Find the best time to set your alarm

Wake-up calculator: the best time to set your alarm

If you are heading to bed right now, the wake-up calculator tells you what time to wake up so that your alarm lands at the end of a sleep cycle. Enter the time you plan to go to sleep, or choose "sleep now", and the tool adds the minutes it takes you to drift off, then counts forward in 90-minute cycles. The times it lists are the moments when your sleep is expected to be lightest, which is when getting out of bed is easiest.

People search for this as a "wake up calculator", a "what time should I wake up" tool or a "sleep cycle alarm". All of them describe the same need: choose an alarm time that gives you enough sleep and does not pull you out of deep sleep. Because it runs in your browser, there is nothing to install and nothing to sign in to.

How to use the wake-up calculator

Pick the time you expect to fall asleep. If you are going to lie down now, the "sleep now" option uses the current time. The calculator adds your time to fall asleep, 15 minutes by default, then shows the wake-up times that complete four, five or six full cycles. A five-cycle result means about seven and a half hours of sleep, and six cycles means nine hours. You can open the fine-tune panel to change the fall-asleep time and cycle length if you know yours is different.

Choose the latest time that still lets you start your day without rushing. Setting an alarm for the first available cycle may sound responsible, but a short night, even a perfectly timed one, adds to sleep debt if you repeat it.

Why the alarm time matters as much as the bedtime

Sleep inertia is the groggy, slow feeling after waking. It is strongest when you are woken from deep sleep and can last 30 minutes or longer. Waking near the end of a cycle, when sleep is lighter, tends to reduce it. That is the reasoning behind smart alarms in sleep apps and wearables, which try to detect light sleep and ring within a window before your deadline. A simple calculator achieves a similar result by choosing the right end point in advance, with no microphone or sensor.

Light, movement and a glass of water also help you shake off inertia. Opening the curtains or stepping outside within the first half hour tells your body clock that the day has begun.

Wake-up calculator versus a smart alarm on a sleep tracker

A smart alarm is a feature of an app or watch. It watches your movement or heart rate, estimates when you are in light sleep, and wakes you in a short window before your latest time. The idea is sound, but accuracy depends on the device, and the window is usually 10 to 30 minutes long. A calculator does not measure anything. It uses the average cycle length to plan the night, which means it works for everyone but is less personal.

Many people combine the two. Plan the night with the calculator, then set a smart alarm window around the result. For a full comparison of devices and apps that offer smart alarms, see our guides to the best sleep tracker and the Apple Watch sleep tracker.

Sleeping in a hotel, on a plane or after a late night

The calculator is most useful when your night is unusual. After a late event you may have only four and a half hours available. The tool will show a four-cycle option for six hours and a three-cycle option to avoid a mid-cycle wake-up, but it will not pretend that short sleep is healthy. When you travel across time zones, combine it with the jet lag planner. When you are about to start a night shift, the shift work sleep planner handles the longer blocks.

Ready-made wake-up times

If you already know your target, jump to a prepared page: going to bed at 10:00 PM, going to bed at 11:00 PM or going to bed at midnight. Each one lists the wake-up times for that bedtime. For the reverse question, the bedtime calculator starts from the alarm and works backwards.

Habits that make the wake-up time stick

Keep your wake-up time within about an hour every day of the week, including weekends. Place the alarm across the room, avoid hitting snooze repeatedly because the fragments of sleep you gain are low in quality, and get daylight early. If you still cannot get up, the cause may be too little total sleep, a late body clock or something else entirely. Our chronotype quiz helps you see whether you are naturally an early or a late person, and the sleep diary shows how your real wake-up times compare with your plan.

Setting an alarm that does not rely on willpower

Good alarm habits matter as much as the time you choose. Put the alarm out of reach so that you must stand up, choose a sound that is firm but not alarming, and avoid stacking ten snoozes. Each snooze lets you slip back into a new, fragmented sleep cycle that you cannot finish, which can make you feel worse. A single alarm at a sensible time beats a series of early ones.

Weekend wake-ups and social jet lag

Sleeping three hours later on Saturday and Sunday shifts your body clock in the same way as travelling west. Monday morning then feels like an early flight east. If you must sleep in, limit it to about an hour, get out into daylight soon after you get up and keep your Sunday night bedtime close to normal. Our chronotype quiz helps you see whether your preferences are naturally late.

Wake-up times for common bedtimes

Here are some quick references, assuming 15 minutes to fall asleep. Going to bed at 10:00 PM: alarm at 4:15 AM, 5:45 AM or 7:15 AM for four, five and six cycles. Bed at 11:00 PM: 5:15 AM, 6:45 AM or 8:15 AM. Bed at midnight: 6:15 AM, 7:45 AM or 9:15 AM. Each of these has a full page, such as bed at 10:30 PM, so you can look up the exact list. The calculator above adjusts for your own time to fall asleep.

Frequently asked questions