When do we use this expression "let's just say" and what does it exactly mean?
"Let's say" or "let's just say" has two common meanings:
(a) What follows is an example, a premise, or a hypothetical situation that the speaker will assume to be true for purposes of discussion.
For example: "This investment will grow by 10% per year. Let's say you started with $1000. After a year you would have $1100. After two years you would have $1210. Etc."
Or, "Let's say that we have a permanent base on the Moon by 2030. That base could then be used to ..."
(b) What follows is the speaker's understanding of a consensus or agreement that has been reached, or a condition that he wants the other party to agree to. Often used after a discussion about a disagreement.
Example: "Okay, so let's just say that you'll put up $10,000 and I'll put up $5,000."
"Let's just say" is a transition to an examination of a particular option, regardless of whether the option is real, acceptable, agreed upon, etc.
Here's an example where the context should be simple enough to demonstrate its usage:
John: "I will arrive at the movie theater at 7:00 PM when the movie starts."
Jill: "John, you will never arrive by 7:00 if you are coming from the other side of the city through traffic."
John: "I will certainly be there at 7:00."
Jill: "Ok, let's just say you do arrive by 7:00. You will still be late because you have to wait in line to purchase the movie ticket."
In this example you can see that Jill thinks that John will be late to the movie. John says he will be on time, but Jill tries to say that arriving at 7:00 isn't even enough because of the line.
An equivalent phrase to "let's just say" would be "even if you were". Jill could have said,
"Even if you were there at 7:00, you would still be late because you have to wait in line to purchase the movie ticket."
In addition, "let's just say" can be used when a scenario has unknown aspects:
Jill: "John, can you really finish 4 sodas during the movie?"
John: "I'm not sure. I know that the movie is 2 hours long, but I don't know how long it takes to drink 1 soda."
Jill: "That is true. Let's just say you drink 1 soda every 45 minutes. You wouldn't finish all 4 during the movie."
John: "Yes, but let's just say I can drink 1 soda every 30 minutes. Then, I would be able to finish all 4 during the movie."
"Let's just say" could also be used to question an assumption. A business might plan to purchase a building, make renovations to the building, open the building for customers, and continue to run the store. The business may spend a lot of time planning the renovations, planning how to sell their goods, and planning how to run the store. However, someone might say, "Let's just say we can't buy the building to begin with. Then, what will we do?"
It is a statement made to indicate a situation a person doesn't want to just come out and say they enjoyed.
let's just say I wasn't mad about it.
And it is used to say that you are not going to give someone all the details about something.
Let’s just say she wasn’t very pleased about it.