In Gen 7, the base chance is still **1/4096** and boosted to approximately **1/1365**.

However, the most effective method in Gen 7 is SOS battles. The chance of finding a shiny Pokemon without the shiny charm is **1/1024**. With the shiny charm, the chance is approximately **1/683** (rounded up). Putting each probability to common denominators, you have:

**4/4096** (without charm) vs. **6/4096** (with charm).

Therefore, with the shiny charm, it increases the probability by **50%** (1.5x). However, since we're talking about two still very low scales, you should really look at it as an increase from approximately 0.0977% to 0.146% chance (where both are still less than 1%).

Hope I helped! :)