The game uses softened type factors
A weakness is 1.6×, a resistance is 0.6×, and a main-series immunity becomes 0.3×. Neutral is 1×. Two defending types multiply together: 1.6 × 1.6 = 2.56× for a double weakness, while 1.6 × 0.6 = 0.96× for a mixed matchup.
Use the active move’s type, not the attacking partner’s species types. Read the chart by row (attack) and column (defense). It lists one defending type at a time.
Two examples you can use during a run
A Fire move against a Grass / Steel target gets 1.6 × 1.6 = 2.56× from typing. At full rain intensity, Fire’s 0.5× weather factor changes that part of the calculation to 1.28×. This is before attack stats, defenses and other modifiers.
An Electric move against Water / Ground gets 1.6 × 0.3 = 0.48×. Ground’s main-series immunity is softened here; it does not make the attack deal zero damage.
Physical and special defenses are a separate step
Physical attacks use the target’s Defense; special attacks use Special Defense. A base defense of 75 gives a 1× defense factor; 150 gives about 0.78× incoming damage. The factor is softened and capped between 0.78× and 1.25×. Armor cards and held items are separate modifiers. Arceus’s pure damage and map hazards do not follow this defense rule.