What Is Theta? Time Decay Explained
What is theta in a structured warrant — the daily cost of time decay, why it accelerates near expiry, and how to account for it before opening a position.
By warrants.asia Editorial Team · Published July 21, 2026
What is theta?
Theta measures how much a warrant's price is expected to fall each day purely from the passage of time, holding the underlying price and implied volatility constant. It's usually expressed as a negative number for a long warrant position — a warrant priced at RM0.20 with a theta of -RM0.002 per day is expected to lose about RM0.002 of value overnight even if nothing else changes.
Every structured warrant has theta working against a long holder continuously, because a warrant's price is made up of intrinsic value (how far in-the-money it is) plus time value (everything else) — and time value only ever shrinks as expiry approaches, never grows on its own.
Why theta accelerates near expiry
Time decay is not linear — it accelerates as a warrant gets closer to its maturity date, especially for at-the-money warrants. A warrant with six months to expiry might lose a small, steady amount of time value each week; the same warrant with two weeks left can lose a comparable amount in just a day or two. This is the mechanical reason buying warrants very close to expiry is flagged as a common mistake.
Accounting for theta before trading
Because theta works against a long position every single day, a warrant needs the underlying to move favorably (or implied volatility to rise) by more than the cumulative theta cost just to break even over a holding period — simply being directionally right isn't always enough if the move takes too long to arrive. Traders comparing two warrants on the same underlying often weigh theta alongside gearing: a higher-theta warrant needs a faster move to pay off.
FAQ
What is theta in a structured warrant?
Theta is the amount a warrant's price is expected to fall each day purely from time passing, holding the underlying price and volatility constant — the daily cost of time decay.
Does theta stay the same throughout a warrant's life?
No — theta accelerates as a warrant approaches its maturity date, especially for at-the-money warrants, meaning the daily cost of holding the position grows larger the closer it gets to expiry.
Can a warrant lose money even if I'm right about direction?
Yes — if the underlying takes too long to move in your favor, accumulated theta decay can outweigh the gain from the directional move, resulting in a loss despite being right about the direction.
Key resources
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