Option Premium: What You Pay and Why It Moves

Key Takeaways

• Option premium equals intrinsic value plus time value; a $2.75 quote costs $275 per contract after the 100-share multiplier.
• Of the six Black-Scholes inputs, implied volatility is the only one estimated, it is the single biggest day-to-day swing factor in premium.
• Comparing premiums across strikes without moneyness context is misleading: a $0.25 deep-OTM weekly is almost certainly going to zero regardless of its small dollar cost.
• Premium decays every calendar day even when the underlying is flat because time value erodes (theta), independent of any price move.

What It Is

Every option has a quoted bid (what the market is willing to pay) and an ask (what the market is willing to sell for). The midpoint is a reasonable estimate of fair value, but the actual execution price depends on which side of the spread you cross.

The quoted number is per share of the underlying. For US listed equity options, each contract covers 100 shares, so the dollar cost is the quote times 100. A call quoted at $2.75 costs $275 per contract plus commission.

Premium has two components that sum to the total:

premium = intrinsic value + time value

Intrinsic value is what the option is worth if exercised right now. Time value is everything else.

The Intuition

Why does anyone pay a premium? Because an option gives you a payoff with a different shape than holding the underlying. For a fixed known cost, a call buyer gets unlimited upside and capped downside. A put buyer gets protection against a decline. Those asymmetric payoffs have economic value, and the premium is the market's price for that value.

The premium is higher when more can happen before expiration. Longer time, higher volatility, and strikes closer to the current price all raise the cost. Shorter time, calmer markets, and strikes far from the current price lower it.

Sellers of options get the mirror view. They collect the premium up front and keep it if the option expires worthless. In exchange, they accept an asymmetric downside that can be much larger than what they received.

How It Works

The Black-Scholes model, published by Fischer Black and Myron Scholes in 1973 in the Journal of Political Economy, formalised how six inputs drive the premium of a European-style option on a non-dividend-paying stock. Subsequent extensions, including Merton's work the same year, generalised the framework to dividends and other asset classes. The six drivers are:

1. Underlying price (S). For a call, higher S raises the premium. For a put, higher S lowers it.
2. Strike price (K). For a call, higher K lowers the premium. For a put, higher K raises it.
3. Time to expiration (T). More time raises premium for both calls and puts because the underlying has more room to move.
4. Volatility (sigma). Higher volatility raises the premium for both calls and puts. This is implied volatility when the premium is given and we solve for sigma.
5. Risk-free rate (r). Higher rates slightly raise call premiums and lower put premiums.
6. Dividends. Expected dividends reduce call premiums and raise put premiums, because dividends push the ex-dividend stock price down.

In practice, traders treat the strike and expiration as fixed for a given contract, and watch the underlying price, volatility, and time decay as the premium moves through the day.

Worked Example

AAPL is trading at $180. You look at two calls expiring in 30 days.

• AAPL 180 call (ATM). Premium quoted $3.50. Intrinsic value is zero. All $3.50 is time value. Cost per contract: $350.
• AAPL 170 call (ITM by $10). Premium quoted $11.20. Intrinsic value is $10.00. Time value is $1.20. Cost per contract: $1,120.

Notice the ATM call has more time value than the ITM call, even though its total premium is much lower. This is because time value peaks around the strike, where uncertainty about the final outcome is highest.

If implied volatility jumps from 25% to 35% while the stock stays at $180, both premiums rise because the market now expects a wider distribution of possible final prices. The ATM call might rise to $4.90 and the ITM call to $12.30, even with no change in the underlying. That is volatility risk baked directly into the premium.

Common Mistakes

1. Confusing premium with total cost. A quote of $1.50 on a US equity option is $150 per contract, not $1.50. Beginners who skip the multiplier size positions wrong by two orders of magnitude.

2. Comparing premiums across strikes without moneyness context. A $0.25 premium sounds cheap, but if it is deep OTM with two days to expiration, it is also almost certainly going to zero. A $12.00 premium sounds expensive, but if it is mostly intrinsic value, it behaves like owning the stock at a discount to the strike.

3. Ignoring the bid-ask spread. Illiquid strikes can have spreads of 10 to 20 percent of the mid price. Paying the ask and later selling at the bid eats a meaningful share of the trade's expected P&L. Always check the spread before trading, and use limit orders rather than market orders on thin strikes.

4. Assuming premium moves only with the underlying. Premium shrinks each day even if the underlying is flat, because time value decays (theta). Volatility can also move premium without any underlying move at all. A long option position can lose money on a calm day simply because time passed and implied volatility slipped.

Frequently Asked Questions

Q: What is option premium in simple terms? Premium is the price you pay to own the option. It is quoted per share, but each US equity option covers 100 shares, so multiply the quote by 100 for the actual dollar cost.

Q: How does understanding option premium affect investment decisions? Knowing that premium has intrinsic and time value components helps you compare options rationally. A deep ITM option with most value in intrinsic behaves very differently from an ATM option that is all time value.

Q: What is a real-world example of premium changing? An ATM AAPL call at $3.50 can rise to $4.90 if implied volatility jumps from 25 to 35 percent, even with the stock flat. That is a 40% premium increase with zero directional move.

Q: How can investors avoid overpaying for premium? Always check the bid-ask spread before trading. Illiquid strikes can have spreads of 10–20% of mid-price. Use limit orders near the midpoint rather than market orders on thin strikes.

Q: How is option premium different from intrinsic value? Intrinsic value is the immediate exercise profit; premium includes intrinsic plus time value. In practice, premium is always at least equal to intrinsic value, any gap would allow riskless arbitrage.

Sources

1. Cboe Options Institute. "Options 101." https://www.cboe.com/optionsinstitute/options_basics/options_101/
2. Options Clearing Corporation. "Characteristics and Risks of Standardized Options (June 2024 ODD)." https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
3. Black, F. and Scholes, M. (1973). "The Pricing of Options and Corporate Liabilities." Journal of Political Economy, 81(3), 637-654. https://www.cs.princeton.edu/courses/archive/fall09/cos323/papers/black_scholes73.pdf
4. OCC Options Industry Council. "Theta." https://www.optionseducation.org/advancedconcepts/theta

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.