What Is the VIX: Why 0DTE Premiums Get Expensive When the Fear Index Rises
The VIX is often called the fear index, but it is not a number made up from feelings: it is computed straight from SPX option prices, and it measures how much the market expects the S&P 500 to swing over the next 30 days. Once you can read it, it becomes obvious why 0DTE premiums are sometimes expensive and sometimes cheap.
What the VIX is, in one line
The VIX is the Cboe Volatility Index, nicknamed the fear index. It is not a survey — it is a single number computed directly from SPX option prices.
It measures what the market expects: how much the S&P 500 will move over the next 30 days, quoted as an annualized percentage — a VIX of 20 means the market expects about 20% annualized volatility.
The VIX only says how big the move might be, not whether it goes up or down. It usually rises when stocks fall, which is how it earned the fear-index nickname.
Its long-run average is about 19–20. The highest close on record is 82.69 (March 16, 2020); the lowest close is 9.14 (November 3, 2017).
How to read the number: a few dividing lines
Below 15: calm, and buying protection is cheap. 15–20: normal — the market spends most of its time in this range.
20–30: elevated — the market is starting to buy protection against a fall, and premiums get more expensive. Above 30: clearly stressed, usually seen during sharp selloffs.
Turn it into a move: divide the VIX by 3.46 and you get the expected move over the next 30 days — a VIX of 20 means about ±5.8%, a VIX of 30 about ±8.7%. Divide by 15.9 instead and you get one day: a VIX of 20 means about ±1.3% a day.
A recent example: 16.61 on Nov 4, 2026, then 28.18 on Nov 5 (up 11.57 points in one day as stocks sold off), then 25.64 on Nov 6 and 19.92 on Nov 9. Stocks bounced back, and the VIX came back down with them.
How the VIX relates to 0DTE premiums
The higher the VIX, the pricier option premiums are: buyers pay more, and sellers collect more premium — but the risk is bigger too. Do not stare only at the fatter premium.
The VIX covers the next 30 days, while a 0DTE only has today left: the VIX can only point roughly in a direction, it cannot price today's premium for you. What really sets today's premium is how many hours are left and how far the S&P 500 sits from the strike.
There is also a 1-day version, the VIX1D: on Nov 6, 2026 it reached 36.80, which implied a same-day S&P 500 move of about 2.3% — that number sits much closer to a 0DTE.
Do not rush to trade on the day the VIX spikes: premiums are rich, spreads are wide, and prices jump fast. Watch a day in the simulator first — practicing after the VIX settles is never too late.
How to practice with it in the simulator
This simulator does not show the VIX — check today's VIX in your market-data app or on the Cboe website before you place an order, then decide whether to practice buying or selling, at the money or out of the money.
Compare the same strike on two days: how much does the same call cost on a VIX 16 day versus a VIX 28 day? Place one 1-contract order on each day in the simulator and write the difference down.
On high-VIX days, practice the risk of selling for premium first: a fat premium is not free money — one extra 1% move in the S&P 500 can eat several days of premium.
Start with 1 contract and write your exit plan before you enter. The VIX is only background noise — what really decides your P&L is the strike, the size, and exit discipline.
This simulator uses real CBOE option chains delayed about 15 minutes, starts with $10,000 in virtual funds, charges $0.65 per contract per side in fees, and shows P&L net of fees; short-sale margin is a simplified simulated rule at 20% of the strike, not a real broker margin. The simulator is for practicing orders, discipline, and review. It is not investment advice and promises no returns.