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What is theta, in simple terms?

Theta is how much an option's price melts each day, just from time passing. Buyers lose that melt. Sellers collect it.

Options guide · 5-minute read · Updated 2026-10-27

The short answer

Theta tells you roughly how much an option's price drops in one day if nothing else changes. It's usually shown as a negative number, like −0.03. That means the option loses about 3 cents a share, or $3 per contract, each day.

For a buyer, that's a cost. For a seller, it's the point. You sold the option, so every bit of value it loses is value you get to keep.

Why options melt

An option is a bet on what the stock might do before a date. The more time left, the more could happen, so the more the option is worth.

Each day that passes, there's less time for a big move. So the option is worth a little less. On the Expiration date, the time value is gone. Only the part that's already "in the money" is left, if any.

The melt speeds up near the end

Theta isn't steady. An option melts slowly when expiry is far away, and faster as it gets close.

A rough picture for an option worth $1.00 with 30 days left, if the stock sits still:

These are made-up, round numbers. Real options vary. The shape is the lesson: slow at first, fast near the end.

That's why many sellers pick expiries about 30 to 45 days out. It's a habit, not a rule.

One example (an illustration, not a trade idea)

A made-up stock, XYZ, trades at $50. You sell a 30-day $45 put for $1.00 and collect $100. Theta is about −0.02.

The catch

Theta is small and steady. Stock moves are big and sudden.

If XYZ drops $5, the put gains far more value than a few days of melt can take away. That's why theta isn't spare money. It's what you're paid for taking on the risk of a move.

In the wheel strategy, theta is the engine. The stock's moves are the brakes, and sometimes the crash.

How to use theta

• Look it up on your Options chain. Most brokers show it next to each option.
• Compare it with the premium. A theta of −0.02 on a $1.00 option means a slow, steady melt if nothing moves.
• Don't chase the fastest melt. Very short expiries melt fastest but leave almost no room if the stock moves.
• Remember it's a guess. Theta assumes nothing else changes. Real markets never sit still.

If your short option lost value while the stock didn't move, theta is why. See why an option loses value when the stock sits still.

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