# Rate of Options decay

I know "Time decay accelerates on nearing expiry". But I want to know the rate of acceleration.

1. How curvy is the theta curve? Answers could be like,

Provided IV is stable, in a 3-month contract,

Month 1: time value losses 10%

Month 2: time value losses 30%

Month 3: time value losses 60%

1. Does theta work following a standard curve every time? Or it has other factors to affect?
2. It works same for all OTM, ATM and ITM? I read OTM options decelerate last month. Is that true?

The value of a call option that is near ATM can be approximated as $C(S,T)≈ 0.4 \sigma \sqrt T$. Therefore, under the unrealistic assumption that S does not change very much (i.e. the option stays near the money) the value decays as the square root of the remaining time.