Child's play vs Piece of cake

When to use each in English, with meaning, register, and examples.

Child's play

InformalBeyond 10,000 (less common)

Piece of cake

InformalTop 3,000 (common)
Most common: Piece of cake
 Child's playPiece of cake
Pronunciation🇬🇧 //tʃaɪldz pleɪ//🇺🇸 //tʃaɪldz pleɪ//🇬🇧 //piːs əv keɪk//🇺🇸 //pis əv keɪk//
MeaningSomething easy to do.Something that is very easy to do.
ExampleThe game was child's play for him, as he had played it many times before.The test was a piece of cake; I finished it in just 20 minutes.
RegisterInformalInformal
How commonBeyond 10,000 (less common)Top 3,000 (common)
Collocationsconsidered child's play, it's child's play, make it child's playmake it a piece of cake, call it a piece of cake, find it a piece of cake
Common mistakesUsed in serious contexts where a more formal expression is needed., Confused with 'child's play' as a literal reference to children's activities.Using it to describe serious tasks., Confused with 'slice of cake', which has a different meaning., Misusing it in a negative context.
Usage notesUsed casually to describe tasks that require little effort or skill. Often used in contrast to more difficult tasks. It may not be appropriate in formal writing or discussions.Used in casual conversations to describe an easy task. Avoid in formal or academic contexts.

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Child's play

Frequently asked questions: Child's play vs Piece of cake

What's the difference between Child's play and Piece of cake?

Child's play: Something easy to do. Piece of cake: Something that is very easy to do.

Which is more common: Child's play and Piece of cake?

Piece of cake is the most common in everyday English.

Can you show an example of each?

Child's play: The game was child's play for him, as he had played it many times before. Piece of cake: The test was a piece of cake; I finished it in just 20 minutes.

Can I use Child's play and Piece of cake interchangeably?

Not always. Child's play and Piece of cake are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.