Same-type attack bonus, commonly abbreviated as STAB, is a 50% boost to the power of an attack when the attack is the same type as one of the types of the Pokémon using the attack. This results in a 50% increase in damage (100% if the Pokémon has the Adaptability Ability).
STAB doesn't add 25 Base Power to the original Base Power, but it boosts the Base Power by 50%, and 1.5 equals 50%.
So a 75 Base Power Thunder Punch*1.5=112.5 Base Power which equals 112 Base Power.
>in other words how much does stab give to all moves.
commented 11 minutes ago by OriginalGamer100
STAB applies to all moves that are the same type as the user. Basically multiply the Base Power of a move by 1.5 if you have STAB.