The ratio of calcium ions to gellan gum needed for gelation can vary depending on several factors, such as the specific type of gellan gum being used, the pH of the solution, the concentration of gellan gum, and the presence of other ingredients in the mixture.

In general, a typical range for the ratio of calcium ions to gellan gum is between 0.02 to 0.04% calcium ions (as calcium chloride or another calcium salt) to 0.1 to 0.5% gellan gum by weight, depending on the specific application and desired texture. However, the optimal ratio for successful gelation may vary depending on the specific recipe and process being used.

It's important to note that the calcium ions are typically added to the solution after the gellan gum has been dispersed and hydrated, and the solution is heated to promote gel formation. Additionally, it's recommended to use food-grade calcium salts and to dissolve them thoroughly in the liquid before adding the gellan gum to ensure even distribution of the calcium ions.

Overall, when using gellan gum for gelation, it's important to carefully follow a reliable recipe and instructions to determine the optimal ratio of calcium ions to gellan gum needed for successful gel formation.