Strike Price
The strike price (exercise price) is the pre-agreed price at which an option buyer can buy (call) or sell (put) the underlying asset. Strike selection — ATM, ITM, or OTM — fundamentally determines the option's probability of profit, premium cost, and leverage profile.
Definition
The strike price (also called the exercise price) is the contractually fixed price at which the buyer of an option has the right to buy (call) or sell (put) the underlying asset upon exercise. The strike is set at contract inception and does not change during the option's life — regardless of how the underlying moves. Exchanges list a ladder of strike prices at regular intervals around the current spot price. For Nifty 50 options, NSE lists strikes at 50-point intervals (e.g., 24,000, 24,050, 24,100…), with a wide range of strikes typically available: spot −/+ 10–12% in weekly contracts, and a wider range for monthly contracts. Source: NSE — F&O Master Circular.
ATM / ITM / OTM Classification
The moneyness of an option describes its current relationship to spot:
- At-the-money (ATM): Strike ≈ spot price. Highest time value; delta ≈ ±0.50. Premium is entirely time value (zero intrinsic value at exact ATM). Theta decay accelerates most sharply for ATM options near expiry.
- In-the-money (ITM): For a call, strike < spot (call has intrinsic value). For a put, strike > spot. Higher premium; delta approaches ±1 for deep ITM; behaves increasingly like the underlying itself.
- Out-of-the-money (OTM): For a call, strike > spot (no intrinsic value yet). For a put, strike < spot. Low premium; low delta; requires a large move to generate profit. OTM options have a lower probability of expiring profitably but offer high leverage if that move occurs.
The strike interval (tick) is set by the exchange and varies by instrument: Nifty 50 = 50 points; Bank Nifty = 100 points (near-ATM); individual stocks = ₹2.50 to ₹50 depending on price range.
Market Mechanics
- Open interest by strike: Exchange-published OI data shows how many contracts are outstanding at each strike for each expiry. Heavy OI at specific strikes is used by analysts as a proxy for support/resistance levels (put OI = support; call OI = resistance).
- New strike listing: As the underlying moves, NSE automatically lists new strikes to maintain coverage around the current spot — this happens intra-day for volatile instruments.
- Deep-OTM illiquidity: Strikes far from spot have low OI and wide bid-ask spreads. Limit orders are essential; market orders at deep-OTM strikes can result in poor fills.
- Strike price and margin: For option sellers, margin requirement depends on strike moneyness — ATM/ITM writing requires higher margin (higher probability of being exercised against).
Risk Profile
Strike selection is the primary determinant of an option position's risk/reward profile:
- Buyers of deep-OTM options experience the highest frequency of total premium loss (100% of outlay) because the required underlying move rarely materialises within the contract period. SEBI's 2024 data identified OTM option buying as a key driver of retail losses.
- Buyers of deep-ITM options behave like stockholders with defined downside — but pay high premiums with correspondingly high absolute risk in rupee terms.
- Sellers of OTM options collect smaller premiums but have a higher probability of those contracts expiring worthless (keeping the full premium) — until a tail event moves the underlying past the strike, at which point losses can be multiples of the premium collected.
Worked Example
Nifty 50 is at 24,500 (spot). An option trader surveys three call strikes with 28 days to expiry:
| Strike | Type | Premium | Delta | Break-even |
|---|---|---|---|---|
| 24,000 | ITM call | ₹620 | 0.72 | 24,620 |
| 24,500 | ATM call | ₹280 | 0.50 | 24,780 |
| 25,000 | OTM call | ₹95 | 0.25 | 25,095 |
The ITM call requires ₹620 × 25 = ₹15,500 outlay; the OTM call only ₹2,375 — but the OTM call requires Nifty to rise 2.4% just to break even, vs 1.1% for the ATM. If Nifty rises 1.5% to 24,868, the ITM call profits ₹248 per unit; the ATM call ₹88 per unit; the OTM call likely still loses money (still below its 25,095 break-even).
Caveats
- Purchasing many OTM strikes with small outlay on each is a portfolio risk-management error, not a diversification strategy — correlated outcomes mean simultaneous total losses are highly probable.
- The "max pain" theory (strikes where option writers incur minimum losses) is a popular but not reliably predictive analytical tool; do not use it as the sole basis for strike selection.
- Strike prices are fixed but IV is not — buying a strike at high IV and selling at low IV produces losses even with a correct directional view.
See Also
Primary Source
NSE — Equity Derivatives F&O Master Circular; SEBI Study on F&O Retail Participation, July 2024
MintByte (ARN-314872 / APMI APRN-01658) provides this glossary for educational purposes only. Nothing here constitutes investment advice, a recommendation to buy or sell any security, or a guarantee of returns. Equity and derivatives trading involves risk of loss. Consult a SEBI-registered adviser before making investment decisions.