If you use an Ultra Ball with no status conditions, the default catch rate is raised by 2×.
Here are the benefits from status conditions:
- Frozen: 2
- Sleep: 2
- Paralysis: 1.5
- Burn: 1.5
- Poison: 1.5
- None: 1
If you already caught your box-Legendary (Xerneas/Yveltal), I suggest you save your Master Ball for Zygarde.
Source
No status conditions (full HP): You have a 2.635% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 26 balls and at least a 95% chance of catching it within 113 balls.
No status conditions (1 HP): You have a 5.982% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 12 balls and at least a 95% chance of catching it within 49 balls.
Poisoned/Paralyzed/Burned (full HP): You have a 3.571% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 20 balls and at least a 95% chance of catching it within 83 balls.
Poisoned/Paralyzed/Burned (1 HP): You have a 8.107% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 9 balls and at least a 95% chance of catching it within 36 balls.
Asleep/Frozen (full HP): You have a 5.24% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 13 balls and at least a 95% chance of catching it within 56 balls.
Asleep/Frozen (1 HP): You have a 11.892% chance of capturing it per ball. Thus, you have at least a 50% chance of catching it within 6 balls and at least a 95% chance of catching it within 24 balls.
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