The science
The methodology behind your sleep age.
Every factor weight in the calculator is grounded in peer-reviewed research. Here's what we measure, why we measure it, and the papers we lean on.
How the formula works
Sleep age = chronological age + sum of factor adjustments. Each factor adds or subtracts years based on how your input compares with research-backed optimal ranges. Adjustments are clamped to keep the output meaningful for healthy populations and direction their wellness toward what actually moves outcomes — not toward extremes designed to alarm.
The ten factors.
Weights are absolute year-magnitudes, applied with sign based on the input's distance from the optimal range. The weight column shows the maximum impact in either direction.
| Factor | Weight | What it captures | Sources |
|---|---|---|---|
Sleep duration Total nightly sleep compared with the 7–9h adult range. Both ends of the curve add years; chronic short sleep dominates. | ±5 yr | Total nightly sleep compared with the 7–9h adult range. Both ends of the curve add years; chronic short sleep dominates. | Hirshkowitz 2015 · Cappuccio 2010 |
Sleep quality Self-rated restorativeness on a 1–10 scale. Maps to PSQI subjective sleep quality. | ±4 yr | Self-rated restorativeness on a 1–10 scale. Maps to PSQI subjective sleep quality. | Buysse 1989 |
Sleep latency Time from lights-out to sleep onset. Latency >30 min is associated with insomnia phenotype. | ±2 yr | Time from lights-out to sleep onset. Latency >30 min is associated with insomnia phenotype. | Morin 2011 |
Night wakings Frequency of awakenings that fragment sleep architecture and reduce slow-wave time. | ±3 yr | Frequency of awakenings that fragment sleep architecture and reduce slow-wave time. | Stepanski 1987 |
Schedule consistency Variability of bedtime / wake time across the week. Higher variability is associated with metabolic risk. | ±3 yr | Variability of bedtime / wake time across the week. Higher variability is associated with metabolic risk. | Lunsford-Avery 2018 |
Caffeine intake Daily mg load and timing. Caffeine within 6 hours of bedtime measurably reduces sleep efficiency. | ±2 yr | Daily mg load and timing. Caffeine within 6 hours of bedtime measurably reduces sleep efficiency. | Drake 2013 |
Screens before bed Blue-light + cognitive arousal in the 60-minute window before sleep onset. | ±1 yr | Blue-light + cognitive arousal in the 60-minute window before sleep onset. | Chang 2015 |
Exercise frequency Moderate-to-vigorous activity days per week. Strong dose-response on subjective sleep quality. | ±2 yr | Moderate-to-vigorous activity days per week. Strong dose-response on subjective sleep quality. | Kredlow 2015 |
Stress level Self-rated psychological load. Affects sleep onset and architecture more than duration. | ±2 yr | Self-rated psychological load. Affects sleep onset and architecture more than duration. | Kim 2007 |
Studies cited.
A non-exhaustive list of the peer-reviewed work that shapes our scoring. We review and update this list every six months.
National Sleep Foundation's sleep time duration recommendations: methodology and results summary.
Hirshkowitz M., et al. · Sleep Health · 2015
View studySleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies.
Cappuccio F.P., et al. · Sleep · 2010
View studyThe Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research.
Buysse D.J., et al. · Psychiatry Research · 1989
View studyValidation of the Insomnia Severity Index as an outcome measure for insomnia research.
Morin C.M., et al. · Sleep Medicine · 2011
View studySleep variability across the lifespan: associations with mood and metabolic risk.
Lunsford-Avery J.R., et al. · Sleep · 2018
View studyCaffeine effects on sleep taken 0, 3, or 6 hours before going to bed.
Drake C., et al. · Journal of Clinical Sleep Medicine · 2013
View studyEvening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.
Chang A.M., et al. · PNAS · 2015
View studyThe effects of physical activity on sleep: a meta-analytic review.
Kredlow M.A., et al. · Journal of Behavioral Medicine · 2015
View study
Related references
For journalists, researchers & bloggers.
- Sleep Statistics 2026 — 75+ verified, cite-ready facts sourced from CDC, NHLBI, BLS, RAND, AASM, and peer-reviewed research.
- Embed the calculator — free iframe widget for publishers, with copy-paste snippets and a public methodology link.
- Press & media kit — logos, founder bio, boilerplate, and direct contact for fact-checking.