Volatility
What is volatility?
Volatility measures how much an investment's price moves around, usually as the standard deviation of returns. It describes turbulence, not the probability of permanent loss.
- Written by
- Pro Investor Academy Research Team
- Content type
- Reference definition
- Published
- 2026-09-13
- Last reviewed
- 2026-09-13
Movement is not risk
For a long-term owner, a central risk is a business that permanently deteriorates. A price fall is an economic loss in value whether or not you sell — selling only turns it into a realised (locked-in) loss and removes the chance to benefit if the price recovers. Volatility matters most when it forces a sale at a bad moment, or when the fall reflects real damage to the business.
Position size is the practical control
You cannot lower an investment's volatility, but you can choose how much of your portfolio experiences it.
A worked example
Two holdings can end a year at the same price, one having drifted quietly and one having fallen 35% in between. Same return, very different experience.
The mistake people make
Avoiding volatility entirely and accepting returns that fail to outpace inflation over decades.
How we use it
Share-price volatility feeds our separate Price Risk check, which sorts companies into lower, normal or higher price-risk groups and can decide whether a company is ranked at all. It is not part of Risk Intelligence, which measures business risk from company filings (30% of the Pro Investor Score, tied with Long-Term Potential).
Related terms
Sources and methodology
- Investor.gov investor education — U.S. Securities and Exchange CommissionPrimary source
- Intelligent Accumulation methodology — Pro Investor AcademyPrimary source
Keep reading
- Investing Glossary
Every investing term we use, defined once and in plain English — from compounding and drawdown to Form 13F and share dilution.
- Compound interest
Compound interest is growth earned on both your original money and on the growth it has already produced. It is the reason long holding periods matter more th
- Dollar-cost averaging
Dollar-cost averaging means investing a fixed amount on a fixed schedule regardless of price. It removes the need to decide when to invest, and it buys more s
- Free cash flow
Free cash flow is the cash a business has left after paying the costs of running and maintaining itself. It is the cash that can fund dividends, buybacks, deb
- Expense ratio
An expense ratio is the annual percentage of your money a fund keeps to run itself. It is deducted from returns quietly, every year, whether the fund performs
- Maximum drawdown
Maximum drawdown is the largest peak-to-trough fall an investment has suffered over a period. It measures the worst stretch an investor would have had to sit
Educational information only. Nothing here is a recommendation to buy or sell any investment, and no research measurement removes the risk of loss.