What standard deviation shows
Standard deviation is a volatility indicator. It measures how far recent prices have spread away from their average, called the mean. When prices stay close to the average, the line is low. When prices swing far from it, the line rises.
It shows only the size of movement. It does not show direction. A sharp rally and a sharp fall can both produce the same high reading.
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The formula
For a chosen period of N bars:
- Calculate the moving average of the closing prices. This is the mean.
- For each bar, subtract the mean from the close and square the result.
- Take the average of those squared differences.
- Take the square root of that average.
The result is in price units, the same units as the chart. That is why the same reading means different things on EURUSD and on XAUUSD. In MetaTrader you can change the period, the moving average method (simple, exponential, smoothed, linear weighted) and the applied price. The default values are shown in the indicator's settings window.
How to add it in MT4 and MT5
In both MetaTrader 4 and MetaTrader 5:
- Open the chart of the instrument you want to study.
- Go to Insert → Indicators → Trend → Standard Deviation.
- Set the period, MA method and applied price, then confirm.
The indicator opens in a separate window below the price chart. You can practise on a demo account before using it with real money.
How to read it: a drawn example
The sketch below is drawn by hand and does not show real prices.
- Low, flat line: price is moving in a tight range and volatility is compressed.
- Rising line: price is moving away from its average quickly, in either direction.
- Falling line after a spike: the move is slowing and prices are settling closer to the mean.
How to use standard deviation
Traders commonly use it to:
- Compare current volatility with recent volatility. This helps judge whether a market is quiet or active.
- Size stops and positions. A wider spread of prices suggests wider stops and smaller position size. See risk management.
- Understand Bollinger Bands. Bollinger Bands place lines a set number of standard deviations above and below a moving average.
- Spot volatility compression. Long low readings often come before breakouts, but the indicator cannot tell which way price will move.
Parameter choices for experienced traders
- Short period: reacts quickly and is noisy. It suits intraday monitoring but gives frequent false spikes.
- Long period: smoother and slower. A spike stays in the reading for many bars after the move has ended.
- MA method: an exponential mean shifts faster, so deviations look smaller during strong trends than with a simple mean.
- Cross-instrument work: because the output is in price units, divide it by price or compare it to ATR before comparing different symbols.
Where it misleads
- Trends inflate it. In a steady trend, price moves away from a lagging mean. The reading rises even though bar-to-bar movement is smooth.
- Fat tails. Market returns do not follow a normal distribution. Moves "beyond" several deviations happen more often than textbook statistics suggest.
- Gaps and news. A single gap or news candle can lift the line for the whole period.
- Session effects. Thin hours, such as the late US session for Pakistan-based traders, look calm. Volatility can then rise sharply.
- Lag. It describes the bars that have already closed. It does not predict what comes next.
Leveraged forex and CFD trading can lose money fast. No volatility reading removes that risk. For more tools, see technical analysis and leading vs lagging indicators.
Frequent questions
Is standard deviation a buy or sell signal?
No. It measures how much prices are dispersed, not which way they are heading.
What is standard deviation in forex used for most?
Traders mainly use it to judge current volatility, plan stop distance and position size, and build Bollinger Bands.
How is it different from ATR?
ATR measures the average range of each bar, including gaps. Standard deviation measures how far closes spread from their mean.
Why does the reading differ so much between symbols?
The output is in price units, so instruments with higher prices show larger values. Normalise the reading before comparing symbols.
Does it repaint?
No. Values on closed bars stay fixed. Only the current, unfinished bar changes. See repainting indicators.