-(느)ㄴ다고 치다 — assuming that, suppose that, let’s say

1. This expression is used when acknowledging or assuming someone's assertion or behavior or acknowledging or assuming that some situation exists.

The following clause usually contains a rebuttal of the preceding clause or a description of a problem that arises if one acknowledges the preceding clause.

It is mainly used in the forms -(느)ㄴ다고 치자(칩시다), -(느)ㄴ다고 쳐도 and -(느)ㄴ다고 치고.

It can also be used in the form -(느)ㄴ다 치다 in which -고 is deleted.

2. This expression is used when assuming some action or situation or when hypothesizing it to be true.

In this case, it is often used in the form -(느)ㄴ다고 치고.

It can also be used in the form -(느)ㄴ다 치다，in which -고 is deleted.

Details

1. When this expression is used in the sense described in 1. above, it is often used in conversation in the forms of 그렇다고 치자, 그렇다고 쳐도 and 그렇다고 치고 when both parties are already aware of or understand the situation or context being described.

어제는 비가 와서 그렇다고 치고 오늘은 왜 또 늦은 건데?

10년 동안 연락 한 번 없었던 건 그렇다고 쳐도 왜 날 보고도 모르는 척한 거야?

2. When used in the sense described in 2. above, this expression can be substituted with -는 셈치다 with no major change in meaning.

남들은 살 빼려고 일부러 돈 내고 헬스클럽에도 가는데 너도 운동하는 셈치고 그 정도 거리는 걸어 다니면 어떻겠니?

이 밤에 여기도 겨우 찾았는데 그냥 휴가철에 온 셈치고 마음 편하게 지내다가 갑시다.

3. This expression is also used when describing a situation that hasn't occurred yet or when describing an imagined or hypothetical situation different from the current reality.

가: 관성 이 뭐예요? 예를 들어서 가르쳐 주세요.

What's inertia? Please teach me with an example.

나: 네가 버스를 탔다고 치자. 달리던 버스가 갑자기 멈추면 앞으로 넘어지지? 그걸 관성이라고 하는 거야.

Let's pretend you're on a bus. If the moving bus suddenly stops, you fall forward, right? That's what is called inertia.

가: 제품에 대해서 열심히 공부하긴 했는데 손님들이 오시면 잘 설명할 수 있을지 모르겠어요.

I've studied the product well, but I don't know if I can adequately explain it to customers.

나: 그럼 내가 손님이라고 치고 제품에 대해서 설명해 보세요.

In that case, pretend I'm a customer and explain the product to me.

Kimchi Reader

To assume or consider a hypothetical scenario as if it were true.