What does SLE stand for?
SLE stands for Single Loss Expectancy. The monetary loss from a single occurrence of a risk event: SLE = asset value × exposure factor.
SLE is the money lost each time one specific risk event happens. It is calculated as the value of the asset multiplied by the exposure factor, the share of that value lost in a single event. SLE is the first step of a quantitative risk assessment: it says how much one occurrence costs, not how often it happens.
SLE in practice: an example
A warehouse holds stock worth 200,000 dollars. A flood is expected to ruin a quarter of it, so the exposure factor is 0.25 and the SLE is 50,000 dollars. Whether floods are expected every year or once in twenty years does not change the SLE; that is what the ARO adds.
What SLE is confused with
SLE vs ALE: what is the difference?
SLE is the loss from one event. ALE is the expected loss per year: SLE multiplied by how many times a year the event is expected. What ALE stands for
SLE vs ARO: what is the difference?
SLE is an amount of money. ARO is a frequency. Multiplying the two gives the ALE. What ARO stands for
Which exams cover SLE?
SLE is on the official CompTIA acronym list for one of the four exams covered here.
- Security+ SY0-801: 5.2 (Security Program Management and Oversight).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. A server is worth 40,000 dollars and a power surge would destroy half of its value. What is the SLE?
- 80,000 dollars
- 40,000 dollars
- 20,000 dollars
- 2,000 dollars
Show the answer
C. 20,000 dollars. SLE is asset value times exposure factor: 40,000 times 0.5 is 20,000 dollars.
2. Which value is needed, together with the asset value, to calculate SLE?
- The exposure factor
- The recovery time objective
- The number of users
- The mean time between failures
Show the answer
A. The exposure factor. The exposure factor is the fraction of the asset's value lost in one event. The other values describe recovery or reliability, not the size of a single loss.
Sources: NIST IR 8286A, Identifying and Estimating Cybersecurity Risk for Enterprise Risk Management; NIST SP 800-30 Rev. 1, Guide for Conducting Risk Assessments. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.