Volatility indicators: how far a price swings, and what that means for you

Volatility is how widely a price swings. Volatility indicators such as Bollinger Bands, Average True Range (ATR) and standard deviation measure the size of those swings, not their direction.

Traders use them to spot quiet and wild periods and to size stop-losses. For a long-term saver, the bigger lesson is simpler: the more a price swings, the less you can rely on it for money you need soon.

What volatility means

Picture two prices that both end the month where they started. One moved a few piasters a day. The other jumped up and down by several pounds. The second is more volatile.

Volatility says nothing about whether a price will rise or fall. It tells you how bumpy the road is. A bumpy road matters most if you might have to get off at a bad moment.

Standard deviation in plain words

Standard deviation measures how far values usually sit from their average. Small spread, small number. Big spread, big number. When people talk about "historical volatility", they usually mean the standard deviation of past price changes.

If price changes followed a bell curve, about 68% would fall within one standard deviation of the average and about 95% within two, StockCharts explains. Real prices don't follow a bell curve neatly: big surprise moves happen more often than that maths suggests.

Bollinger Bands

John Bollinger built his bands in the 1980s. His own site gives the defaults:

• Middle band: a 20-period simple moving average of the price.
• Upper and lower bands: 2 standard deviations above and below that average.

When swings grow, the bands widen. When the market goes quiet, they narrow. StockCharts notes that Bollinger expects the bands to hold about 88-89% of price action.

Example, not market data. Say a share's 20-day average is EGP 50 and the standard deviation is EGP 2. The bands sit at 50 − (2 × 2) = EGP 46 and 50 + (2 × 2) = EGP 54, a width of EGP 8. If the standard deviation shrinks to EGP 0.75, the bands move to EGP 48.50 and EGP 51.50, a width of just EGP 3.

The squeeze

That narrowing is called "the squeeze". Bollinger tracks it with a related measure, BandWidth. The idea is that calm periods are often followed by bigger moves. A squeeze does not say which way the move will go.

Walking the bands

In a strong trend, a price can keep touching the upper band (or the lower one) for weeks. Bollinger calls this walking the bands. So a touch is not, by itself, a sign that the price has gone "too far".

Average True Range (ATR)

J. Welles Wilder introduced ATR in his 1978 book New Concepts in Technical Trading Systems. He wanted a measure that counts gaps, when a price opens well above or below the previous close.

The true range of a day is the largest of three numbers:

1. Today's high minus today's low.
2. Today's high minus yesterday's close (ignoring the minus sign).
3. Today's low minus yesterday's close (ignoring the minus sign).

ATR is the average true range, usually over 14 days. The first value is a simple average of 14 true ranges. After that, StockCharts gives Wilder's smoothing: (previous ATR × 13 + today's true range) ÷ 14.

Worked example: four days in EGP

Example, not market data. A made-up share, with prices in EGP:

Day 2 opened with a gap up and day 3 with a gap down. High minus low was only EGP 2 every day, but the true range catches the gaps.

Average true range over these four days: (2 + 4 + 4 + 2) ÷ 4 = 12 ÷ 4 = EGP 3. Using high minus low alone would give EGP 2 and understate the swings by a third. A real ATR would use 14 days and Wilder's smoothing; four days just shows the idea.

ATR depends on the price

ATR is in pounds, not percent. A EGP 10 share will usually have a smaller ATR than a EGP 200 share, so raw ATRs can't be compared across shares. Dividing ATR by the price turns it into a percentage (StockCharts calls this ATRP).

How people use ATR to size a stop-loss

A stop-loss is a price at which you plan to sell to limit a loss. A stop set too close gets hit by normal daily noise. ATR is one way to set it outside that noise.

Example, not market data. Using the share above, the price is EGP 51 and ATR is EGP 3.

A EGP 48 stop is one ordinary day's range away, so a normal swing could trigger it. A EGP 45 stop gives more room, but each share can lose EGP 6.

Traders then work backwards. If you decided you could lose at most EGP 600 on this position, 600 ÷ 6 = 100 shares, or 100 × 51 = EGP 5,100 invested. One well-known variant, the Chandelier Exit, places a stop at the 22-day high minus 3 × ATR.

EGX price limits and trading halts

The Egyptian Exchange caps how far a price can move in one session. We couldn't open egx.com.eg, so these rules come from an EFG Hermes market information page we read in October 2026, which shows no effective date:

• Daily limit: a share can move up to 20% above or below the previous close.
• Stock pause: if a share's moving average traded price moves 10% from the previous close, trading in it stops for 10 minutes.
• Market-wide pause: large falls in a broad index can halt trading in all shares. The thresholds have changed over time; one change, made with the FRA, was reported in October 2021.

These rules matter for indicators. A share stuck at its daily limit shows a smaller range than the pressure behind it, and the move can continue next day as a gap. Check the current rules with your brokerage.

Where volatility indicators mislead

• They look backwards. Every one of them is built from past prices. Calm can end suddenly.
• No direction. A wide band or a high ATR says "big moves", not "up" or "down".
• Settings change the answer. Bollinger calls 20 and 2 "defaults"; other periods give other bands.
• Thin trading. In shares with little liquidity, a few small trades can swing the price and the indicator.
• Bell-curve maths. Moves beyond two standard deviations happen more often than the textbook figure suggests.

What volatility means for a long-term saver

The SEC's guide on asset allocation says stock volatility makes them very risky in the short term. Your time horizon (how long until you need the money) decides how much that matters.

Example, not market data. Say you hold EGP 100,000 in shares and the market falls 30%. You now have EGP 70,000. If you can wait years, you have time for a recovery, though none is promised. If you need the money next month for rent or a hospital bill, you must sell at the low.

That's why your emergency fund comes first, in cash or a bank product you can reach quickly. Money for goals within a few years usually doesn't belong in volatile assets either.

Your plan

1. Build your emergency fund first. Keep 3 to 6 months of essential costs out of the stock market (see our emergency fund guide).
2. Match money to time. Only put into shares money you won't need for several years.
3. Look at the range, not just the trend. Before you buy anything, note how far its price has swung (ATR as a percent of price is a quick check).
4. Size positions by the worst ordinary swing. Ask: could I live with a 2 × ATR fall, or a 30% fall, without selling?
5. If you use stops, write them down before you buy, and remember gaps and EGX limits can carry the price past them.
6. Learn the order types your brokerage offers before you need them.

What to watch out for

• Indicator-driven trading. Buying every squeeze or band touch is speculation, not investing.
• Fees. Each trade has brokerage and exchange fees. Frequent stop-outs and re-entries add up.
• Tips built on charts. A chart pattern shared in a group is not research into the business behind the price.
• Mixing up calm and safe. A quiet price can still drop sharply; low volatility is not low risk.

This guide is for education only. It is not advice to buy or sell any share, fund or other investment.