What is implied volatility?
Updated 12 July 2026 · by Theo Chen
Implied volatility (IV) is the options market's forecast of how much a stock will move over the life of an option, expressed as an annualised percentage. It is not measured directly but implied by option prices: rich prices mean big expected moves and high IV. IV is the single biggest lever on the premium an option pays.
Want to know whether a stock's IV is actually high or low right now? Raw IV needs context — the IV Rank calculator compares it to the past year so you can tell a good time to sell from a bad one.
Open the IV Rank Calculator →What IV actually measures
An IV of 30% means the market expects the stock to stay within roughly ±30% of its price over the next year, at one standard deviation (about a 68% chance). Scale that to the option's actual life and it becomes the expected move — the range the market is pricing for that expiration. When you sell an option, IV is literally what you are being paid: the higher it is, the fatter the premium, because the market is paying up for the bigger expected swing.
IV measures size, not direction
This is the part newcomers miss. A stock with high IV is expected to move a lot — but IV says nothing about which way. That is exactly why premium-selling strategies lean on it: a covered call or cash-secured put seller is not betting on direction, they are betting that the real move will be smaller than the IV-implied one. When implied volatility runs higher than the volatility that actually shows up, the seller keeps the difference.
High IV, low IV, and the seller's sweet spot
More IV is not simply "better." High IV pays more, but it is usually pricing a real, identifiable risk — an earnings report, an FDA decision, a lawsuit — and a sharp adverse move will cost you far more than the extra premium earned. Very low IV barely compensates you for the risk you take. Most sellers look for a moderate band — roughly 20–45% on a quality underlying — where the premium is meaningful and the move is not pricing a binary event. The relationship between IV and the daily decay you collect is covered under theta, and the sensitivity of an option's price to IV itself is vega.
Why isn't a raw IV number enough?
An IV of 35% tells you nothing until you know where that stock's IV usually sits. 35% is low for a volatile growth name and high for a staid blue chip. IV Rank and IV Percentile fix this by comparing today's IV to its own range over the past year — so a high IV Rank flags a genuinely good time to sell premium, not just a big-sounding number. That comparison is the practical way IV gets used, and it is what the IV Rank calculator computes.
The bottom line
A raw implied volatility number is meaningless without context - 30% can be high for one stock and low for another, so use IV Rank to compare it against the stock's own past year before deciding it is a good time to sell premium.
Frequently asked questions
What is implied volatility in simple terms?
Implied volatility (IV) is the market's estimate of how much a stock will move over the life of an option, expressed as an annualised percentage. It is "implied" because it is backed out of the option's price rather than measured directly: if traders are paying a lot for options, they expect big moves, so IV is high. It says nothing about direction — only the expected size of the move.
Is high or low IV better for selling options?
Higher IV pays sellers more premium, because the options you sell are richer. But high IV usually reflects real risk — an earnings report, a pending decision — so a bigger premium comes with a bigger expected move against you. The comfortable middle for most premium sellers is moderate IV (roughly 20–45% on quality names): enough premium to be worth it, without pricing a binary event.
What is the difference between implied and historical volatility?
Historical (or realised) volatility measures how much the stock actually moved in the past. Implied volatility is forward-looking — the move the market expects from here, derived from current option prices. Option sellers have an edge when implied volatility runs higher than the volatility that ends up being realised, because they were paid for movement that did not happen.
How do I know if IV is high or low for a stock?
A raw IV number means little on its own — 30% might be high for one stock and low for another. Use IV Rank or IV Percentile, which compare the current IV to its own range over the past year. An IV Rank near 100% means IV is near its yearly high (good for selling); near 0% means it is near its low. The IV Rank calculator does this comparison for you.
Does implied volatility predict which way a stock will move?
No. IV measures the expected size of the move, not the direction. A stock with high IV is expected to move a lot — up or down. That is why IV is central to premium-selling strategies, which profit from movement being smaller than expected, rather than from guessing direction.
Related questions
- How do IV rank and IV percentile differ?
- What is the expected move that IV implies for an expiration?
- What is vega, the Greek that prices an IV change?
- Which Greeks matter most when selling options?
Related tools and guides
Put IV to work: rank it with the IV Rank Calculator, turn it into a price range with the Expected Move Calculator, and see it drive option prices and Greeks in the Black-Scholes Calculator. For the seller's playbook on timing, read IV Rank vs IV Percentile and the Greeks for option sellers.
Educational information only — not financial advice. Implied volatility is a market estimate, not a guarantee; actual moves can and do exceed it. Always size positions to your own risk tolerance.