When combined, the literal meaning is “not spending the effort of blowing away dust.” This powerful and descriptive image makes the meaning unforgettable.
Chinese idioms, or chengyu, often rely on vivid, concrete imagery to convey abstract concepts. 不费吹灰之力 is a prime example of this. While an English speaker might say “it was a piece of cake” or “a walk in the park,” these idioms associate ease with simple, pleasant activities. The Chinese idiom, however, defines ease by quantifying the *absolute minimum physical effort imaginable*—the tiny puff of air needed to move a speck of dust. This approach reflects a certain pragmatism and a focus on the physics of the action itself. It’s less about the task being pleasant and more about it being objectively, almost laughably, simple to execute. Using this idiom demonstrates a higher level of linguistic proficiency and an appreciation for the descriptive power embedded in the Chinese language. It shows you're not just translating words, but thinking in pictures, which is a cornerstone of mastering Chinese.
This idiom is widely used in both written and spoken Chinese. While it is a chengyu and thus has a slightly more literary feel than simple slang, it is perfectly normal to hear it in everyday conversations.