An options chain is a list of different contracts, not a list of interchangeable ways to buy the same stock. Each row changes the price you may transact at, the time available, or the payoff itself.
Before comparing premiums, identify the underlying, expiry, strike, call or put, contract multiplier, and settlement terms. A low displayed premium is not meaningful until you know what one contract buys.
From a quote to a dollar cost
A call gives its holder a right to buy at the strike under the contract's terms; a put gives a right to sell. A standard U.S. equity option usually represents 100 shares, although adjusted contracts can differ. The Options Industry Council's options basics describes these rights.
Suppose a $50-strike call is quoted at a $2.00 bid and $2.20 ask. Buying one standard contract at the ask costs $220. Selling immediately at the unchanged bid receives $200, a $20 difference before commissions. The last trade or midpoint is useful context, but neither is a promise of an available fill.
Check displayed size as well as price. A narrow spread for one contract may not describe the cost of trading 50. Open interest counts outstanding contracts; it does not guarantee someone is currently willing to take the other side at a good price.
Intrinsic value and time value
If the stock is $51, the $50 call has $1 per share of intrinsic value: exercising permits purchase at $50 of something worth $51. The remaining $1.20 of the $2.20 premium reflects the value of possibilities before expiry, alongside other pricing inputs.
At expiration, with the stock at $54, the call is worth $4 per share. The $400 payoff minus the $220 premium produces a $180 profit before costs. Its expiration breakeven is $52.20.
That breakeven is not a price the stock must reach for the option to be profitable before expiration. The option may appreciate earlier because time remains or expected volatility rises. It may also lose value despite a favorable stock move if other pricing inputs change enough.
Local sensitivities: the Greeks
Delta estimates sensitivity to a small move in the underlying. A delta of 0.55 suggests roughly a $55 change in one standard contract for a $1 stock move, holding other inputs fixed. Gamma describes how that delta changes; the first estimate becomes less reliable over a large move.
Theta describes sensitivity to passing time, and vega to changes in implied volatility. If vega is quoted as $0.08 per share for a one-percentage-point volatility change, a five-point decline implies roughly a $40 loss on a 100-share contract, all else equal. Verify the platform's units. The OIC's guide to Greeks explains that these are model-based sensitivities, not guaranteed P&L.
Implied volatility is inferred from the option's price. A high figure says optionality is expensive under the model's assumptions; it does not establish that buying it is a good trade. An anticipated announcement can already be priced into the premium.
The seller’s obligation
Buying a standard option and writing one create different obligations. A short $50 put can require buying 100 shares for $5,000 if assigned. If the shares then trade at $47, that position has a $300 intrinsic loss before accounting for the premium received. The required purchase cash is still $5,000.
American-style options can be exercised before expiry. Assignment, broker cutoffs, and the treatment of an option near the strike require attention; one leg of a spread does not automatically guarantee that every other leg is handled as intended. See the OIC's exercise and assignment explanation.
What the cheap-looking premium leaves out
Our $2.20 call costs $220, initially responds to a small stock move like roughly 55 shares, and can lose value if implied volatility falls. Those are three different descriptions of the same position. Whether it suits the idea depends on when the expected move occurs and which of those effects dominates before the exit.