Realized vs Implied Volatility (the IV–RV Gap)

Implied volatility (IV) is what the options market expects the underlying to move going forward; realized volatility (RV) is how much it actually moved. Comparing the two is one of the cleanest reads on whether options are rich or cheap. Unusual Whales reports both on its realized-volatility endpoint and deliberately aligns them in time so you can see whether the market has been over- or under-pricing risk.

Realized (historical) volatility

Realized volatility, also called historical volatility, is the annualized standard deviation of the underlying's actual returns over a recent window. UW defines its realized series as "the realized/historical volatility of a stock's price over the past 30 days (21 trading days)." It is backward-looking and model-free — just the statistics of what the stock did. A stock that chopped in a tight range has low RV; one that gapped and trended has high RV. RV is the benchmark against which the option market's forecast (IV) gets graded.

Implied volatility, recapped

IV is the forward-looking volatility backed out of current option prices. UW frames its implied series as "the expected 30 day forward looking volatility." Because IV is set by supply and demand for options, it embeds a risk premium: option sellers typically demand more than the eventually-realized move to compensate for the open-ended risk they take. That structural tendency for IV to sit above subsequent RV is the volatility risk premium, and it is why systematically selling options has an edge on average (paid for by occasional large losses).

The IV–RV gap as a richness/cheapness signal

The gap between IV and RV is the core signal. When IV is well above RV, options are "rich" — the market is charging more for the expected move than the stock has been delivering, which favors premium-selling strategies (and warns option buyers they are overpaying). When IV is below RV, options are "cheap" — the market is under-pricing how much the stock actually moves, favoring premium buyers and long-gamma structures. The ratio IV/RV is a quick gauge: persistently above 1 means a fat volatility risk premium; below 1 is unusual and often precedes an IV expansion.

UW's time-alignment method (the 30-day backshift)

A naive IV-vs-RV comparison is apples-to-oranges: today's IV forecasts the next 30 days, while today's RV summarizes the past 30 days. UW corrects this. In its own words: "Since IV is forward looking, the realized volatility is shifted 30 days backwards to see if the past IV pricings were frequently underpricing or overpricing the realized volatility risk." In other words UW lines up each IV reading with the realized volatility of the period that IV was actually predicting, so you can fairly judge whether the market's forecasts came true. This backshift is what turns the comparison into a real forecast-accuracy scorecard rather than a coincidental overlay.

How to read it

If the aligned series shows IV consistently sitting above the RV it predicted, the name carries a healthy volatility risk premium and option sellers have been rewarded — but stay alert, because the premium exists precisely to pay for the rare large move. If IV has been below the RV it predicted, buyers of that name's options have been getting a bargain and the market has been underpricing risk. Always read the gap in context: around known catalysts (earnings, FDA dates, macro prints) IV legitimately rises ahead of an expected jump, so a wide IV–RV gap there reflects an event, not necessarily mispricing.

Common mistakes

Comparing raw forward IV against trailing RV without aligning the windows overstates or understates the premium — UW's backshift is there specifically to avoid this. Assuming a high IV–RV gap is "free money" for sellers ignores that the premium compensates for tail risk; one outsized move can erase many premium-selling wins. And treating low RV as a reason to buy options forgets that low realized volatility can persist far longer than a long-premium position can survive theta decay. Use the IV–RV relationship together with IV Rank/percentile (see that note) to decide whether the volatility being priced is genuinely cheap or expensive.