The option premium can be broken down into two components - intrinsic value and time value. The intrinsic value of a call is the amount the option is ITM, if it is ITM. If the call is OTM, its intrinsic value is zero. Putting it another way, the intrinsic value of a call is Max[0, (St — K)] which means the intrinsic value of a call is the greater of 0 or (St — K). Similarly, the intrinsic value of a put is Max[0, K — St],i.e. the greater of 0 or (K — St). K is the strike price and St is the spot price.
