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Implied vs realized volatility: the gap option sellers live on

Implied volatility is the size of move the option's price expects. Realized volatility is the size of move the stock actually made. A seller is paid when the second is smaller than the first, and loses when it isn't.

Comparison · 6-minute read · Updated 2026-10-26

The short answer

Implied volatility (IV) is pulled out of the option's price. A high premium means the market expects big swings; a low one means it expects calm. It's a forecast baked into the price.

Realized volatility, also called Historical volatility, is measured from the stock's actual moves. It's what happened, not what was expected.

When the stock moves less than the premium implied, the seller keeps more than the move cost. When it moves more, the seller pays. That gap, in both directions, is the whole business.

Side by side

What the numbers mean in dollars

IV is quoted as a yearly percentage, which isn't much use on its own. The useful version is the expected move: roughly, the stock's price × IV × the square root of the time left, as a share of a year.

A $50 stock with an IV of 35% over 30 days expects a move of about $5 either way, give or take. Sellers use that number to place strikes. A $45 put sits right at the edge of the expected move.

Realized volatility answers the question later: did it move $2, or $9?

A worked example (an illustration, not a trade idea)

A made-up stock, XYZ, trades at $50. IV implies about a $5 move over the month. You sell the 30-day $45 put for $1.00. The premium is the market's payment for carrying a $5 swing.

The first three rows look the same. That's the seller's normal month: the stock did less than feared and the premium was kept. The last two rows are what the premium was really paying for. One of them costs nine quiet months.

Why IV is usually higher than what happens

Option buyers pay up for protection. Fear is worth more to people than calm, so most of the time the premium implies a bigger move than the stock then makes. Sellers are, in effect, selling insurance to nervous people.

But "usually" is not "always." Before earnings, IV jumps because a big move is likely, and the stock often delivers it. After a market shock, realized moves can run past implied ones for weeks. The gap sellers live on can close, and flip. Our IV crush guide shows what happens to the premium around earnings.

How sellers use the gap

• Sell when IV is high for that stock. The premium is paying more for the same strike. Comparing today's IV with the past year, often shown as IV rank, tells you whether it's high for this name.
• Don't sell just because IV is high. High IV before earnings is high for a reason. The expected move is real.
• Check realized moves too. If a stock has been swinging $8 a week and IV implies $5, the premium is cheap, not rich.
• Place the strike outside the expected move if you want most months quiet, and accept that the quiet months are paying for the loud ones.

This is why the wheel strategy works best on stocks you'd own anyway: the loud month ends with shares you wanted, not a loss you didn't. See implied volatility explained for how IV is read on a chain.

What to do with this

1. Find the IV and the expected move on a chain 30 days out, for one stock you follow.
2. Look at the chart. How far did it actually move in each of the last three months? Write the two numbers side by side.
3. If realized has been bigger than implied lately, the premium is not paying you enough for the strike you're looking at.

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