Enter your numbers
10 questions. Questions that only apply to some people appear once your earlier answers decide that they do.
From your health data
9 of these questions can be answered from lab results and device data you have already connected: Age, Night 1 — hours asleep, Night 2 — hours asleep, Night 3 — hours asleep, Night 4 — hours asleep, Night 5 — hours asleep, Night 6 — hours asleep, Night 7 — hours asleep, Sleep on days with no alarm and no obligations. Connect them once in your member account and they arrive here pre-filled and labelled as coming from your health data — and you can always type over the value.
Set up health data in your member account
This public page never reads your health data. Pre-filling happens inside the signed-in app, which is a separate, access-controlled surface.
How this is calculated
Formula version lll-sleep-debt-1.0.0
For each of seven nights the shortfall against an assumed nightly need is computed as max(0, need - slept) and summed, so a long night cannot cancel a short one. A net balance that does allow offsetting is reported alongside. Need is taken from the member's unrestricted sleep if given, otherwise their stated need, otherwise the midpoint of the National Sleep Foundation recommended range for their age band.
What it cannot do
- Sleep need is not directly measurable; the reference point is an assumption and dominates the error.
- Unrestricted sleep overestimates need in someone already in deficit, because it contains recovery sleep.
- Self-reported and wearable-estimated sleep duration both disagree with polysomnography, wearables typically in the direction of overestimating sleep.
- The literature does not support a one-for-one repayment model, so the cumulative debt figure should be read as an exposure marker rather than a balance owed.
- Duration is only one axis. Timing regularity, continuity and architecture all carry independent associations that this tool cannot see.
Sources
- Hirshkowitz M et al. National Sleep Foundation's sleep time duration recommendations. Sleep Health 2015;1(1):40-43DOI 10.1016/j.sleh.2014.12.010 (opens in a new tab)PMID 29073412 (opens in a new tab)
- Watson NF et al. Recommended Amount of Sleep for a Healthy Adult: AASM and SRS Joint Consensus Statement. Sleep 2015;38(6):843-844DOI 10.5665/sleep.4716 (opens in a new tab)PMID 26039963 (opens in a new tab)
- Van Dongen HPA et al. The cumulative cost of additional wakefulness. Sleep 2003;26(2):117-126DOI 10.1093/sleep/26.2.117 (opens in a new tab)PMID 12683469 (opens in a new tab)
- Klerman EB, Dijk DJ. Interindividual variation in sleep duration and its association with sleep debt in young adults. Sleep 2005;28(10):1253-1259DOI 10.1093/sleep/28.10.1253 (opens in a new tab)PMID 16295209 (opens in a new tab)
- Depner CM et al. Ad libitum Weekend Recovery Sleep Fails to Prevent Metabolic Dysregulation. Curr Biol 2019;29(6):957-967DOI 10.1016/j.cub.2019.01.069 (opens in a new tab)PMID 30827911 (opens in a new tab)
The formula version is pinned so that a result you saved or shared can be reproduced. When we change a coefficient, the version changes and old results stay attributed to the version that produced them.
Questions people ask
- Can I pay off sleep debt at the weekend?
- Only partly. In the controlled studies, ad-libitum weekend recovery sleep did not prevent the metabolic changes caused by a repeating pattern of weekday restriction. Consistency beats catch-up.
- How do you know how much sleep I need?
- We do not. In order of preference the tool uses your average on days with no alarm and no obligations, then what you tell us, then the midpoint of the National Sleep Foundation range for your age band. The result always states which of the three it used.