Studies · Volatility
Historical Volatility
historicalVolatility · Annualised σ of log returns, as a decimal
Drawn in its own panelReads one column (close here)
Hover the chart to read values · practice data: a seeded random walk with no overnight gaps
What it measures
The standard deviation of daily log returns over the window, annualized by multiplying by the square root of the number of trading periods in a year. It is the textbook "realized vol" calculated straight from prices.
How traders use it
- Compare with implied volatility to judge whether options are rich or cheap.
- Track volatility regimes: low historical vol tends to be followed by higher vol, and the reverse (volatility mean-reverts).
- Size positions and set expectations for how far a stock might move.
Parameters
| Name | Value | Default | Allowed | What it does |
|---|---|---|---|---|
| period | 20 | ≥ 1 usual 10–60 | Number of returns in the window. 20 is about one trading month. | |
| annualize | 252 | any usual 1–365 | Periods per year used to scale up: 252 for daily bars, 52 for weekly, 12 for monthly. |
Good to know
The output is a decimal: 0.25 means 25% annualized volatility.