About Sleep Sums

Sleep Sums is a set of free sleep calculators: what time to go to bed or get up, how many cycles you slept, how much sleep you owe, when to nap, when to stop drinking coffee, and how to get over jet lag. Each one is built on a published guideline or a measured physiological rate, and each page explains the reasoning rather than asking you to trust a number.

Where the numbers come from

Sleep need by age follows the National Sleep Foundation consensus (Hirshkowitz et al., 2015) and the American Academy of Sleep Medicine paediatric consensus (Paruthi et al., 2016). Bedtime and wake-time targets use the roughly 90-minute sleep cycle and a 15-minute sleep-onset allowance, the midpoint of the 10-20 minute normal range. Stage proportions (light, deep, REM) are typical adult polysomnography averages. Caffeine uses the roughly five-hour elimination half-life the FDA cites, its 400 mg daily guideline, and the American College of Obstetricians and Gynecologists' 200 mg limit in pregnancy; the sleep-impact figures come from Drake et al. (2013). Jet lag uses the re-entrainment rates in Waterhouse et al. (Lancet, 2007) of about one hour a day eastward and one and a half westward, with light and melatonin timing per Eastman and Burgess (2009). Where a number is a rule of thumb, such as the 90-minute cycle, the page says so and gives the real range.

What this site doesn't do

It doesn't store what you enter, require an account, or diagnose anything. Sleep cycles vary from 70 to 120 minutes between people and across the night, so a cycle-based bedtime is a good default, not a precise target. Persistent insomnia, loud snoring, gasping during sleep, or sleepiness that affects driving are medical questions for a doctor or a sleep clinic, and no calculator here replaces that.

Corrections

If you are a sleep clinician or researcher and a guideline, rate or threshold here is out of date, email hello@sleepsums.com. Sources are named on each page so a correction can be checked against them.