play around with some numbers..here: http://www.cboe.com/framed/IVolframed.aspx?content=http%3a%2f%2fcboe.ivolatility.com%2fcalc%2findex.j%3fcontract%3d9E73B166-4AD9-49DA-8C8C-8F5BF3D6843D§ionName=SEC_TRADING_TOOLS&title=CBOE%20-%20IVolatility%20Services closer to 20 imo