Tonight’s plan
Lights-out target, wake window and caffeine cutoff from your actual day.
HesperaSleep calculator for iPhone & Android
The sleep calculator that plans the night before the night plans you.
Tonight’s bedtime, wake window and caffeine cutoff — worked out from the day you actually had. No wearable needed.
Night architecture
Night architecture
What Hespera gives you
A practical sleep system, not another wellness feed.
Caffeine curve
Every drink decays against bedtime — see what’s still in your system.
Sleep debt ledger
Short nights accumulate and repay over days. Visible before the crash.
Energy forecast
Tomorrow as windows and dips, not a fake precision score.
Morning close-out
Confirm, correct or skip the night in seconds. History stays honest.
Evidence, not vibes
Charts unlock only when there’s enough signal to mean something.
How it works
Four steps, every night.
Most bedtime calculators ask one number and hand back times spaced 90 minutes apart. Hespera runs the same arithmetic, then corrects it with the things that actually move your bedtime.
Want the maths right now? Try the free web calculator — no download.
Log the day you actually had
Coffee with its timing, naps, stress, screens, workouts. Ten seconds in the evening, no wearable.
It counts the night backwards
From the morning you need, through full sleep cycles, plus the time you personally take to fall asleep.
You get a window, not a minute
A lights-out target, a wake window and a caffeine cutoff — precise enough to act on, honest about the rest.
The morning corrects the maths
A quick close-out keeps your history true, so tomorrow’s plan runs on your real data instead of guesses.
Free web tools
Try a slice of it in your browser.
Why it helps
It keeps noisy nights from becoming fake insight.
Missed nights stay gaps, not fake zeros. Habits only get named once the pattern repeats. “Sleep better” becomes a set of decisions instead of a vibe.
sleep debtenergy forecastcaffeine curvenight qualitywake rhythmweek shape
FAQ
Questions before trying Hespera.
What does Hespera do?
Hespera is a sleep calculator and bedtime planner. It turns the caffeine, naps, stress and exercise of your actual day into tonight’s bedtime, wake window and wind-down, then tracks sleep debt and energy as your history builds up.
How does the Hespera sleep calculator work?
It starts from the morning you need, counts back through full sleep cycles, adds the time it usually takes you to fall asleep, and checks what caffeine is still in your system at that point. The result is a lights-out target and a wake window rather than one exact minute.
Can I use it as a sleep cycle calculator?
Yes. The bedtime and wake window Hespera calculates are aligned to complete sleep cycles, so you are less likely to be woken in the middle of deep sleep. Unlike a fixed 90-minute web calculator, it also accounts for how long you personally take to fall asleep.
Does Hespera calculate nap timing and wake windows?
Naps are one of the factors you log, and they change the plan: an afternoon nap moves tonight’s lights-out target and the wake window that follows it. The recovery plan lays out morning light, last coffee, nap, wind-down, bedtime and wake time as one sequence.
How does Hespera calculate sleep debt?
Short nights accumulate against what you actually needed and repay over several days, all kept in the same local-day frame as your caffeine and wake times. That is what makes debt readable as part of the week instead of a disconnected number.
How does caffeine change the bedtime it calculates?
You log coffee, tea and energy drinks with the time you drank them, and each one decays against your bedtime. Hespera can then show what may still be disrupting deep sleep and suggest a caffeine cutoff that fits your schedule rather than a generic "no coffee after 2pm" rule.
Is Hespera a sleep tracker or a sleep diary?
It is a sleep planner first, with a sleep diary underneath it. You close each night out in the morning — confirming, correcting, or skipping it — so the log stays honest and the calculations that follow stay useful.
Does Hespera work without a wearable?
Yes. Hespera is built around quick check-ins and corrections rather than sensor data, so it stays useful when a night has to be entered by hand. You do not need a watch, a ring or a smart mattress.
What if my schedule is irregular?
The plan is recalculated from the day you actually had rather than from a fixed routine, so a shifted or messy day produces a different bedtime instead of the same reminder. Nights you would rather not count can be skipped so they never distort your history.
Is Hespera free?
Yes. Hespera is free to download on the App Store (iPhone, iOS 15 or later) and on Google Play (Android). No subscription is needed to use the planner.
Make tonight less random.
Built for people who want better sleep without turning bedtime into homework.