Why the IV Number Next to Each Strike Isn't the Same Number
IV is solved per contract, not per stock
Scroll down any option chain and the IV column rarely holds still. A trader new to reading chains often assumes it should — after all, isn't implied volatility a property of the stock? It isn't. Implied volatility is the number you get when you take an option's actual market price and back-solve the Black-Scholes formula for the one input nobody can observe directly: how much the market expects the underlying to move. Every strike and every expiration has its own market price, so every strike and every expiration gets its own IV. A single stock can show a dozen different IV readings on the same chain at the same moment, and all of them are correct.
The column is a slice of the smile
Plot IV against strike for a single expiration and the points rarely form a flat line. On most single-name equities the curve looks like a lopsided smile: IV is lowest somewhere near the money and rises as strikes move further out on either wing, with the downside wing usually rising faster than the upside one. That shape has a name — volatility skew — and it's the reason the IV column you're scanning down the chain isn't noise. It's one vertical slice through that curve, strike by strike, rendered as a list of numbers instead of a chart.
You can see the same shape rendered as an actual surface — strike, days to expiry, and IV all plotted together — in OptionScope's Greeks Lab, where the 3D volatility surface makes the smile something you rotate and look at instead of something you have to reconstruct in your head from a column of percentages.
Why the wings price richer than the middle
Three forces build that shape. First, crash risk is asymmetric — equities gap down far more violently than they gap up, so market makers charge more to sell downside protection, lifting OTM put IV. Second, there's a mechanical link between price and volatility in equities: as a stock falls, its financial leverage rises, which tends to make it more volatile, so the market prices that relationship in ahead of time. Third, one-sided hedging flow matters — a large base of investors buying downside puts for protection, and index funds and market makers hedging that flow, pushes put-side IV higher independent of any crash-risk story at all. None of this is visible from a single IV reading; it only shows up once you compare IV across strikes.
What "the stock's IV" actually means
So when a headline or a scanner says a stock's "IV" is 42%, what number is that actually referencing? Almost always it's the at-the-money IV for a specific expiration — usually the front month, or whichever expiration the tool defaults to. That single figure is a convenient shorthand, and it's what feeds IV rank and IV percentile calculations, because ATM options are the most liquid, most heavily traded, and least distorted by skew of any strike on the chain. It's a real and useful number — it's just a single point sampled off a curve, not a description of the whole chain.
The shape changes across expirations too
Skew is the strike-axis version of this. There's a second axis worth reading: how ATM IV itself changes as you move from the front-month expiration out to further-dated ones — the IV term structure. Combine the two and the full picture is really a surface, not a line: IV varying by both strike and time simultaneously, which is exactly what a chain with multiple expiration tabs is quietly encoding, one column at a time.
Why this changes how you pick a strike
The practical consequence shows up the moment you're comparing two strikes for a credit spread. Moving further out of the money doesn't just reduce your premium linearly because you're further from spot — it also runs into rising IV, which partially offsets the drop in premium you'd otherwise expect. That's part of why a strike 10% out on the put side rarely collects "10% less" credit than one 5% out; skew is quietly working against the simple distance math. Reading the IV column across a row of strikes, rather than glancing at one, is what catches that before it costs you basis points on the fill.
For the fundamentals behind implied volatility itself, start with the implied volatility guide in the Learn hub, or the broader column-by-column chain guide this post builds on.