how accurate is IV numbers?

Discussion in 'Options' started by newguy05, Feb 20, 2011.

  1. Does anyone know how accurate is ivolatility's IV numbers. I need a way to check a stock's IV now vs 1 week vs 1 month ago see how expensive it currently is..on my phone. fits the bill pretty well but have doubts about their accuracy. For example nvda it has:

    current / 1week ago / 1month ago
    IV Index call 49.11% 60.92% 55.09%
    IV Index put 48.97% 60.74% 55.50%
    IV Index mean 49.04% 60.83% 55.30%

    nflx has:

    current / 1week ago / 1month ago
    IV Index call 42.79% 40.60% 56.16%
    IV Index put 42.50% 40.97% 55.85%
    IV Index mean 42.65% 40.79% 56.01%
  2. newguy,

    I don't understand why you say you don't trust - what is wrong the numbers you are showing for the examples? I think ivolatility is probably quite accurate and certainly good enough for most use.

    Otherwise, the other options I could think of would be OptionsXpress has a chart that shows IV in recent months, but I don't think you can even get it out as a number - just in chart format.

    A better choice if checking weekly is enough might be Larry McMillian's free Options Volatility Data updated weekly here:

    Again though I'm not sure why you seem to think Ivolatilities numbers might be wrong - I use their charts quite often to view where a current IV is compared to general in the last 6 months or 1 year.

  3. They look slightly high to me.

    My numbers are:

    -25d/50d/25d/Expiry Month/Date
    40.07 42.26 44.46 MAR 20110218
    38.49 40.31 42.12 MAR 20110211
    25.60 34.78 43.95 FEB 20110211
    53.48 54.33 55.18 FEB 20110118
  4. spindr0


    You might consider checking with IVolatility to see how they calculate their IV numbers because I think they use a weighted algorithm.
  5. yeah i did, the actual iv #s doesnt matter too much for me, as long as the comparison between current/1week/1month is accurate and calculated the same way. They look to be fine after comparing with optionsxpress and fidelity, thanks guys.