What Is Value at Risk (VaR)? Measuring a Portfolio's Potential Loss
VaR answers a specific question: under normal conditions, what is the most my portfolio might lose over a period, at a given probability? How to read it correctly and the critical limits you must keep in mind.
Saying "my portfolio is pretty risky" is vague. Value at Risk β VaR β tries to turn that vague feeling into a concrete number: under normal market conditions, how much you might lose at most, over a period, at a given confidence level.
What question VaR answers
A complete VaR statement always has three parts: an amount, a time horizon, and a confidence level.
For example: "The 1-day VaR at 95% confidence is $800" means: under normal conditions, on about 95% of days the portfolio won't lose more than $800; only about 5% of days (on average 1 in 20) might the loss exceed that figure.
The key point: VaR does not say "maximum loss of $800." It says "95% of the time, no more than $800" β and stays silent on how bad the other 5% gets.
Why VaR is useful
- It standardizes risk into one number that's easy to compare across different portfolios or assets.
- It forces you to think in probabilities, rather than only expected return.
- It helps size positions: if VaR exceeds what you can tolerate, that's a signal to trim or diversify further.
Three critical limits to remember
VaR is easy to misread, and those misreadings have contributed to major financial failures. Three points to burn in:
- VaR says nothing about the tail. It gives the threshold exceeded with small probability, but not how much you lose when it's exceeded. The loss in the worst 5% can be far larger than VaR. (A complementary measure is "expected shortfall" β the average loss in the worst-case scenarios.)
- VaR assumes "normal conditions." Most calculations assume volatility like the past. In a crisis, correlations between assets tend to spike and everything falls together β exactly when VaR is most optimistic.
- VaR is only as good as its inputs. A precise-looking number can create false comfort, leading people to take on more risk because it's "been measured."
How to use VaR well
VaR is one tool in the box, not the final answer. For an individual investor, its greatest value is a shift in mindset: it forces you to ask "how much could I lose, at what probability," instead of only dreaming about returns.
Always pair VaR with a tail question: "If the worst 5% scenario happens, can I withstand it?" A resilient portfolio isn't the one with the smallest VaR, but the one where even if the tail event occurs, you stay standing and aren't forced to sell in a panic. Measuring risk is the first step; preparing for the scenario beyond the measure is real risk management.