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Implied vs historical volatility: is this premium rich or just risky?
Historical volatility measures how much a stock has actually moved. Implied volatility is how much option prices say it will move. When IV sits well above HV, sellers are being paid extra, unless the market knows something the past doesn't show.
The short answer
Historical volatility (HV) is how much a stock has moved, measured from its past daily price changes. Implied volatility (IV) is how much the market expects it to move, backed out of today's option prices.
For a seller, the gap is the point. If IV is well above HV, the premium is priced for bigger moves than the stock has been making. That extra is what sellers are paid for. But the gap is a clue, not a promise: sometimes IV is high because a big event is coming.
What historical volatility measures
HV looks backward. It takes the stock's daily percent changes over a set window, often 20 or 30 trading days, and works out how spread out they were. Then it scales that up to a yearly number so it can sit next to IV.
A rough feel for it: a stock whose typical daily move is about 1.6% has an HV near 25%. A stock that typically moves 2.5% a day has an HV near 40%. The Historical volatility glossary page has the one-line definition.
HV depends on the window. A 20-day HV reacts fast to a recent shock. A one-year HV is smoother. Check which one your broker shows.
What implied volatility measures
IV looks forward. Nobody sets it directly. It's the volatility number that, plugged into a pricing model, gives the option price people are actually paying.
So IV bundles the market's fear, events on the calendar (earnings, a drug trial result, a court date) and plain supply and demand. When lots of traders want protection, IV rises.
The gap, and what it pays
A made-up stock, XYZ, trades at $50. Its 30-day HV is 25%. Its 30-day options trade at 40% IV. Here's a 30-day $48 put priced both ways with a standard model (an illustration, not a trade idea).
| Volatility used | Rough put price | What it means |
|---|---|---|
| 25% (what the stock has done) | $0.60 | A "fair" price if the future looks like the past |
| 40% (what the market is charging) | $1.30 | What you'd actually collect |
The gap is about $0.70 a share. That's the market pricing in bigger moves than XYZ has been making. If XYZ keeps moving like its HV, the seller collected more than the risk turned out to be.
If XYZ moves more than its IV, the seller collected too little.
The worked example, outcome by outcome
You sell the $48 put for $1.30 and collect $130. Your broker sets aside $4,800.
| XYZ at expiry | What happens | Shares | Premium | Total result |
|---|---|---|---|---|
| $53 | Put expires | — | +$130 | +$130 |
| $48 | Put usually expires; maybe assigned | $0 | +$130 | +$130 |
| $46.70 | Assigned at $48 | −$130 | +$130 | $0 (break-even) |
| $45 | Assigned at $48 | −$300 | +$130 | −$170 |
| $40 | Assigned at $48 | −$800 | +$130 | −$670 |
A 40% IV says the market's one-standard-deviation guess for 30 days is roughly $5.70 either way. A 25% HV says the stock has been moving more like $3.60. The $40 row is a move bigger than either. That's a math example, not a promise.
Why the gap might be there
| What you see | A common reason | What it means for a seller |
|---|---|---|
| IV well above HV, earnings inside the expiry | The market is pricing the report | Premium is high because a gap is possible. The HV hasn't seen it yet. |
| IV well above HV, market-wide fear | Everyone is buying protection | Premium may be rich, but moves can stay large for a while |
| IV well above HV, nothing on the calendar | Fear has outrun the stock's actual moves | The cleanest case for sellers, if the business is sound |
| IV close to HV | The market sees the future like the past | Fairly priced; no extra pay |
| IV below HV | The stock just had a wild stretch that's expected to calm | Premium may be thin for the risk |
The first row is the trap. IV before earnings is almost always above HV, because HV can't "see" the report coming. The extra premium isn't a gift. It's the price of a known event. Earnings inside my option expiry walks through that case.
How to read it in practice
- Find both numbers. Most broker platforms show IV on the Options chain. HV is often on the stock's overview or a volatility tab. Some call it "realized" volatility.
- Match the windows. Compare 30-day IV with 20- or 30-day HV, not a one-year number.
- Check the calendar. Earnings, dividends, a product launch, a ruling. If one sits inside your expiry, the gap is probably about that.
- Compare IV with its own past. IV rank and IV percentile show where today's IV sits in its own range. See IV rank for picking stocks.
- Decide if you'd still own the stock at the strike. The gap doesn't change that question.
In plain words: IV is the price. HV is the recent track record. When the price is well above the track record and there's no event on the calendar, sellers are being paid extra for fear.
How this fits the wheel
In the wheel strategy, you sell options again and again. Over many trades, the habit of selling when IV sits above HV tends to mean you're paid more for each unit of risk. That's a tendency many sellers rely on, not a law. It has failed badly in sudden crashes, when actual moves blew past what IV priced.
Pair it with vega and IV for option sellers: high IV when you sell is good, but IV rising further while you hold is not.
Questions
What is the difference between implied and historical volatility?
Historical volatility measures how much the stock actually moved in the past. Implied volatility is how much option prices say it will move in the future. One is a record, the other is a forecast built into a price.
Is it good to sell options when IV is higher than HV?
It means you're being paid for bigger moves than the stock has recently made. That's often a reason sellers like it. But check for earnings or news first, because a known event is the most common reason for the gap.
Where do I find historical volatility?
Many broker platforms show it on the stock's page or a volatility chart, sometimes called realized volatility. If yours doesn't, check the platform's help pages or a charting tool that lists it.
Can implied volatility be lower than historical volatility?
Yes. After a wild stretch, the market may expect calmer days ahead, so IV sits below recent HV. In that case premiums may be thin compared with how much the stock has been moving.
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