HesperaSleep guides
The science behind the calculators.
Everything Hespera computes rests on published sleep research. These guides walk through that research in plain language — real studies, real numbers, honest about what’s still uncertain.
How much sleep do you actually need?
The official numbers by age, the study that settled the 6-hour question, and a two-week method to find your own number.
Read the guide →Sleep cycles, explained
N1 to REM, what each stage does, and why the famous 90-minute cycle actually runs anywhere from 60 to 150.
Read the guide →Sleep debt: can you actually catch up?
Two weeks at 6 hours impairs you like an all-nighter — and you won’t feel it. What repayment really costs.
Read the guide →Caffeine and sleep
A 3 PM coffee is still arguing with you at midnight. The trials that put real numbers on “too late.”
Read the guide →Why do I wake up tired?
Sleep inertia, social jetlag, alcohol, apnea — how to tell a normal foggy morning from a symptom.
Read the guide →Prefer doing to reading? Start with the free tools: the sleep calculator, the nap calculator, the sleep debt calculator and the caffeine calculator.
From reading to doing
The app is these guides, running on your real days.
Hespera turns the research above into a nightly loop: log the day in seconds, get a lights-out target and wake window, close the night out in the morning — and let the patterns surface with evidence behind them.