On Sunday 1 Feb 2026, Budget Day, Nifty closed at 24,825.45. Two calls for the 10 Feb expiry settled that day: the 25,100 call at Rs 146.00 and the 25,600 call at Rs 42.60. On Monday Nifty rose 1.06% to 25,088.40. The 25,100 call settled at Rs 205.10, up 40.5%. The 25,600 call settled at Rs 41.90. The index went up and the premium went down. If you have ever asked why your call did not rise when the Nifty did, this is the answer. The index is one of five things that move the price, and on that Monday it was not the strongest.
3By the end you can
- Name the five things that move an option's price and say which are tiny for a weekly Nifty option.
- Explain how a call can fall on a day the index rises.
- Say where implied volatility comes from and why nobody observes it.
The idea, plainly
An option price is intrinsic value plus time value, as module F14 showed. Five things push it around. I call them the dials. The strike is not one of them. It is fixed in the contract, and the dials are measured against it.
- The level of the index. Calls rise with the index and puts fall. How much depends on the strike. The 25,100 call moves about 34 rupees for every 100 points of index. The 25,600 call moves only 13. That rate is the delta, in module F21.
- Time left. Every calendar day takes time value away, index or no index. One day costs the 25,100 call about Rs 13.31 and the 25,600 call about Rs 7.81. That is theta, in module F22.
- Implied volatility. How far the market expects the index to move. One point of it is worth about Rs 14.26 on the 25,100 call and Rs 8.18 on the 25,600 call. Nobody observes it. It is solved backwards from the price, as module F23 explains.
- The interest rate. Small over a week. A higher rate lifts the future, which lifts calls and trims puts. One percentage point was worth about Rs 2 on the 25,100 call, against Rs 14.26 for one point of volatility.
- Dividends. The index shares pay them, and the future is priced lower by what falls due before expiry. Rate and dividends meet in the gap between the future and the spot, the carry. On 2 Feb the March future stood 209 points above the spot.
A call gains as the index rises and loses as the days pass
Read 2 more paragraphs, 72 words
Three of the five do most of the work in a weekly option: the index, time and volatility. Rate and dividends are small over days and grow with the months left. The dials also move together, and the market shows only their sum.
Read the list against the story. On Monday the index dial pushed the 25,600 call up. The time dial and the volatility dial pushed it down, and they won.
Why a far option feels the index so little
Delta is also a rough odds meter. The 25,100 call had a delta of 0.34 and the 25,600 call 0.13. The market saw the far strike as much less likely to finish in the money, so a move in the index shifts its price only a little. A near option follows the index more closely. A far one waits for a big move and in the meantime pays for every day.
How an option price is calculated
No exchange formula sets the price. Buyers and sellers set it, in the order book. A model turns the five inputs into a fair price. This school uses Black 76, which prices a Nifty option off its forward. Traders also run a model backwards: they take the traded price and solve for the volatility that makes the model agree. That number is the IV. The IV column on a chain is the same idea, though sources differ a little in model and inputs. Module I04 builds the model step by step.
Worked example: Budget Day to Monday, 1 to 2 Feb 2026
We follow two calls for the 10 Feb expiry across one night. Prices are in rupees per unit. The middle row of the table asks what each call would have been worth if only the index and the clock had changed, with implied volatility held where it was on Sunday. It is a Black 76 estimate, not an NSE price.
The term this section turns on: Implied volatility
| What we read | 25,100 call | 25,600 call |
|---|---|---|
| Settle, Sunday 1 Feb | 146.00 | 42.60 |
| Implied volatility, Sunday | 16.8% | 17.2% |
| Estimate: index up 1.06%, one day gone, same volatility | 243.79 | 78.76 |
| Implied volatility, Monday | 14.2% | 13.6% |
| Settle, Monday 2 Feb | 205.10 | 41.90 |
| One lot of 65 units, Sunday to Monday | Rs 3,841.50 | −Rs 45.50 |
India VIX rose into the Budget and fell away once it had passed
One day on, the index move and the volatility move both change what a call is worth
| Index move | One day on, rupees | ||
|---|---|---|---|
| IV −3 | IV same | IV +3 | |
| −2% | −8,604 | −7,519 | −6,071 |
| −1% | −6,944 | −5,110 | −3,015 |
| 0% | −3,419 | −883 | +1,751 |
| +1% | +2,782 | +5,662 | +8,545 |
| +2% | +12,028 | +14,727 | +17,485 |
Green is profit and red is loss; deeper colour means a larger amount. The outlined cell is the starting point.
Read 3 more paragraphs, 146 words
The index and the clock together would have lifted the 25,600 call to Rs 78.76. Then implied volatility fell 3.7 points and took Rs 36.86 back. The 25,100 call lost a similar Rs 38.69 to the volatility drop, but its gain from the index was bigger, so it still ended 40.5% higher.
Why did volatility fall? India VIX, the market's own measure of expected volatility, rose into the Budget and fell away once it was past. An event that is still ahead is priced into the options. When it passes, that part of the price leaves.
One example proves little, so here is the whole grid. Each cell is the profit or loss, in rupees, on one lot of the 25,100 call bought at Rs 146.00 on Sunday, one day later, for a given move of the index and a given shift in implied volatility.
The common mistake
The belief: If the Nifty goes up, my call has to go up.
It treats one dial as the whole instrument. On Monday 2 Feb 2026 the index rose 1.06% and the 25,600 call fell from Rs 42.60 to Rs 41.90. A call far from the index has a small delta, so it feels a rise only a little. It also pays for a day of time and, here, for a drop in implied volatility. Before you blame the market, ask what else changed. Check the days left, the implied volatility and how far the strike sits from the index. Each is a dial, and the index is only the loudest.
Key takeaways
- Five dials move an option price: index, time, volatility, interest rate, dividends.
- The strike is fixed. The dials are measured against it.
- A far out of the money call barely feels an index rise.
- Implied volatility is solved backwards from the price, not observed.
- Time takes value every calendar day, index or no index.
- A rise in the index can come with a fall in the premium.
Before you trade. Derivatives trading carries a high risk of loss. SEBI's study "Profitability of Individual Traders in the Equity Derivatives Segment (FY25 to FY26)" (August 2026) found that 87.7% of individual traders in equity F&O made net losses in FY26, with aggregate net losses of Rs 91,685 crore. Read the SEBI study