Do you ever go to bed ridiculously early because you need to wake up on time for work - then feel even more tired in the morning?
Well, you might be doing it wrong.
Don't just think by getting more hours of sleep, you'll be more refreshed in the office the next day. Apparently it's a bit more complicated than that.
But, luckily for us, someone has created a 'sleep calculator', being used on home decor site Hillarys, so we can work out when we need to hit the sack in the click of a button.
Apparently it's all to do with sleep cycles rather than getting more hours of sleep. If you wake up at the wrong time during a sleep cycle, you'll find yourself more tired - even if you were asleep for longer.
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If you need to get up at 7am
Need to make sure you're awake and getting out of bed at 7am? Then you need to go to bed at either 9.46pm or 11.16pm.
If you're having a late night and you don't fancy either of these, then 12.46am and 2.16am will also work.
The sleep calculator factors in the average of 14 minutes it takes people to naturally fall asleep, so you don't necessarily need to be in bed by this time.
If you need to get up at 6am
To get up at 6am, you're looking at a bedtime of 8.46pm, 10.16pm or even 11.46pm or - if you're feeling like a real night owl - 1.16am.
How about 8am?
Don't need to get up super early to get to work on time? Have no fear. Here's what time you need to go to bed for an 8am rise: 10.46pm, 12.16am, 1.46am or 3.16am.
What are sleep cycles?
A sleep cycle lasts about 90 minutes, during which time we move through five stages of sleep - four stages of non-rapid eye movement (NREM) sleep and one stage of rapid eye movement (REM) sleep.
We move from light sleep in Stage 1 to a very deep sleep in Stage 4. It is difficult to wake someone in Stage 4 of a sleep cycle, which is why you might feel more groggy if you wake up during this stage.
The fifth stage, REM sleep, is when most dreaming occurs.
You can even be really precise
For example, if you know getting out of bed at 6:35 is the optimum time so you can not miss the train and be punctual for work, enter it into the sleep calculator and you'll get a result.
For a 6.35am rise time, go to bed at 9.21pm, 10.51pm, 12.21am or 1.51am.
The Sleep Calculator website reads: "Getting a good night's sleep is about more than simply going to bed early – it's about waking up at the right time too.
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"Using a formula based on the body's natural rhythms, the Sleep Calculator will work out the best time for you to rise or go to sleep."
The calculator works on the principle that everyone sleeps in about five or six cycles which last roughly 90 minutes.
Waking up midway through a cycle can leave you unable to sleep and feeling grumpy the next day. The idea is to wake up in between cycles and feel refreshed in the morning.
