Enter your desired wake-up time and an estimate of how long it takes you to fall asleep. This calculator will suggest optimal bedtimes based on 90-minute sleep cycles, helping you wake up feeling refreshed.
Your recommended bedtimes will appear here.
function formatMinutesToTime(totalMinutes) {
// Handle negative minutes (previous day)
while (totalMinutes = 12 ? 'PM' : 'AM';
hours = hours % 12;
hours = hours ? hours : 12; // The hour '0' should be '12'
minutes = minutes < 10 ? '0' + minutes : minutes;
return hours + ':' + minutes + ' ' + ampm;
}
function calculateBedtimes() {
var wakeUpTimeInput = document.getElementById("wakeUpTime").value;
var fallAsleepTimeInput = document.getElementById("fallAsleepTime").value;
var resultsDiv = document.getElementById("bedtimeResults");
resultsDiv.innerHTML = ""; // Clear previous results
if (!wakeUpTimeInput) {
resultsDiv.innerHTML = "Please enter your desired wake-up time.";
return;
}
var fallAsleepMinutes = parseFloat(fallAsleepTimeInput);
if (isNaN(fallAsleepMinutes) || fallAsleepMinutes < 0) {
fallAsleepMinutes = 15; // Default to 15 minutes if invalid
document.getElementById("fallAsleepTime").value = 15; // Update input field
resultsDiv.innerHTML += "Invalid 'Time to fall asleep'. Defaulting to 15 minutes.";
}
// Parse wake-up time (HH:MM format from input type="time")
var timeParts = wakeUpTimeInput.split(':');
var wakeUpHour = parseInt(timeParts[0], 10);
var wakeUpMinute = parseInt(timeParts[1], 10);
var wakeUpTotalMinutes = (wakeUpHour * 60) + wakeUpMinute;
var sleepCycleDuration = 90; // minutes
var bedtimes = [];
// Calculate for 7, 6, 5, 4 sleep cycles (most common recommendations)
// Display from longest sleep duration to shortest
var cyclesToCalculate = [7, 6, 5, 4];
for (var i = 0; i < cyclesToCalculate.length; i++) {
var numCycles = cyclesToCalculate[i];
var totalSleepDuration = numCycles * sleepCycleDuration;
var timeToStartSleeping = wakeUpTotalMinutes – totalSleepDuration;
var bedtimeTotalMinutes = timeToStartSleeping – fallAsleepMinutes;
bedtimes.push({
time: formatMinutesToTime(bedtimeTotalMinutes),
cycles: numCycles,
duration: totalSleepDuration
});
}
var resultHtml = "
Recommended Bedtimes:
";
resultHtml += "To wake up at " + formatMinutesToTime(wakeUpTotalMinutes) + " feeling refreshed, consider going to bed at one of these times:";
for (var j = 0; j < bedtimes.length; j++) {
var bedtime = bedtimes[j];
var hours = Math.floor(bedtime.duration / 60);
var minutes = bedtime.duration % 60;
resultHtml += "Go to bed at " + bedtime.time + " for " + bedtime.cycles + " sleep cycles (" + hours + "h " + minutes + "m of actual sleep).";
}
resultHtml += "These times allow you to wake up at the end of a sleep cycle, which can help you feel more rested and less groggy.";
resultsDiv.innerHTML = resultHtml;
}
Understanding Your Sleep Cycles
The Sleepyti.me Bedtime Calculator is based on the principle of sleep cycles. A typical human sleep cycle lasts approximately 90 minutes. During this time, your body progresses through different stages of sleep, from light sleep to deep sleep (REM sleep) and back again.
Waking up in the middle of a deep sleep cycle can leave you feeling groggy, disoriented, and tired, even if you've had a sufficient amount of sleep. Conversely, waking up at the end of a sleep cycle, when your body is in a lighter stage of sleep, can make you feel more refreshed and energized.
How It Works
This calculator takes your desired wake-up time and works backward, subtracting full 90-minute sleep cycles, plus the estimated time it takes you to fall asleep. It provides several bedtime options, typically aiming for 4, 5, 6, or 7 full sleep cycles, which correspond to 6, 7.5, 9, or 10.5 hours of actual sleep, respectively.
4 Cycles (6 hours): Suitable for shorter nights or if you need to wake up earlier than usual.
5 Cycles (7.5 hours): A common and often recommended duration for adults.
6 Cycles (9 hours): Ideal for those who need more sleep, such as teenagers or individuals with higher sleep requirements.
7 Cycles (10.5 hours): For those who need extended rest or are catching up on sleep.
Tips for Better Sleep Hygiene
Beyond calculating your optimal bedtime, practicing good sleep hygiene is crucial for consistent, quality sleep:
Maintain a Consistent Sleep Schedule: Go to bed and wake up at the same time every day, even on weekends. This helps regulate your body's natural sleep-wake cycle (circadian rhythm).
Create a Relaxing Bedtime Routine: Wind down with activities like reading, a warm bath, or meditation. Avoid stimulating activities before bed.
Optimize Your Sleep Environment: Ensure your bedroom is dark, quiet, cool (ideally between 60-67°F or 15-19°C), and comfortable. Invest in a good mattress and pillows.
Limit Screen Time Before Bed: The blue light emitted from smartphones, tablets, and computers can suppress melatonin production, making it harder to fall asleep. Try to avoid screens for at least an hour before bed.
Watch Your Diet: Avoid heavy meals, caffeine, and alcohol close to bedtime. Caffeine can stay in your system for hours, and alcohol, while initially sedating, can disrupt sleep later in the night.
Regular Exercise: Physical activity can significantly improve sleep quality, but avoid intense workouts too close to bedtime, as they can be stimulating.
Manage Stress: Stress and anxiety are common causes of sleep problems. Practice relaxation techniques, mindfulness, or journaling to help calm your mind before sleep.
By combining the insights from this calculator with healthy sleep habits, you can significantly improve your sleep quality and overall well-being, leading to more productive days and a healthier life.