What Is Volatility (Standard Deviation)?
Some stocks swing 5% up and down even in a single day, while some assets stay calm for years. What if you could express this 'size of the swing' as a single number? That's exactly volatility—standard deviation.
What is volatility?
Volatility is a metric that indicates how much returns are scattered from their mean. In finance, it's usually measured by the standard deviation of returns (σ, sigma).
Simply put, it's 'how much the price swings' turned into a number. If the ups and downs around the mean are large, volatility is high; if it stays quietly near the mean, volatility is low.
The important point is that volatility includes both rises and falls. An asset that rises a lot and an asset that falls a lot are both described as 'high volatility.' So volatility is closer to 'the size of uncertainty' than to 'risk.'
Volatility is not a value that guarantees or predicts future losses. It's merely a summary, from past data, of 'how much it could swing.'
How do you compute standard deviation?
Standard deviation is obtained by squaring how much each period's return deviated from the mean, averaging those, and then taking the square root. More important than the calculation itself is the sense of it as 'a representative value for how much things deviated from the mean.'
One useful thing to know is the 'square-root-of-time rule.' Volatility grows in proportion to the square root of the period as the horizon lengthens. So to convert daily volatility to annual, you multiply by the square root of about 252 (the trading-day convention), and to convert monthly to annual, by the square root of 12.
For example, if daily volatility is 1%, the annualized volatility comes to roughly 1% × √252 ≈ 15.9%. Expressions like 'annual volatility of 20%' seen in the news are mostly values annualized this way.
Daily→annual multiplies by √252, and monthly→annual by √12. The key is that you multiply by the 'square root,' not simply by the period. (Source: Motley Fool, Macroption)
Volatility across assets, in numbers
Looking at actual historical figures, volatility differs greatly by asset.
The S&P 500 (large U.S. stocks) has had a long-run annualized volatility of roughly 20% (about 19–20%) since 1926. Over the recent 2020–2025 window, it's sometimes measured somewhat lower, at about 17%. Since the value changes by period, it's right to understand it as 'roughly this range' rather than 'exactly some %.'
Gold is relatively lower, at about 15% a year on a recent basis. Bitcoin, by contrast, was about 52% a year as of early 2025, and in its early days its swings were large enough to exceed 200% a year. Individual growth stocks (e.g., some tech stocks) also sometimes show volatility on par with Bitcoin, in the 45–55% a year range.
The figures vary by measurement period and method. The values here are approximate ranges cross-checked across several sources. (Source: Crestmont Research, Fidelity, macrotrends)
Volatility and maximum drawdown (MDD) are different
Volatility is often called a 'risk metric,' but its flavor differs a bit from the pain an actual investor experiences.
Volatility counts rising moves and falling moves equally as 'swings.' So an asset that rises a lot and falls a lot comes out with high volatility. Maximum drawdown (MDD), by contrast, looks only at the 'decline' from peak to trough. The pain of your account actually being cut in half is shown more intuitively by MDD than by volatility.
The two metrics complement each other. Even with low volatility, MDD can be large if it slides down steadily, and even with high volatility, MDD can be relatively small if it recovers quickly after a plunge. A long-term investor should look together at 'how much it swings normally (volatility)' and 'how much it falls at the worst moment (MDD).'
Frequently Asked Questions
Q. If volatility is high, is it automatically a bad asset?
No. Volatility is just 'the size of the swing,' not a judgment of good or bad. High volatility means the uncertainty that it could fall a lot or rise a lot. What matters is whether you can endure those swings and hold for the long term. If you can't endure and sell at the bottom, high volatility turns into an actual loss.
Q. Are volatility and standard deviation the same thing?
In practice they're used almost interchangeably. In finance, the volatility of returns is mostly calculated as the standard deviation of returns. That said, understand 'volatility' as the broad word for the concept and 'standard deviation' as the specific statistic that measures that concept.
Q. What does annual volatility of 20% actually feel like?
As a rough sense, an asset with 20% annual volatility means its one-year return can be scattered fairly widely around the mean. It means the range between good years and bad years is large—not that a 20% loss will necessarily occur. Remember it's just a reference summarizing past values, not a number that fixes the future.
📋 Results are based on historical data; past returns do not guarantee future returns.
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