# Calculating theta

Hello everyone.

I hope you are all doing fine. I’m new to this forum and English is not my native language. So I apologize for my bad grammar in advance.

I have question about theta of the Option greek.

I tried to calculate but it’s have always have the answer between 4 and 5. While the answer should be - 0.01305
In the input are:

Underlying stock is 48.60
Strike price is 50
Intrest rate is 1%
Volatility 20%
Expiration date is 60

Base on black scholes data
N(d2) is 0.3555
D1 is - 0,28

Could some please tell me what I did wrong. Thank you very much

I get θc = −4.76.

Perhaps you did nothing wrong.

I got -0.0131.

The first and second term in the theta formula is a minus rather than plus sign. If you dont do that, you will have a positive answer.

For the whole thing, you have to divide by 365.

So the ambiguity is whether it’s a daily theta vs. an annual theta.

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First of all thank you for taking time to reply.

secondly i have calculate the option greek

I have almost the same answer. but according to the calculator the theta should be -0.01305
I have the same delta, gamma and vega but theta is difference and i dont know why

thank you for the reply. but i still have around 4 value

I suspect that it’s simply a rounding issue; if you round −0.01305 to 4 decimal places, you get −0.0131.

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I rounded to 4 decimal places in my spreadsheet.

Yup.

thats not what i mean

If you at my spreadsheet. you ll see that the delta, gamma and vega are the same as the calculator. but when you look at the theta. you will see that i have 4.58 and the calculator have -0.01305. my question is what did i do wrong

Its true. thank you so much

I finally understand what you said and its works thank you

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