Sleep Calculator
Tell us your age and when you need to wake up, and we will work out how much sleep you actually need, your ideal bedtime, and the sleep cycle options that will help you wake up feeling human.
Most of us guess at our bedtime and hope for the best. This calculator takes out the guesswork. It uses sleep duration ranges from the National Sleep Foundation and the World Health Organization, then works backward from your wake-up time so you know exactly when to switch off the lights.
It also factors in 90-minute sleep cycles. Waking at the end of a cycle, when your sleep is naturally lightest, tends to feel far easier than being dragged out of deep sleep by an alarm. If you tell us you have been feeling run down, we will also give you a rough sleep debt estimate so you can see how much catching up your body might be asking for. Curious what short sleep does over time? Our guide to sleep deprivation effects in Asian adults digs into the research.
Find Your Ideal Bedtime
😴 Your Sleep Plan
⚚️ Medical disclaimer: For general guidance only. Consult a healthcare professional for personal medical advice. Sleep cycle length and sleep needs vary between people and from night to night.
How to Use This Calculator
Pick your age group
Sleep needs change a lot with age, so this sets the recommended range from WHO and National Sleep Foundation guidance.
Enter your wake time
Put in the time you usually need to be up. We count back in 90-minute cycles and add 15 minutes to fall asleep.
Rate how rested you feel
Slide from 1 to 10. Score below 6 and we will add a rough sleep debt estimate to your results.
What affects sleep quality?
Hitting the right number of hours is only half the story. These five things quietly make or break how good that sleep actually is. Tap to expand.
The five biggest sleep quality factors
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📱 Blue light and screens
Bright screen light in the evening suppresses melatonin, the hormone that tells your body it is time to sleep, which can push your body clock later. Try to dim screens and step away from your phone about an hour before bed, or use a warm night mode.
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☕ Caffeine
Caffeine has a half-life of roughly 5 to 6 hours, so an afternoon coffee can still be in your system at midnight. If you are sensitive or struggling to fall asleep, keep coffee, strong tea, and energy drinks to the morning.
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🍷 Alcohol
A nightcap can help you nod off, but alcohol fragments the second half of the night and cuts into restorative REM sleep. You end up sleeping lighter and waking more often, even if you do not remember it.
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🌡️ Room temperature
Your core body temperature needs to drop slightly for good sleep. A cool room, roughly 18 to 20 degrees Celsius for most people, helps that happen. In warm, humid Asian climates, a fan or air conditioning often makes a real difference.
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🏃 Exercise timing
Regular exercise deepens sleep, but intense workouts in the last hour or two before bed can leave you too wired and warm to drift off. Morning or early evening movement tends to help sleep most. Gentle stretching at night is fine.
Frequently Asked Questions
How much sleep do I actually need by age?
Sleep needs fall as you grow. The National Sleep Foundation recommends about 10 to 14 hours for young children under 6, 9 to 11 hours for ages 6 to 12, 8 to 10 hours for teens 13 to 17, 7 to 9 hours for adults from 18 to 60, and 7 to 8 hours for adults 61 and over. These are healthy ranges, and where you sit inside them is personal.
What time should I go to bed if I wake at 7am?
For a typical adult who needs about 8 hours and takes 15 minutes to fall asleep, a 7am wake time means lights out around 10:45pm. To land at the end of a 90-minute sleep cycle, good bedtimes are about 10pm for 6 cycles or 11:30pm for 5 cycles. Enter your own wake time above for exact bedtimes.
What is a sleep cycle and why does 90 minutes matter?
A sleep cycle lasts roughly 90 minutes and moves through light sleep, deep sleep, and REM sleep. Waking at the end of a cycle, when sleep is lightest, usually feels easier than being pulled out of deep sleep. That is why this calculator suggests bedtimes in whole 90-minute blocks, adding 15 minutes to fall asleep.
What is sleep debt and can you recover it?
Sleep debt is the running total of sleep you miss versus what your body needs. If you need 8 hours but average 6.5 on weeknights, you build roughly 1.5 hours of debt each night. You can recover some of it with a few nights of longer, consistent sleep, but chronic short sleep is linked with weight gain, low mood, and higher long-term health risk, so steady habits beat weekend catch-up.
Does the WHO say how much sleep children need?
Yes. The World Health Organization's 2019 guidelines for children under 5 recommend 14 to 17 hours for newborns, 12 to 16 hours for infants, 11 to 14 hours for ages 1 to 2, and 10 to 13 hours for ages 3 to 4, including naps. These match the National Sleep Foundation ranges and show just how much more sleep young children need than adults.
How much sleep you need, and why it changes
There is no single magic number for sleep. Your needs shift across your whole life, which is why this calculator asks your age first. Newborns can need up to 17 hours, school-age kids around 9 to 11, and most adults settle into a 7 to 9 hour window that holds fairly steady until later life, when it drifts a little shorter. These ranges come from a major review by the National Sleep Foundation, published in the journal Sleep Health in 2015, which brought together a panel of sleep experts to agree on healthy amounts by age.
For the youngest children, the World Health Organization set out clear sleep targets in its 2019 guidelines on physical activity, sedentary behaviour, and sleep for children under 5. The two sets of guidance line up closely, which is reassuring. What both make clear is that consistently short sleep is not something to shrug off. It is linked with weight gain, weaker focus, low mood, and higher long-term health risk.
The Singapore and Asia sleep squeeze
Across fast-paced Asian cities, sleep is often the first thing that gets sacrificed. Long working hours, packed commutes, a strong late-night supper culture, and constant screens all eat into the night. If that sounds familiar, you are not alone, and small consistent changes usually beat one heroic early night. For more, see our sleep and health guide.
Sources: National Sleep Foundation, sleep duration recommendations (Hirshkowitz et al., Sleep Health, 2015), sleepfoundation.org. World Health Organization, guidelines on physical activity, sedentary behaviour and sleep for children under 5 years of age (2019), who.int.