Tick value is the amount of money in the base currency of the instrument, that you gain or lose on the movement of one tick and is calculated as follows:
Tick value = contract size X tick size (the tick size and contract size is determined by the exchange and varies depending on the contract).
For example, the E-mini S&P 500 Future contract contains a national value of 50 times the S&P therefore the tick value calculation is 50*0.25= $12.50. Thus, when the price of a future contract goes up by one tick, the trader who has a long position, makes a profit of $ 12.5 per future.