Is "I have no idea" same as "I don't know?"

Native speaker’s answer
Rebecca
Yes, that's spot on! To "have no idea" means to "not know at all." However, the phrase "I have no idea" expresses more emphasis than "I don't know." Ex: I have no idea what to eat tonight. => more emphasis = I don't know what to eat tonight. Ex: She has no idea what she's doing.