India VIX is one number, quoted in percent, that summarises how much movement the Nifty options market expects over the next 30 calendar days. A reading of 15 means "about 15% a year" in volatility terms, which works out to roughly 0.79% for a single day.
I look at it every day, so I wanted to go back to NSE's own documents and write down what it actually is, step by step, before saying anything about how to use it.
What India VIX measures
NSE describes the Volatility Index as "a measure of market's expectation of volatility over the near term." The amount by which the Nifty is expected to fluctuate over that near term is calculated as an annualised volatility, written as a percentage, for example 20%.
Three words in that description matter:
- Expectation. It is not measured from past price moves. It comes from the prices people are quoting for Nifty options right now, so it reflects what the market is pricing, which is why it is called implied volatility.
- Volatility. It describes the size of movement, up or down. A VIX reading carries no direction.
- Annualised. The figure is scaled to a one-year basis, even though it describes the next 30 days. That scaling is what you have to undo when you want a daily number.
How NSE computes it
NSE publishes two documents on this: a white paper and a computation methodology. Here is what they say, in plain terms.
Input: the option order book. NSE says that from the best bid-ask prices of Nifty options contracts, a volatility figure is calculated which indicates expected market volatility over the next 30 calendar days. The inputs are the best bid and ask quotes of out-of-the-money options, in the near and the mid (next) month expiry, traded on the NSE F&O segment. These are quotes sitting in the order book, not only prices of trades that happened.
Which options count as out of the money. NSE identifies them using a forward index level, and the forward level is taken as the latest available price of the Nifty future.
Interest rate. The NSE MIBOR rate for the relevant tenure (30 days or 90 days) is used as the risk-free rate.
Two months, one 30-day number. The variance for the near and the mid month are computed separately, then interpolated to get a single variance with a constant maturity of 30 days. That is how a figure from two options expiries, which keep ageing, becomes a number that always describes "the next 30 days."
Time in minutes. Time to expiry is computed in minutes rather than days, for precision. NSE's white paper uses a year of 525,600 minutes, which is 365 calendar days of 1,440 minutes.
Final step. The square root of the variance is multiplied by 100, and that is the India VIX value.
Method. NSE says India VIX uses the computation methodology of CBOE, with suitable amendments to adapt to the Nifty options order book using cubic splines and similar techniques.
| Piece | What NSE uses |
|---|---|
| Instruments | Out-of-the-money Nifty options, near and next month |
| Prices | Best bid and ask quotes from the order book |
| Forward level | Latest Nifty futures price |
| Interest rate | NSE MIBOR (30-day or 90-day) |
| Horizon | Constant 30 calendar days |
| Time clock | Minutes, 525,600 a year |
| Output | Annualised volatility, in % |
I haven't tried to reproduce the full calculation myself. The documents give the steps, but I would not claim a result I haven't checked.
Turning VIX into a one-day move: a worked example
This is the part people most often ask for. The logic has two steps.
- VIX is quoted per year. Volatility scales with the square root of time, so you divide by the square root of the number of days in a year to get one day.
- Multiply the percentage by the index level to turn it into points.
Which number of days? NSE's own clock is 365 calendar days (525,600 minutes), so VIX ÷ √365 matches the way the index is built. Many traders prefer √252, counting only trading days. Both appear in practice, so I show both.
Illustrative numbers only. I picked a round VIX of 15 and a round index level of 20,000. They are made up to show the arithmetic; they are not today's figures, and nothing here is a forecast.
| Step | Calendar-day basis | Trading-day basis |
|---|---|---|
| Days in a year | 365 | 252 |
| Square root | 19.105 | 15.875 |
| VIX ÷ square root | 15 ÷ 19.105 = 0.785% | 15 ÷ 15.875 = 0.945% |
| × index level of 20,000 | about 157 points | about 189 points |
So with those made-up inputs, a VIX of 15 corresponds to a one-standard-deviation daily move of about 0.79% (roughly 157 points) on NSE's calendar clock, or about 0.94% (roughly 189 points) on the trading-day convention.
The same method works for other horizons. Over 30 days, which is what VIX actually describes, you scale by the square root of 30 ÷ 365, which is about 0.287. That gives 15 × 0.287 = about 4.3%, or about 860 points on the same made-up 20,000.
What "one standard deviation" means: if daily changes followed a bell curve and the VIX were exactly right, about two days in three would fall inside that range and one in three outside it. Real markets have fatter tails, and VIX is a price, not a guarantee, so treat the result as a ruler for scale. I tested how well this ruler fit 96 sessions of Nifty data in a separate post on the Nifty's daily range and VIX, so I won't repeat those numbers here.
What a VIX number can and cannot tell you
What it can tell you
- How expensive Nifty options are relative to other days. Higher VIX means option buyers are paying more for protection or exposure.
- The rough scale of movement the market is pricing, using the arithmetic above.
- How the mood has changed. A figure that has moved up or down over a few days shows a change in what is priced.
What it cannot tell you
- Direction. The calculation uses both calls and puts. It has no up or down in it.
- Timing. It is a 30-day blend, so it cannot say which day will be the quiet one and which the busy one.
- What will happen. It is what people are quoting today. The index can then move much more or much less than the ruler suggests.
Expiry days are a good example of why a daily conversion is rough. The way the weekly contract rolls and settles changes behaviour late in the day, which I wrote about in what changes on expiry days. A flat 30-day number spread evenly over days does not capture that.
Reading it next to other pre-market information
I use India VIX as one of several inputs when I write my notes each day. It gives a sense of scale. GIFT Nifty describes where the market may open, and the pre-open session shows how the opening price is discovered. None of the three says which way the day goes. That is consistent with what I found when I checked whether the pre-market read predicts anything.
As a plain fact for today: India VIX closed at about 14.5 on 1 October 2026, after about 13.5 the previous day (Zerodha Kite data). I mention it only so you can see what a reading looks like. The arithmetic above is separate and uses made-up numbers.
Limitations of this guide
- I relied on NSE's published documents, and the sources listed below. NSE may revise its methodology, so check the current documents.
- The explanations here are in plain language, so some detail is left out, such as how strikes are selected and how the variance formula is built from option prices.
- The daily conversion assumes volatility is spread evenly across days. It is a rule of thumb.
What I take from it
India VIX is a price for movement, quoted as an annual percentage and built from Nifty option quotes for the next 30 days. Dividing by √365 (or √252) turns it into a rough daily scale. It is useful for knowing how large a normal swing is, and it is not a tool for knowing which way the market goes.
Sources
- NSE: India VIX index page (volatility index as a measure of market's expectation of volatility over the near term; annualised percentage; best bid-ask prices of Nifty options; next 30 calendar days; CBOE methodology adapted with cubic splines)
- NSE: India VIX computation methodology (near and mid-month out-of-the-money Nifty options; forward level from Nifty futures; NSE MIBOR; interpolation to a constant 30-day maturity; time in minutes; square root of variance times 100)
- NSE: India VIX white paper (annualised percentage; 525,600 minutes in a year)
- India VIX closing values for 30 September and 1 October 2026: Zerodha Kite quote data.
- Worked example: my own arithmetic using made-up inputs (VIX 15, index 20,000), for illustration only.
This guide is for information only. It is not investment advice or a recommendation to trade. Past patterns say nothing certain about the future. I am not registered with SEBI as an investment adviser or research analyst.