Defending type
Normal Fire Water Grass Electric Ice Fighting Poison Ground Flying Psychic Bug Rock Ghost Dragon Dark Steel
A
t
t
a
c
k
i
n
g

t
y
p
e
Normal ½×½×
Fire ½×½×½×½×
Water ½×½×½×
Grass ½×½×½×½×½×½×½×
Electric ½×½×½×
Ice ½×½×½×½×
Fighting ½×½×½×½×
Poison ½×½×½×½×
Ground ½×½×
Flying ½×½×½×
Psychic ½×½×
Bug ½×½×½×½×½×½×
Rock ½×½×½×
Ghost ½×½×
Dragon ½×
Dark ½×½×½×
Steel ½×½×½×½×

Note:
This chart applies to games from Generations II, III, IV, and V, including relevant spinoffs.

Dual-type calculation:
To calculate the type effectiveness of a move on a dual-typed Pokémon, take the effectiveness of the attacking move on both types and multiply them together. For example, to calculate the damage an Electric-type move does to Dragonite (Dragon/Flying), we take Electric's effectiveness on the Dragon type (½×) and on the Flying type (2×) and multiply them together:
½ × 2 = 1 → Electric-type moves have a neutral (1×) effect on Dragonite.