Direct Answer
Realized volatility is the annualized square root of the realized variance computed from squared returns over a window. It summarizes how much the price actually moved, not what options imply. Larger values mean the instrument has been moving more.
Realized Volatility: Formula, Meaning, Signals, Examples and How to Use It
How Is Realized Volatility Calculated?
Realized volatility is the annualized square root of the realized variance computed from squared returns over a window. It summarizes how much the price actually moved, not what options imply.
Formula: RV = sqrt( (252 / n) x sum of r_i^2 ), with r_i the daily log returns over n days
Inputs:
- Daily (or intraday) log returns
- Window length n
- Annualization factor (commonly 252 trading days)
Worked example. A sum of squared daily returns of 0.0028 over 21 trading days annualizes to 18.3%. The inputs are illustrative numbers, not market data.
Reading it. Larger values mean the instrument has been moving more. It is the realized counterpart to implied volatility, and the gap between them is the volatility risk premium.
Limits. It is backward looking and depends on window, sampling frequency and annualization convention (252 versus 365 days). Squared returns without a mean adjustment assume near-zero drift, and one large move can dominate a short window.
What is Realized Volatility?
Realized volatility is the annualized square root of the realized variance computed from squared returns over a window. It summarizes how much the price actually moved, not what options imply.
How to use Realized Volatility
Larger values mean the instrument has been moving more. It is the realized counterpart to implied volatility, and the gap between them is the volatility risk premium. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime.
Strengths
- Annualizing with 252 over n scales the sum of squares to a per-year rate, so a 20-day and a 60-day window read on the same scale.
- It summarizes actual price movement with one number that can be set beside an implied volatility quoted in the same annualized terms.
- Reproducible when the formula and data convention are fixed.
Weaknesses and limitations
- A square root of an average is concave, so realized volatility is slightly biased low relative to the square root of the true variance.
- Overlapping rolling windows share most of their returns, so successive readings are strongly correlated and not independent observations.
- Correlated indicators can create false confidence by repeating the same underlying information.
Editorial and risk note
This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance.
Frequently Asked Questions
Is Realized Volatility a buy or sell signal?
No. Larger values mean the instrument has been moving more. It is backward looking and depends on window, sampling frequency and annualization convention (252 versus 365 days). A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions.
What is the best setting for Realized Volatility?
Realized Volatility takes these inputs: daily (or intraday) log returns; window length n; annualization factor (commonly 252 trading days). There is no universal best setting for the tunable ones, so test them across instruments, regimes and out-of-sample periods and favor stable parameter regions over one historical winner.
Can Realized Volatility be used by itself?
It is backward looking and depends on window, sampling frequency and annualization convention (252 versus 365 days). Squared returns without a mean adjustment assume near-zero drift, and one large move can dominate a short window. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone.
Does Realized Volatility work on every timeframe?
The calculation (RV = sqrt( (252 / n) x sum of r_i^2 ), with r_i the daily log returns over n days) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it.
Why does Realized Volatility give false signals?
A square root of an average is concave, so realized volatility is slightly biased low relative to the square root of the true variance. Overlapping rolling windows share most of their returns, so successive readings are strongly correlated and not independent observations. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated.
How should Realized Volatility be backtested?
Rebuild Realized Volatility from daily (or intraday) log returns using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline.