Intrinsic value is the portion of the option premium that is in the money. If the stock price is above the strike price of the call option, the intrinsic value of the option can be calculated by taking the difference between the current stock price and the strike price of the option. Conversely, if the stock price is less than the strike price of the put option, the intrinsic value of the option can be calculated by taking the difference between the strike price and the current price of the stock.
Up until options expiration, a call option will have value even when the stock price is below the strike price. This value will represent the time premium component of the option. At expiration, time value will have fully decayed and the option will only be worth its' intrinsic value.