Lessons › Advanced track › Options: time decay and implied volatility

World 10 · Advanced track · lesson 9 · level 5

Options: time decay and implied volatility

An option is like melting ice: it loses value as time passes, and its price also changes with how wild people expect the market to be.

In one line

You bought a call, the stock went up, and the call still lost value. What melted?

Explained simply

An option's price has two parts, like an ice cream with a cone and a scoop. The cone is the real value you would get by using the option now, and the scoop is extra 'maybe' value that melts as expiry gets closer, faster and faster near the end. When a big event passes and the 'maybe' disappears, much of the scoop can melt at once.

The lesson

An option's premium is intrinsic value plus time value; time value shrinks as expiry approaches, fastest near the end, which is called theta decay, and at expiry an option is worth only its intrinsic value. Implied volatility (IV) reflects how big a move the market expects, so options often get more expensive before big events and cheaper right after, which traders call IV crush. Delta estimates how much an option's price moves for a 1-point move in the underlying: about 0.5 for an at-the-money call and close to 1 for a deep in-the-money call. This is why many option buyers lose even when they pick the right direction: the move must be big enough and soon enough to beat the time value and any IV drop they paid for.

A worked example

Illustrative example with modeled prices: a stock is at 100 the day before its results. A 100-strike call with 14 days left costs 6.00, all of it time value, because its intrinsic value is 0. The stock jumps to 104, but implied volatility collapses, and the call is now worth 5.00: intrinsic value 104 - 100 = 4 and time value 5.00 - 4 = 1.00. The buyer was right about the direction but lost 6.00 - 5.00 = 1.00 per share, or 1.00 x 100 = 100 dollars per contract. With a delta of about 0.5, the 4-point rise alone would have added roughly 0.5 x 4 = 2.00, but the drop in implied volatility and a day of time decay took away more.

The same idea at four levels

1. Beginner. An option's price is its real value now (intrinsic value) plus extra 'maybe' value (time value).
2. Foundation. Time value melts as expiry nears, faster in the last weeks, and that melting is called theta decay.
3. Intermediate. Implied volatility is the market's guess of how big moves will be, and higher IV means pricier options.
4. Advanced. Before scheduled events IV usually rises and afterwards it often drops sharply, so a buyer can be right on direction and still lose if the IV crush and time decay outweigh the move.
5. Expert. Delta links price moves to option moves, about 0.5 at the money and near 1 deep in the money, and since SEBI found 87.7% of individual options traders in India lost money in FY26, a buyer should size for losing the whole premium.

Mistakes to avoid

• Buying options before an event and being surprised when they lose value despite the right direction.
• Holding out-of-the-money options into the last days, when time decay is fastest.
• Judging whether an option is cheap or expensive without looking at its implied volatility.

Goal of this lesson: Understand how time decay, implied volatility and delta change an option's price.