Free Sleep Tools:
How Much Do You Actually Owe?
34 free calculators for understanding and optimizing your sleep — start with your Sleep Debt Calculator below, then explore cycles, caffeine, naps, and jet lag.
Last 7 nights of sleep
Estimated sleep shortfall
8.5h
Moderate
How we calculate this+
Shortfall is the sum of (target minus actual sleep) for every night you slept less than your target. Surplus is the sum of (actual sleep minus target) for every night you slept more. Net balance is surplus minus shortfall. We track these separately rather than letting one good night silently cancel out a bad one.
The estimated recovery window is a rough, transparent estimate, not a clinical prediction. There is no validated formula for exactly how long it takes an individual to recover from a given sleep shortfall; the range shown assumes roughly 30 to 60 extra minutes of sleep per night, a pace commonly discussed in sleep research. Actual recovery depends on the size and duration of the deficit, individual physiology, sleep quality, and consistency, and chronic long-term debt does not necessarily resolve on the same timeline as short-term debt.
Consistency compares how much your nightly sleep varies (statistically, the coefficient of variation) to a few rough bands — it's a simple variability measure, not a validated sleep-quality score.
This calculator is an educational estimate, not a medical device, and it cannot diagnose a sleep disorder. See our disclaimer for details.
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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 34 sleep tools
Each instant. Each free. No accounts.
Core tools
Sleep Debt Calculator: Track and Repay Lost Sleep
Sleep debt calculator: find out how many hours of sleep you owe your body and get a step-by-step plan to repay it.
Open toolSleep Cycle Calculator: Find Your Best Bedtime
Sleep cycle calculator: find the optimal bedtime or wake time aligned with your 90-minute sleep cycles.
Open toolWake-Up Time Calculator: Best Time to Wake Up
Wake-up time calculator: discover the best time to wake up based on when you go to sleep tonight.
Open toolBedtime Calculator: Find Your Ideal Sleep Time
Bedtime calculator: know exactly when to fall asleep based on your wake-up time and natural sleep cycles.
Open toolSleep Quality Score Calculator: Rate Your Sleep
Sleep quality score calculator: get a personalized score for how restorative your sleep really is.
Open toolSleep Efficiency Calculator: Know Your Percentage
Sleep efficiency calculator: find your sleep efficiency percentage, the gold-standard sleep quality metric.
Open toolREM Sleep Calculator: How Much REM You're Getting
REM sleep calculator: find out how much REM sleep you get per night and whether it's enough for memory and mood.
Open toolDeep Sleep Calculator: How Much You Really Need
Deep sleep calculator: find out how much slow-wave sleep you need, and estimate how much you're currently getting.
Open toolCircadian Rhythm Calculator: Find Your Rhythm
Circadian rhythm calculator: discover your ideal sleep-wake window and peak performance times by chronotype.
Open toolOptimal Sleep Window Calculator: Best Bed & Wake Time
Optimal sleep window calculator: find the exact bedtime and wake time that align with your circadian rhythm.
Open toolSleep Hours by Age Calculator: AASM Guidelines
Sleep hours by age calculator: find exactly how many hours of sleep you need, using the latest AASM and NSF guidelines.
Open toolSleep Pattern Calculator: Spot Your Irregularities
Sleep pattern calculator: analyze your weekly sleep pattern, spot social jet lag, and get a personalized fix.
Open toolExpansion tools
Nap Optimizer Calculator: Find Your Ideal Nap
Nap optimizer calculator: find the perfect nap length for your goal, whether it's alertness, recovery, or creativity.
Open toolCaffeine Cutoff Calculator: Time Your Last Cup
Caffeine cutoff calculator: find your ideal cutoff time so your afternoon coffee stops disrupting your sleep.
Open toolScreen Time Sleep Impact Calculator: See the Cost
Screen time sleep impact calculator: see how evening screen use delays your sleep and lowers sleep quality.
Open toolSleep Recovery Planner: Repay Your Sleep Debt
Sleep recovery planner: get a multi-day, science-based plan to recover from accumulated sleep debt.
Open toolWeekly Sleep Planner: Build a 7-Day Schedule
Weekly sleep planner: build a 7-day sleep schedule that actually matches your life and goals.
Open toolInsomnia Self-Assessment Tool: Free Screener
Insomnia self-assessment: take a clinically-inspired screener and find out if you may have chronic insomnia.
Open toolMelatonin Dosage Calculator: Find Your Right Dose
Melatonin dosage calculator: find the lowest effective dose and best timing for sleep onset or jet lag.
Open toolSleep Hygiene Checklist: 20-Point Free Audit
Sleep hygiene checklist: run a 20-point, evidence-based audit of your habits and get a personalized score.
Open toolInsomnia Severity Index Test: Clinical Screener
Insomnia Severity Index test: take the clinically validated 7-question ISI and get a science-backed treatment pathway.
Open toolSleep Onset Latency Calculator: How Fast You Fall Asleep
Sleep onset latency calculator: find out how long it takes you to fall asleep, and what that reveals about sleep pressure.
Open toolBiphasic Sleep Calculator: Plan a Split Schedule
Biphasic sleep calculator: plan a science-backed split schedule with a shorter night and a strategic day nap.
Open toolBaby Sleep Calculator: Sleep Needs by Age
Baby sleep calculator: find how much sleep your baby needs by age and build their ideal nap and night schedule.
Open toolBaby Nap Calculator: Perfect Nap Times by Age
Baby nap calculator: find the perfect nap times for your baby based on age and wake windows, protecting night sleep.
Open toolWork Schedule Sleep Calculator: Shift Sleep Debt
Work schedule sleep calculator: estimate how your shift pattern affects sleep opportunity and weekly sleep debt.
Open toolViral tools
Why Am I Tired Analyzer: Find the Real Reason
Why am I tired: answer that question with a quick diagnostic that finds the most likely reasons you're exhausted.
Open toolSleep Productivity Loss Calculator: See the Cost
Sleep productivity loss calculator: quantify how much focus and output you're losing to poor sleep.
Open toolLife Hours Lost Calculator: Cumulative Sleep Cost
Life hours lost calculator: project cumulative under-rested waking hours from chronic under-sleeping over time.
Open toolJet Lag Recovery Calculator: Adjust Time Zones Fast
Jet lag recovery calculator: estimate how long it'll take to adjust to a new time zone, and how to speed it up.
Open toolSleep Apnea Risk Screener: Free STOP-BANG Test
Sleep apnea risk screener: take a STOP-BANG-style screening for obstructive sleep apnea risk in under a minute.
Open toolChronotype Quiz: Find Your Sleep Animal Type
Chronotype quiz: are you a Lion, Bear, Wolf, or Dolphin? Find your chronotype and your ideal daily schedule.
Open toolSleep Myth-Buster Quiz: Test What You Know
Sleep myth-buster quiz: test what you really know about sleep and bust 12 of the most common myths.
Open toolSleep Age Calculator: Your Biological Sleep Age
Sleep age calculator: discover how old your sleep habits make you biologically, based on duration 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.
Sleep advice for your city and your job
Light pollution, time zones, and work schedules all change how much sleep debt you accumulate — and how you recover from it. Explore sleep data specific to where you live and what you do.
Sleep by city
Real, sourced sleep data — average sleep duration, light pollution, and local survey findings — for major cities worldwide.
- → Sleep in New York City
- → Sleep in London
- → Sleep in Tokyo
- → Sleep in Singapore
- → Sleep in Dubai
- → Sleep in Los Angeles
Sleep by profession
How shift work, rotating schedules, and irregular hours affect sleep debt in specific jobs — plus practical recovery strategies for each.
See all professionsThe 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.
Sleep science, explained
The key terms behind every calculator on this site — each one links to the tool that measures it.
- Sleep debt
- The cumulative gap between the sleep you need and the sleep you actually get, measured in hours.
- Sleep cycle
- A roughly 90-minute loop through light sleep, deep sleep, and REM sleep. Adults complete 4–6 cycles per night.
- REM sleep
- The sleep stage responsible for dreaming, emotional processing, and memory consolidation. Dominant in later sleep cycles.
- Deep sleep
- Slow-wave (N3) sleep — the stage responsible for physical recovery, immune regulation, and glymphatic waste clearance.
- Circadian rhythm
- Your internal 24-hour clock, anchored by light, food, and temperature cues, that governs when you feel sleepy or alert.
- Chronotype
- Your genetically influenced tendency toward morning or evening alertness — commonly called being a 'lark' or an 'owl'.
- Sleep efficiency
- The percentage of time in bed actually spent asleep. 85% or higher is considered healthy; below 85% suggests fragmented sleep.
- Sleep latency
- How long it takes to fall asleep after getting into bed. Under 20 minutes is typical; much shorter can itself signal sleep debt.
- Insomnia
- Persistent difficulty falling or staying asleep despite adequate opportunity to sleep, often assessed with a standardized severity scale.
- Sleep apnea risk
- Repeated breathing interruptions during sleep that fragment rest and reduce oxygen levels — screenable with a short symptom questionnaire.
- Melatonin
- The hormone that signals your body it's time to sleep. Timing and dose both affect its usefulness for shifting sleep schedules.
- Jet lag
- Circadian misalignment from crossing time zones faster than your internal clock can adjust, causing fatigue and disrupted sleep.
- Social jet lag
- The mismatch between your body clock and your social schedule — like sleeping much later on weekends than weekdays.
- Sleep hygiene
- The habits and environment (light, temperature, screens, caffeine timing) that support consistent, high-quality sleep.
- Power nap
- A short, strategically timed nap (typically 10–20 minutes) that reduces sleepiness without causing grogginess or disrupting nighttime sleep.
- Caffeine half-life
- The roughly 5–6 hours it takes your body to clear half a dose of caffeine — the basis for calculating a personal caffeine cutoff time.
From the Sleep Library
Long-form, science-backed deep dives.
optimization · 13 min
How to Use Sleep Restriction Therapy at Home: Step-by-Step
Sleep restriction therapy can be used safely at home when done correctly. Here's the evidence-based method, step by step.
health · 13 min
What Foods to Eat at Night to Increase Melatonin Naturally
What foods to eat at night to increase melatonin naturally — ranked by evidence. Learn what foods to eat at night to increase melatonin naturally and sleep faster
optimization · 8 min
Productivity Loss Calculator: Sleep Debt Costs 6-54 Workdays
Productivity loss calculator: sleep debt costs the average person 6-54 lost workdays a year — find your specific dollar cost in seconds.
health · 13 min
Tired But Can't Sleep: Causes, Science, and Solutions
Feeling tired but unable to sleep usually has biological causes, not psychological ones. Understand what's really happening — and what actually fixes it.
health · 16 min
Why Digital Nomads Suffer From Constant Circadian Disruption
Why digital nomads suffer from constant circadian disruption: frequent time zone shifts and irregular schedules take a real, measurable toll on the body
optimization · 16 min
Sleep Hygiene Checklist: 15 Science-Backed Habits
Not all sleep hygiene advice carries equal weight. This evidence-ranked checklist covers the 15 habits with the strongest research behind them.
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.
What is sleep efficiency, and what's a good score?+
Sleep efficiency is the percentage of time in bed that you actually spend asleep. Healthy adults typically score 85–95%; below 85% often signals fragmented sleep, insomnia, or poor sleep hygiene.
What's the difference between REM sleep and deep sleep?+
Deep sleep (slow-wave, N3) dominates early sleep cycles and drives physical recovery and immune function. REM sleep dominates later cycles and drives emotional processing, memory consolidation, and dreaming. You need both, and cutting sleep short disproportionately cuts REM.
Does napping help with sleep debt?+
A well-timed 10–20 minute nap can reduce sleepiness and modestly offset acute sleep debt, but it doesn't substitute for adequate nightly sleep and can disrupt nighttime sleep if taken too late or too long.
What is social jet lag?+
Social jet lag is the mismatch between your body's internal clock and your social schedule — for example, sleeping much later on weekends than weekdays. It's associated with the same metabolic and mood effects as real jet lag, even though you never left home.
What time should I go to bed?+
Work backward from when you need to wake up: subtract your personal sleep need (typically 7–9 hours) plus the ~15 minutes it usually takes to fall asleep, and round to the end of a 90-minute sleep cycle for an easier wake-up. Our bedtime calculator does this math for you.
How long is a sleep cycle?+
A full sleep cycle — light sleep, deep sleep, then REM — runs roughly 90 minutes, though it can range from about 70 to 120 minutes and shifts across the night as REM periods lengthen. Most adults complete 4–6 cycles per night.
What is my chronotype?+
Your chronotype is your natural tendency toward morning or evening alertness — commonly grouped into 'lark' (early riser), 'owl' (night person), and intermediate types. It's influenced by genetics and shifts somewhat with age. Take our 2-minute chronotype quiz to find yours.
How do I know if I have insomnia?+
Occasional trouble sleeping is normal, but insomnia is typically defined as difficulty falling or staying asleep at least 3 nights a week for a month or more, with real daytime impact on mood, energy, or focus. Our Insomnia Severity Index screening tool uses a standardized questionnaire to help you gauge severity — it's not a diagnosis, but it's a useful starting point before talking to a doctor.
How much sleep debt is too much?+
There's no universal cutoff, but a running deficit of more than about 10 hours starts producing measurable declines in attention, mood, and reaction time for most people, and debt beyond 15–20 hours is generally considered severe. What matters most is the trend: a small, chronic nightly shortfall compounds faster than most people expect.