Formal:
* Hindi ko alam. (This is the most common and literal translation.)
Informal:
* Ewan. (This is a more casual and everyday way to say it.)
* Di ko alam. (A shortened version of "Hindi ko alam.")
* Wala akong alam. (Literally means "I have no knowledge," but conveys the same meaning.)
Adding Emphasis:
* Talaga pong hindi ko alam. (This adds emphasis to the "I don't know," making it sound more sincere.)
* Ay, ewan ko. (This expresses surprise or confusion, like "Goodness, I don't know!")
Using the Tagalog word for "know":
* Hindi ko ma-gets. (This means "I don't understand," but can also be used to convey "I don't know.")
Choose the best option based on the situation.