumptions and show both.
A negative ROSI does not always mean a control is unjustified; legal or contractual obligations can require it regardless.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
The expected yearly cost of a risk: single loss expectancy multiplied by the number of times the event is expected each year.
The percentage of an asset's value lost if the event happens.
Subtract the control's cost from the risk reduction it delivers, then divide by the control's cost.
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