Daksh Analytics

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Theta decay calculator. What time costs an option.

Enter an option's details to see its Black-Scholes price, how much it loses each day, and what it would be worth as expiry gets closer. The boxes start with example numbers. Change them to yours.

Default 25,000. Allowed 1 to 1,000,000.

Default 25,000. Allowed 1 to 1,000,000.

Default 7. Allowed 0 to 365.

Default 14. Allowed 0 to 300.

Default 6.5. Allowed 0 to 30.

HYPOTHETICAL

Option price
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Theta per day
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Prices are in index points (₹ per unit). Theta is the points the option loses in one calendar day if nothing else changes.

Days leftPriceChange vs now

Assumes Black-Scholes European pricing, no dividends and constant IV, with the numbers you typed.

Results are hypothetical and for illustration only. Not a guarantee. Not investment advice.

Model card
Name
Black-Scholes theta decay
Version
v1.0
Purpose
Show what time costs an option, under stated assumptions, for learning only.
Method
Black-Scholes European option, no dividends, constant implied volatility. Theta is the analytic value per calendar day.
Limitations
Ignores changes in IV, skew, transaction costs and taxes. Real option prices differ from the model, and early exercise is not modelled.
Last reviewed
4 Oct 2026
Important information
  • Education only. Daksh Analytics is not registered with SEBI and gives no buy or sell advice.
  • Data may be delayed. Items marked illustrative or hypothetical use made-up numbers.
  • Past results do not predict future results.
  • Derivatives carry a high risk of loss.

See Terms, Privacy and Data sources.

Education only. Daksh Analytics is not registered with SEBI and this is not investment advice. The result is a model estimate with the numbers you type in; real option prices differ.

What is theta decay? The clock on every option.

An option's price has two parts: intrinsic value, what it is worth if exercised now, and time value, what traders pay for the chance that it moves in their favour before expiry. Theta is how fast time value drains away.

Decay is not a straight line. For an at-the-money option it is slow when expiry is far and speeds up in the last week, so the final few days lose the most per day. Spot, strike, days left and IV are the inputs; the model assumes constant IV and no dividends.

See it move on the theta decay slider, or work out a likely daily range with the expected move calculator.