A UK doctor has revealed the perfect time to go to sleep if you're looking to avoid those groggy, snooze-the-alarm, need caffeine-kind-of mornings.
Dr Karan Raj says most of us are getting our sleep cycles all wrong and it's making us feel more tired than we should - even when we get a full eight hours rest.
"Every night your brain moves through several sleep cycles," Dr Raj explains in a video to his 3.4 million TikTok followers.
"Each cycle starts with light sleep, then to deep sleep then dream sleep and back to light."
If we master the timing of these cycles and wake up towards the end of one we'll have a greater chance of waking up refreshed, says Dr Raj.
"Each of these cycles is around 90 minutes.
"You feel most refreshed if you wake up at the end of one of these 90-minute cycles because you're closest to your normal waking state."
Luckily for us, Dr Raj also has a simple equation to help you figure out the best bedtime for waking up at the end of a cycle.
"To increase the chances of this, first figure out what time you want to wake up… say 8am, work backwards in 90-minute blocks until you get to a time closest to when you want to sleep."
Working with an 8am wake up, the perfect time to fall asleep would be at 11pm if you wanted a nine-hour slumber or at 12:30am which would give you seven-and-a-half hours.
Falling asleep at these times means your 8am alarm would wake you up at the end of a 90-minute sleep cycle - which Dr Raj says will give you a much better chance at leaping out of bed bright-eyed and bushy-tailed.
His video has amassed more than 1.6 million views with TikTok users saying it helped to explain their sleeping troubles.
"That probably explains why I wake up every couple of hours... interesting" one user wrote.
"That's crazy, was wondering why I can have six or seven-and-a-half hours and feel great. Yet if I have eight hours I feel terrible."
Another sleep tip Dr Raj offers is to keep your window open at night. He says a closed-up room with minimal ventilation can lead to a rise in CO2 levels.
