Assuming constant volatility, what does the ATM theta against time graph look like?
( is a constant)
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
For ATM options:
V C = V P ≈ S σ 2 π t
Differentiating with respect to t :
θ A T M = ∂ t ∂ V ≈ t k
See Straddle Approximation Formula .