Wellness Calculators
Free wellness calculators for sleep debt, sleep timing, hydration, and daily health habits. Science-based tools for better rest and daily routines.
Wellness Calculators - Build Better Daily Habits
Good health is built on daily habits: consistent sleep, adequate hydration, and mindful routines. The calculators below help you turn generic advice into precise, personalised targets grounded in research.
Three Wellness Calculators
Sleep Calculator - Find the ideal bedtime or wake-up time based on 90-minute sleep cycles. Enter your wake time to see recommended bedtimes for 4 to 7 complete cycles, or enter your bedtime to find the best wake times. Includes a configurable fall-asleep offset (default 14 minutes). Shows total sleep duration and a quality rating for each cycle count.
Sleep Debt Calculator - Quantify your cumulative sleep deficit in hours. Quick Check mode analyses a single night; Weekly Tracker mode lets you log all 7 nights and calculates the total weekly sleep debt. Shows severity rating (Mild, Moderate, Severe), average nightly shortfall, and estimated number of recovery nights needed.
Epworth Sleepiness Scale Calculator - Rate your chance of dozing in 8 standardised everyday situations to compute your ESS score (0–24). Scores above 10 indicate excessive daytime sleepiness. Shows severity category (normal, mild, moderate, severe) with clinical guidance. Widely used for obstructive sleep apnea and narcolepsy screening.
Frequently Asked Questions
How many hours of sleep do adults need?
The National Sleep Foundation recommends 7 to 9 hours per night for adults aged 18 to 64, and 7 to 8 hours for adults 65 and older. Teenagers (14 to 17) need 8 to 10 hours; school-age children need 9 to 11 hours. Individual variation exists, but consistently sleeping fewer than 7 hours is associated with increased risk of cardiovascular disease, obesity, and impaired cognitive function.
What is a sleep cycle and how long does it last?
A sleep cycle is one complete progression through all sleep stages: NREM Stage 1 (light sleep), NREM Stage 2 (light sleep), NREM Stage 3 (deep slow-wave sleep), and REM (rapid eye movement sleep). One full cycle takes approximately 90 minutes. Adults complete 4 to 6 cycles per night, with deeper sleep concentrated in earlier cycles and REM increasing toward morning.
Why does waking at the end of a sleep cycle feel better?
Waking mid-cycle, especially during deep NREM Stage 3 sleep, causes sleep inertia: grogginess, disorientation, and reduced cognitive performance that can last 15 to 60 minutes. Timing your alarm to coincide with the end of a 90-minute cycle means you wake during lighter NREM Stage 1 or 2, where the body is already transitioning toward wakefulness. The Sleep Calculator automates this timing for you.