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.

Source