Weekly Expiry

Quick answer: Weekly Expiry refers to index option contracts that expire within days rather than a month, carrying less total time value but much higher theta and gamma per day, which concentrates both decay and risk into a short window.

In simple words

A weekly option is a contract with only a few days of life left. Because it has so little time, it does not cost as much as a monthly option, and that low price attracts buyers. But the same short life means its value melts quickly day by day, and its price reacts violently to small moves in the index as the last day nears. The exchange decides which weekday these contracts expire and how many weekly series exist, and it changes those rules from time to time, so the current specification should be checked on the NSE website rather than assumed.

The two forces at expiry

Professional explanation

Less total time value but more decay per day

A weekly contract holds only a few days of extrinsic value, so in absolute rupees it is cheaper than a monthly. That is exactly what misleads people. Theta for an at-the-money option scales roughly as 1/√T, so a contract with three days left sheds value several times faster per day than one with thirty. The buyer pays little and loses it quickly; the seller collects little and must survive a market that can erase weeks of such collections in a single session. The small absolute premium hides a large per-day rate of change.

Why weekly implied volatility usually sits above the monthly

Short-dated variance is more uncertain per unit of time. A single news event, an RBI decision or a US print lands with full force on a three-day option and is diluted across thirty days for a monthly. The market prices that concentration by quoting a higher implied volatility on the near series. This is a structural feature of the term structure, not a mispricing to be harvested — the higher IV is compensation for the higher realised swings the short contract actually experiences.

Liquidity concentrates in the nearest expiry

Volume and open interest cluster in the contract closest to expiry, which tightens spreads at the at-the-money strikes and thins them in the far wings. That concentration makes the near weekly easy to trade at the money and treacherous in the tails, where a market maker may quote a wide spread precisely when a fast move has pushed a strike into the money. Liquidity you relied on can withdraw at the moment you most need to exit.

Where most Indian retail option losses occur

SEBI's studies of individual trader outcomes in equity derivatives report that a large majority lose money, and weekly index options are the instrument in which most of that activity, and most of those losses, take place. The reason follows from the Greeks: cheap-looking premiums, rapid decay and explosive gamma combine to make the weekly the most seductive and least forgiving contract on the board. The picture on this page — theta and gamma both turning near-vertical near expiry — is the weekly's entire life compressed into days.

Construction

1. Read the two panels: theta (rupees lost per day) and gamma both against days to expiry for the same at-the-money option.
2. Note that at 30–45 days both curves are shallow, and both turn steep in the final days.
3. Understand that a weekly contract lives entirely in the steep region of both curves.
4. Check the current expiry weekday and the set of instruments offering weekly expiry on the NSE website — the exchange revises them.

Market outlook

A trader may study weekly contracts when the interest is in short-horizon exposure — a defined-risk directional bet for a few days, or a short-premium position held into a near expiry. The condition that invalidates the appeal is a view that needs time to be right: a weekly gives a thesis almost no room, because decay and gamma both act fastest here. Nothing about a short-dated contract is direction-specific; it is the horizon, not the outlook, that defines the weekly.

Risk profile

Risk depends entirely on how the weekly is used, so this page is marked defined only in the narrow sense that a long weekly option, bought outright, has defined risk — the premium paid, which is the maximum a buyer can lose. A short weekly position is a different animal with undefined risk, treated on the theta-harvest and expiry-day pages. The defining hazard of the weekly is gamma: because it scales as 1/√T, a short-dated position's delta can flip from nearly flat to nearly one-for-one over a move the index makes in an ordinary hour.

Reward profile

For a buyer, the reward is leverage — a small premium controls a full lot, and a sharp move in the remaining days can multiply it. For a seller, the reward is rapid theta: the last days hold the steepest part of the decay curve, so a short position that is not run over collects extrinsic value quickly. In both cases the reward is inseparable from the mirror risk, because the same short T that speeds decay also magnifies gamma.

Margin requirement

A long weekly costs only its premium. A short weekly attracts SPAN plus exposure margin, and because gamma is high near expiry, intraday margin requirements can rise sharply as the underlying moves. Brokers and NSE revise margin rules and can raise them on expiry day; the number you posted in the morning may not hold in the afternoon. Confirm current margin policy with the broker and exchange.

Greeks exposure

Volatility impact

A rise in implied volatility lifts the price of a weekly, helping a holder and hurting a seller, but the effect is muted because vega is small at short tenors — a large IV move produces only a modest price change on a three-day option. Falling IV does the reverse. The more important point is that a weekly's higher quoted IV is compensation for the sharper realised swings short contracts actually see; it is not a discount or a premium to be captured for free. As expiry approaches, quoted IV becomes numerically unstable because the pricing model divides by the square root of a time that is going to zero.

Time decay

Theta is the weekly's defining feature. A short-dated at-the-money option sheds extrinsic value several times faster per day than a monthly, because per-day decay scales roughly as 1/√T. On the schematic this is the region where the theta curve steepens toward vertical. The seller's apparent advantage — quick, visible decay — is exactly matched by the gamma curve steepening beside it. The contract that decays most obligingly is the one that punishes a wrong price most brutally, and both happen in the same final days.

Practical examples

Lot sizes used above (NIFTY 75, BANKNIFTY 30) are those in force at the time of writing; NSE revises them periodically. Figures exclude brokerage, STT, exchange charges, stamp duty and GST, all of which materially affect small spreads.

Common mistakes

• Treating a low weekly premium as low risk: the small absolute price hides a per-day decay and a gamma that are both several times a monthly's, so a cheap-looking short can lose multiples of the credit in one move.
• Holding a long weekly through a flat session expecting a move 'soon': theta is steepest here, so a correct view that arrives a day late can still expire worthless.
• Selling weekly options for the fast decay without pricing the matching gamma, then discovering that one ordinary index move erases weeks of collected premium.
• Assuming the far-wing strike you sold will stay liquid: near expiry, market makers widen or withdraw quotes exactly when a fast move pushes that strike toward the money.
• Assuming a fixed weekly expiry weekday or a fixed number of weekly series: NSE and SEBI have changed both, and a position built on last quarter's schedule can be mistimed.
• Ignoring that intraday margin on a short weekly can rise during the day, forcing an exit at the worst possible price if the account is under-funded.

Advantages & disadvantages

Professional usage

Desks use short-dated contracts to hedge or express very short-horizon gamma and event exposure, and they do so inside a book that is delta-hedged continuously and margined across positions — the gamma that overwhelms a single retail short is, for them, one line in a risk report that is rebalanced through the day. A retail trader cannot replicate that continuous hedging or cross-margin, so the same weekly that a desk carries neutrally sits on a retail account as a raw, un-hedged exposure. The instrument is identical; the risk management around it is not.

Frequently asked questions

Voice search & related questions

Natural-language questions people ask about the Weekly Expiry.

Sources & references

• NSE — contract specifications and settlement
• SEBI — regulations and studies of individual trader outcomes
• Natenberg, Option Volatility and Pricing

Last reviewed 9 July 2026. Educational content only — not investment advice.