How can calculate the impurity limits of any drug from its daily dosage?

Impurities limits can be fixed based on the following categories,

1. Daily dose of the drug product

2. Based on the toxicity of the impurity (specific cases)

for complete information visit the ICH Q3 guidelines for all type of impurities in drug substances and drug products.

would you share the product name so that we can give better info/ conclusion.