How much sleep
do you actually owe?
The complete toolkit for understanding and optimizing your sleep — from debt and cycles to caffeine, naps, and jet lag.
Last 7 nights of sleep
33
Free calculators
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Science-backed
Why sleep optimization matters more than you think
Sleep debt is the most underdiagnosed driver of fatigue, low productivity, weight gain, and brain fog. The good news: it's highly measurable and highly fixable.
Sleep debt damages cognition
Two weeks of 6-hour nights produce cognitive impairment equivalent to 48 straight hours of zero sleep. Sleep deprivation silently erodes memory, decision quality, and creative insight — even when you feel 'fine'.
Poor sleep wrecks metabolism
Just 4 nights of restricted sleep reduce insulin sensitivity by up to 30%. Sleep deprivation drives ghrelin up, leptin down, and pushes you toward weight gain, blood sugar instability, and chronic fatigue.
Sleep optimization compounds
Small, consistent improvements to your sleep schedule, caffeine cutoff, and morning light exposure deliver compounding returns to your energy, focus, mood, and long-term health.
All 33 sleep tools
Each instant. Each free. No accounts.
Core tools
Sleep Debt Calculator
Calculate how many hours of sleep you owe your body and how to repay it.
Open toolSleep Cycle Calculator
Find the optimal bedtime or wake time aligned with your 90-minute sleep cycles.
Open toolWake-Up Time Calculator
Discover the best time to wake up based on when you go to sleep.
Open toolBedtime Calculator
Know exactly when to fall asleep based on your wake-up time and sleep cycles.
Open toolSleep Quality Score Calculator
Get a personalized score for the quality of your sleep based on key indicators.
Open toolSleep Efficiency Calculator
Calculate your sleep efficiency percentage — the gold-standard sleep quality metric.
Open toolREM Sleep Calculator
Calculate how much REM sleep you get per night and whether it's enough for memory, learning, and emotional health.
Open toolDeep Sleep Calculator
Find out how much deep sleep (slow-wave sleep) you need and how much you're likely getting based on your age and sleep duration.
Open toolCircadian Rhythm Calculator
Discover your personal circadian rhythm, ideal sleep-wake window, and peak performance times based on your chronotype and light exposure.
Open toolOptimal Sleep Window Calculator
Calculate your personalised optimal sleep window — the exact bedtime and wake time that aligns with your circadian rhythm for deepest, most restorative sleep.
Open toolSleep Hours by Age Calculator
Find out exactly how many hours of sleep you need based on your age, using the latest AASM and NSF guidelines.
Open toolSleep Pattern Calculator
Analyse your weekly sleep pattern, identify irregularities and social jet lag, and get a personalised schedule to fix it.
Open toolExpansion tools
Nap Optimizer Calculator
Find the perfect nap length for your goal — alertness, recovery, or creativity.
Open toolCaffeine Cutoff Calculator
Stop drinking coffee at the right time to protect your sleep.
Open toolScreen Time Sleep Impact Calculator
See how evening screen time delays your sleep and reduces sleep quality.
Open toolSleep Recovery Planner
Get a multi-day plan to recover from accumulated sleep debt.
Open toolWeekly Sleep Planner
Build a 7-day sleep schedule that matches your life and goals.
Open toolInsomnia Self-Assessment Tool
Take a clinically-inspired insomnia screener and find out if you may have chronic insomnia.
Open toolMelatonin Dosage Calculator
Find the lowest effective melatonin dose and timing for your goal — sleep onset or jet lag.
Open toolSleep Hygiene Checklist
A 20-point evidence-based sleep hygiene audit with a personalized score.
Open toolInsomnia Severity Index Test
Take the clinically validated 7-question ISI psychological test for insomnia. Get a severity score and a science-backed treatment pathway.
Open toolSleep Onset Latency Calculator
How long does it take you to fall asleep? Find out if your sleep onset latency is healthy and what it reveals about your sleep drive.
Open toolBiphasic Sleep Calculator
Plan a science-backed biphasic sleep schedule — a shorter night sleep plus a strategic daytime nap — for better alertness and productivity.
Open toolBaby Sleep Calculator
Calculate how much sleep your baby needs by age, find their ideal nap and nighttime schedule, and understand normal sleep development.
Open toolBaby Nap Calculator
Find the perfect nap times for your baby based on age and wake windows. Build a consistent nap schedule that protects night sleep.
Open toolViral tools
Why Am I Tired Analyzer
Diagnose the most likely reasons you're feeling exhausted.
Open toolSleep Productivity Loss Calculator
Quantify how much focus and output you lose to poor sleep.
Open toolLife Hours Lost Calculator
See how many waking years you lose to chronic under-sleeping.
Open toolJet Lag Recovery Calculator
Estimate how long it'll take to adjust to a new time zone — and accelerate it.
Open toolSleep Apnea Risk Screener
STOP-BANG-style screening for obstructive sleep apnea risk in under a minute.
Open toolChronotype Quiz
Are you a Lion, Bear, Wolf, or Dolphin? Find your chronotype and ideal schedule.
Open toolSleep Myth-Buster Quiz
Test what you really know about sleep — bust 12 of the most common myths.
Open toolSleep Age Calculator
Discover your 'sleep age' — how old your sleep health makes you biologically — based on your duration, quality, timing, and consistency.
Open toolHow to use SleepDebtCalc
A 4-step path from chronically tired to consistently rested.
01
Measure your sleep debt
Log your last 7 nights and your individual sleep need. Get an instant deficit calculation in hours.
02
Find your perfect bedtime
Use the bedtime, wake-up, and sleep cycle calculators to align your schedule with the 90-minute architecture of sleep.
03
Build a recovery plan
Generate a 5–7 day plan that repays sleep debt without disrupting your circadian rhythm or weekend life.
04
Optimize the inputs
Lock in your caffeine cutoff, screen-time limits, and nap window with the rest of the toolkit.
Topic clusters
Sleep optimization
Cycles, bedtime, wake time, recovery — engineered together.
Productivity
Quantify and reverse focus loss from poor sleep.
Health optimization
Caffeine, screens, naps and the science of feeling rested.
The science behind the calculators
Sleep cycles & sleep architecture
Human sleep runs in 90-minute cycles through light N1, light N2, deep slow-wave N3, and REM sleep. Early cycles are rich in deep sleep — the stage responsible for physical recovery, glymphatic waste clearance, and immune regulation. Late cycles are rich in REM sleep, which drives emotional processing and creative consolidation.
Sleep debt & sleep deprivation
Sleep debt is the cumulative gap between your sleep need and your actual sleep duration. Every hour below your need accumulates and compounds, producing measurable declines in attention, mood, metabolism, and immune function — even when you don't subjectively feel tired.
Circadian rhythm
Your circadian clock is anchored by light, food, and temperature signals. Morning sunlight triggers cortisol; evening darkness triggers melatonin. Irregular schedules cause "social jet lag" — biologically equivalent to flying across two time zones every weekend.
Sleep efficiency & sleep quality
Sleep efficiency is time asleep divided by time in bed. Healthy adults score 85–95%. Below 80% suggests fragmented sleep, insomnia, or poor sleep hygiene. Combined with sleep duration and morning energy, efficiency is the single best predictor of daytime performance.
From the Sleep Library
Long-form, science-backed deep dives.
optimization · 18 min
What Is Sleep Debt? The Complete Science-Based Guide (2026)
Sleep debt explained: how it builds, what it really costs your brain, body, mood and finances — and the exact 5-day science-based recovery protocol that actually works.
optimization · 16 min
Sleep Cycles Explained: How 90-Minute Stages Shape Your Rest
Sleep cycles explained: the 90-minute REM/NREM architecture, why mid-cycle wake-ups ruin mornings, and how to align your bedtime with biology.
productivity · 15 min
The Real Cost of Poor Sleep on Productivity (And How to Fix It)
Poor sleep costs more than energy — it drains your output, your paycheck, and your years. Here's the recovery protocol elite performers, founders, and athletes use to reverse it.
Sleep debt, explained
What is sleep debt?+
Sleep debt is the cumulative difference between the sleep you need (typically 7–9 hours) and the sleep you actually get. It builds up night by night and impairs cognition, mood, immunity, and metabolism.
Can you fully recover from sleep debt?+
Short-term debt (a few nights) can be largely repaid with consistent extra sleep over 1–2 weeks. Chronic, long-term debt has lingering effects even after recovery sleep, so prevention beats repayment.
How is sleep debt calculated?+
We compare your nightly sleep against your individual sleep need across the past 7–14 days. The total deficit, in hours, is your sleep debt.
Is sleeping in on weekends enough?+
It helps reduce acute debt but doesn't fully reverse it, and it can disrupt your circadian rhythm. A consistent schedule plus 30–60 extra minutes nightly is more effective.