I got some mail from my boss. It contains:

I will tell the details tomorrow. I want to sleep on it.

What does this sentence mean?

  • 2
    She said why don't we both just sleep on it tonight / And I believe in the morning you'll begin to see the light Nov 25, 2013 at 22:02

3 Answers 3


They'd like to talk about it tomorrow, after they've had a night to think about it (presumably including a good night's sleep).

  • Is this a formal usage?
    – anish
    Nov 25, 2013 at 12:36
  • @anish I wouldn't say it's formal usage, but it's a common usage. Nov 25, 2013 at 13:43
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    @anish It isn't improper to use in a business setting, but it wouldn't go into any formal/legal document. It is perfectly acceptable to say to pretty much anyone that you want some time to "sleep on it." You just wouldn't write in a formal resignation, for example. "I've decided to leave the company after having slept on it" would look a little odd.
    – Gray
    Nov 25, 2013 at 13:44
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    "I'll decide whether to buy this mattress after I've had a chance to sleep on it." :-)
    – Jay
    Nov 25, 2013 at 15:57

While I don't disagree with snailboat's answer, I don't know if it quite captures the entire essence of it.

One source defines the idiom as:

sleep on it: take at least a day to think about something before making a decision.

So, yes, we are talking about a chance to make a decision overnight. However, it's worth mentioning that the general gist of the phrase means that give yourself time to consider what you are pondering, and you give yourself time to clear your head as well.

People often see a conundrum in a new light after they've had a chance to mull it over, talk about their feelings with others, and even get a good night's rest. Have you ever had an experience where something seemed very stressful at the time, but it looked very minor by the time you woke up in the morning? Or when a decision was hard to make in heat of the moment, but the right decision seemed obvious before you were even out of your pajamas the next day? The problem hadn't changed, but your perspective had. Taking the time to "sleep on" something gives you a chance to think about it for awhile – and to not think about it for awhile, too. Many sages advise people to avoid making major decisions until they have had a chance to "sleep on it:"

Make it your rule that you won't make a firm and final decision about any added costs until you've had a chance to sleep on it. In the morning, look at everything with fresh eyes and a well-rested perspective. (William J Hirsch, Jr, 2009)

Moreover, it's more than just a catch-phrase; it's apparently been backed up by hard science:

The idea that we need to "sleep on it" when faced with a big decision is no joke. We intuitively know that sleep helps us think better, stronger, and prepares our minds for optimal functionality. A Dutch study in 2006 points to the benefits of taking in information and letting the "unconscious" mind during sleep churn through the options involved. Other experiments have also backed this finding. (Michael Breus, 2007)

  • That means it is always used in decision making?
    – anish
    Nov 26, 2013 at 4:20
  • "Always" is a very strong word, and I like to avoid it when talking about usage. But yes, a majority of the time, when you "sleep on" something, that precedes making a decision. From Macmillan: sleep on something to wait to make a decision until the next day, after you have rested and had more time to think
    – J.R.
    Nov 26, 2013 at 9:38
  • Please give some other cases where we can use Sleep on it
    – anish
    Nov 26, 2013 at 12:33
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    I can't think of one right now, that's the point. But just because I can't think of one off the top of my head, doesn't mean there isn't one. I guess I'll have to just sleep on it.
    – J.R.
    Nov 26, 2013 at 13:25
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    @anish Married couples might agree to "Let's sleep on it" after a particularly intense session of quarrelling. There's a point where it's so late in the evening and neither wants to give in to the other, that the only solution available is to sleep on it.
    – Mari-Lou A
    Nov 26, 2013 at 19:35

Just adding my 2 cents point out that the phrase doesn't necessarily mean "tomorrow". The phrase is not to be taken so literally in terms of time; it just means, "I will take some time to think and I will allow space for new perceptions and feelings to arise". Sometimes you may "sleep on something" for a few days.

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