Call Option

A call option is a contract that gives the buyer the right, but not the obligation, to buy an underlying asset, such as an index or a stock, at a fixed price on the expiry date. The buyer pays a premium for that right. The seller of the call collects the premium and takes on the obligation to sell at that price if the buyer exercises.

Call buyer: right to buy at the strike price. Call seller: obligation to sell at the strike price.

A call gains value when the price of the underlying rises, which is why traders buy calls when they expect a rise.

How a call option works

Every call option is defined by four things:

• Strike price: the price at which the buyer can buy.
• Premium: what the buyer pays and the seller receives, quoted per unit.
• Expiry date: the day the contract settles. Options on NSE and BSE are European style, so they can only be exercised at expiry, not before. You can still sell your call at any time before then.
• Lot size: the number of units in one contract, set by the exchange for each underlying.

At expiry, a call is worth the underlying price minus the strike price, or nothing if the underlying is at or below the strike. That’s its intrinsic value. Index calls are cash-settled. Stock calls are physically settled: an in-the-money stock call held to expiry means you have to buy the shares at the strike price.

Call option example: buying an index call

Say an index is at 20,000 and you expect it to rise. You buy one lot of the 20,100 call at a premium of ₹100, with a lot size of 50 (hypothetical numbers).

• Premium paid: ₹100 × 50 = ₹5,000. This is the most you can lose.
• Breakeven: strike plus premium = 20,100 + 100 = 20,200.

The loss is capped at the premium however far the index falls. Above the breakeven, every 1-point rise adds ₹50 to your profit, and there’s no upper limit. Notice that the index can rise from 20,000 to 20,150 and you still lose money: the call has to finish in the money by more than the premium you paid before you profit.

Buying vs selling a call option

Call sellers are betting the underlying stays below the strike. When many traders sell calls at the same strike, that strike is often read as resistance, and a large concentration of call open interest there is called an OI wall. Fresh call writing shows up as short buildup in calls, which is bearish to neutral for the underlying. Selling calls without a hedge is a naked option position, with no limit on the loss in a sharp rally.

Call option vs put option

With the index at 20,000, a 19,900 call is in the money and a 20,100 call is out of the money. For puts, it’s the other way round.

When traders use call options

• A bullish trade with limited risk. Buying a call lets you profit from a rise while risking only the premium.
• Less capital than futures. In the example above, one lot of futures would have a contract value of 20,000 × 50 = ₹10,00,000 and need margin, while the call costs ₹5,000. The trade-off is that the call loses value over time and needs the move to happen before expiry.
• Hedging a short position. If you’re short one lot of futures at 20,000 and buy the 20,100 call at ₹100, your worst case is (20,100 – 20,000 + 100) × 50 = ₹10,000, however high the index goes. That’s hedging with a call.
• Cheaper bullish trades. A bull call spread buys one call and sells a higher-strike call, cutting the cost in exchange for a capped profit.
• Earning income on shares you own. Selling calls against shares you hold is a covered call: you collect premium but give up gains above the strike.

What moves a call option’s price

• The underlying. A call gains when the underlying rises and loses when it falls. Delta shows by how much.
• Time. A call’s time value shrinks every day because of theta, and the decay speeds up close to expiry.
• Volatility. Higher implied volatility makes calls more expensive. When IV drops after an event, premiums can fall even if the price holds, which is volatility crush.

Common mistakes with call options

• Buying far out-of-the-money calls because they’re cheap. They need a big move to pay off, and most expire worthless.
• Ignoring the breakeven. Being right that the price will rise isn’t enough. It has to rise past the strike plus the premium before expiry.
• Buying right before an event. IV is usually high before results or policy announcements and falls afterwards, which can sink the premium even when the move goes your way.
• Forgetting delivery on stock calls. An in-the-money stock option held to expiry means paying for the full lot of shares.
• Chasing a rally. Buying calls after a sharp move often means paying an inflated premium with little room left. See FOMO trading.

To see live call premiums and open interest across strikes, open Stolo’s Nifty option chain, or check delta, theta and vega for every strike with Stolo’s Option Greeks tool.