GO uses per-throw catch chance = 1 − (1 − BCR/(2 × CPM))^(ball × berry × throw × curve × medal). BCR is the Pokémon's base catch rate, CPM is its level-based multiplier, and every bonus is a separate multiplier on the exponent.

Nice = 1.0–1.3, Great = 1.3–1.7, Excellent = 1.7–2.0 (scales by circle size). Curveball adds a flat 1.7× multiplier and stacks with throw bonus and berries.

Golden Razz gives a 2.5× multiplier, which is the highest-single-throw bonus in the game. It still stacks with throw, curve, medal, and ball multipliers, so Excellent Curve + Golden Razz is the strongest normal-Ball combo.

Bronze = 1.1×, Silver = 1.2×, Gold = 1.3× per matching type. A Pokémon with two types counts the average of both medals if they differ.

Higher-level Pokémon have higher CPM values, and BCR is divided by (2 × CPM). Catching a raid boss (level 20 / 25) or a weather-boosted Pokémon is meaningfully harder than the same species at level 1.

The tool shows cumulative odds over N balls: 1 − (1 − p)^N, where p is your per-throw chance. This is useful for raids and legendary catches where you need to know 'will I land it in 5 Premier Balls?'.