.sleep-cycle-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #fdfdfd;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
color: #333;
}
.sleep-cycle-calculator-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
font-size: 1.8em;
border-bottom: 2px solid #4CAF50;
padding-bottom: 10px;
}
.sleep-cycle-calculator-container h3 {
color: #34495e;
margin-top: 30px;
margin-bottom: 15px;
font-size: 1.4em;
}
.sleep-cycle-calculator-container .input-group {
margin-bottom: 15px;
display: flex;
flex-wrap: wrap;
align-items: center;
gap: 10px;
}
.sleep-cycle-calculator-container .input-group label {
flex: 1 1 100px;
font-weight: bold;
color: #555;
font-size: 0.95em;
}
.sleep-cycle-calculator-container .input-group input[type="number"],
.sleep-cycle-calculator-container .input-group select {
flex: 2 1 80px;
padding: 10px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
box-sizing: border-box;
max-width: 120px; /* Limit width for time inputs */
}
.sleep-cycle-calculator-container .input-group select {
max-width: 80px;
}
.sleep-cycle-calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #4CAF50;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 20px;
}
.sleep-cycle-calculator-container button:hover {
background-color: #45a049;
}
.sleep-cycle-calculator-container .result-section {
margin-top: 25px;
padding: 15px;
background-color: #e8f5e9;
border: 1px solid #c8e6c9;
border-radius: 8px;
min-height: 50px;
}
.sleep-cycle-calculator-container .result-section p {
margin: 5px 0;
font-size: 1.1em;
line-height: 1.6;
color: #388e3c;
}
.sleep-cycle-calculator-container .result-section strong {
color: #1b5e20;
}
.sleep-cycle-calculator-container .error-message {
color: #d32f2f;
font-weight: bold;
margin-top: 10px;
}
.sleep-cycle-calculator-container .info-box {
background-color: #e3f2fd;
border: 1px solid #90caf9;
border-radius: 8px;
padding: 15px;
margin-top: 25px;
font-size: 0.95em;
line-height: 1.6;
color: #2196f3;
}
.sleep-cycle-calculator-container .info-box strong {
color: #1976d2;
}
.sleep-cycle-calculator-container .article-content {
margin-top: 30px;
line-height: 1.7;
color: #444;
}
.sleep-cycle-calculator-container .article-content h3 {
color: #2c3e50;
font-size: 1.5em;
margin-top: 25px;
margin-bottom: 15px;
}
.sleep-cycle-calculator-container .article-content p {
margin-bottom: 1em;
}
.sleep-cycle-calculator-container .article-content ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 1em;
}
.sleep-cycle-calculator-container .article-content li {
margin-bottom: 0.5em;
}
@media (max-width: 600px) {
.sleep-cycle-calculator-container {
padding: 15px;
}
.sleep-cycle-calculator-container .input-group {
flex-direction: column;
align-items: flex-start;
}
.sleep-cycle-calculator-container .input-group label {
width: 100%;
margin-bottom: 5px;
}
.sleep-cycle-calculator-container .input-group input[type="number"],
.sleep-cycle-calculator-container .input-group select {
max-width: 100%;
width: 100%;
}
}
function formatTime(date) {
var hours = date.getHours();
var minutes = date.getMinutes();
var ampm = hours >= 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 parseTimeInput(hourId, minuteId, ampmId) {
var hourStr = document.getElementById(hourId).value;
var minuteStr = document.getElementById(minuteId).value;
var ampm = document.getElementById(ampmId).value;
var hour = parseInt(hourStr, 10);
var minute = parseInt(minuteStr, 10);
if (isNaN(hour) || isNaN(minute) || hour 12 || minute 59) {
return null;
}
if (ampm === 'PM' && hour !== 12) {
hour += 12;
} else if (ampm === 'AM' && hour === 12) {
hour = 0; // Midnight
}
return { hour: hour, minute: minute };
}
function calculateWakeUpTimes() {
var inputTime = parseTimeInput('bedtimeHour', 'bedtimeMinute', 'bedtimeAMPM');
var resultDiv = document.getElementById('wakeUpResult');
resultDiv.innerHTML = "; // Clear previous results
if (inputTime === null) {
resultDiv.innerHTML = 'Please enter a valid bedtime (e.g., 10:30 PM).';
return;
}
var now = new Date();
var bedtime = new Date(now.getFullYear(), now.getMonth(), now.getDate(), inputTime.hour, inputTime.minute, 0);
// Add 15 minutes for falling asleep
bedtime.setMinutes(bedtime.getMinutes() + 15);
var cycles = [3, 4, 5, 6, 7]; // Number of 90-minute cycles
var sleepDurations = [4.5, 6, 7.5, 9, 10.5]; // Corresponding hours of actual sleep
resultDiv.innerHTML += 'If you go to bed at ' + formatTime(new Date(now.getFullYear(), now.getMonth(), now.getDate(), inputTime.hour, inputTime.minute, 0)) + ', you should aim to wake up at one of these times:';
for (var i = 0; i < cycles.length; i++) {
var wakeUpTime = new Date(bedtime.getTime());
wakeUpTime.setMinutes(wakeUpTime.getMinutes() + (cycles[i] * 90));
resultDiv.innerHTML += 'For ' + sleepDurations[i] + ' hours of actual sleep (' + cycles[i] + ' cycles): ' + formatTime(wakeUpTime) + '';
}
}
function calculateBedtimes() {
var inputTime = parseTimeInput('wakeupHour', 'wakeupMinute', 'wakeupAMPM');
var resultDiv = document.getElementById('bedtimeResult');
resultDiv.innerHTML = "; // Clear previous results
if (inputTime === null) {
resultDiv.innerHTML = 'Please enter a valid wake-up time (e.g., 7:00 AM).';
return;
}
var now = new Date();
var wakeupTime = new Date(now.getFullYear(), now.getMonth(), now.getDate(), inputTime.hour, inputTime.minute, 0);
var cycles = [3, 4, 5, 6, 7]; // Number of 90-minute cycles
var sleepDurations = [4.5, 6, 7.5, 9, 10.5]; // Corresponding hours of actual sleep
resultDiv.innerHTML += 'If you need to wake up at ' + formatTime(wakeupTime) + ', you should aim to go to bed at one of these times:';
for (var i = 0; i < cycles.length; i++) {
var bedtime = new Date(wakeupTime.getTime());
bedtime.setMinutes(bedtime.getMinutes() – (cycles[i] * 90));
// Subtract 15 minutes for falling asleep buffer
bedtime.setMinutes(bedtime.getMinutes() – 15);
// If bedtime is on the previous day, adjust for display
var displayBedtime = new Date(bedtime.getTime());
if (displayBedtime.getDate() < wakeupTime.getDate()) {
resultDiv.innerHTML += 'For ' + sleepDurations[i] + ' hours of actual sleep (' + cycles[i] + ' cycles): ' + formatTime(displayBedtime) + ' (the previous night)';
} else {
resultDiv.innerHTML += 'For ' + sleepDurations[i] + ' hours of actual sleep (' + cycles[i] + ' cycles): ' + formatTime(displayBedtime) + '';
}
}
}
// Initial calculation on page load for default values
document.addEventListener('DOMContentLoaded', function() {
calculateWakeUpTimes();
calculateBedtimes();
});
Sleep Cycle Calculator
How it works: This calculator helps you find optimal bedtimes or wake-up times based on 90-minute sleep cycles. It adds a 15-minute buffer for the average time it takes to fall asleep. Waking up at the end of a sleep cycle can help you feel more refreshed.
Calculate Optimal Wake-Up Times
AM
PM
Calculate Optimal Bedtimes
AM
PM
Understanding Your Sleep Cycles
Sleep is not a continuous, uniform state. Instead, it's a complex process that cycles through different stages, each lasting approximately 90 minutes. These are known as sleep cycles. Understanding and aligning your wake-up time with the end of a sleep cycle can significantly impact how refreshed and energized you feel throughout the day.
The Stages of Sleep
A typical sleep cycle consists of four distinct stages:
- NREM Stage 1 (N1): This is the lightest stage of sleep, often described as drowsiness. You can be easily awakened during this phase.
- NREM Stage 2 (N2): Your heart rate and breathing slow down, and your body temperature drops. This stage accounts for about 50% of your total sleep.
- NREM Stage 3 (N3): This is deep, slow-wave sleep, crucial for physical restoration, growth, and immune function. It's the hardest stage to wake someone from.
- REM Sleep: Rapid Eye Movement sleep is characterized by vivid dreaming, increased brain activity, and temporary muscle paralysis. It's vital for cognitive functions like memory consolidation and emotional processing.
These stages repeat throughout the night, with the proportion of REM sleep increasing in later cycles.
Why Wake Up Between Cycles?
Waking up during a deep sleep stage (N3) can leave you feeling groggy, disoriented, and tired, a phenomenon known as sleep inertia. Conversely, waking up at the end of a sleep cycle, typically during a lighter stage (N1, N2, or even just after REM), allows your body to transition more naturally to wakefulness. This can lead to:
- Increased alertness and energy upon waking.
- Reduced feelings of grogginess and fatigue.
- Improved mood and cognitive performance.
How to Use the Sleep Cycle Calculator
Our Sleep Cycle Calculator helps you pinpoint these optimal times. It works by adding or subtracting multiples of 90 minutes (the average length of a sleep cycle) from your desired bedtime or wake-up time. We also factor in an average of 15 minutes for the time it takes most people to fall asleep, ensuring the calculations are as accurate as possible for your actual sleep duration.
- To find optimal wake-up times: Enter the time you plan to go to bed. The calculator will suggest several wake-up times, each corresponding to the end of a sleep cycle, allowing for 4.5, 6, 7.5, or 9 hours of actual sleep.
- To find optimal bedtimes: Enter the time you need to wake up. The calculator will suggest bedtimes that allow you to wake up at the end of a sleep cycle, after 4.5, 6, 7.5, or 9 hours of actual sleep.
Important Considerations
While the 90-minute cycle is a good average, individual sleep cycle lengths can vary slightly (from 70 to 110 minutes). Factors like age, genetics, lifestyle, and health conditions can influence this. Use this calculator as a guide, and pay attention to how you feel. Experiment with different wake-up or bedtimes to find what works best for your body.
Consistency is also key. Going to bed and waking up at roughly the same time each day, even on weekends, helps regulate your body's natural circadian rhythm, leading to better overall sleep quality.