Sleep midpoint chronotype calculator
Enter when you fell asleep and when you woke to get the clock exactly halfway through your night: 23:00 to 07:00 is eight hours with a midpoint at 03:00, an intermediate chronotype. Nights that cross midnight are handled for you. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Bedtime
- 23:00
- Wake time
- 07:00
- Sleep duration minutes
- 480
- Sleep duration hours
- 8
- Midpoint
- 03:00
- Midpoint minutes
- 180
Chronotype research often uses the midpoint of sleep—the clock time halfway between sleep onset and wake—as a compact marker of whether someone runs earlier or later on the day. This sleep midpoint chronotype calculator takes a bedtime and a wake time in twenty-four-hour HH:MM form, measures the sleep interval with correct midnight wrapping, places the midpoint at half that duration, and returns a simple early, intermediate, or late label based on where that mid-sleep clock falls. No sensors, no account, no network, and no system clock are involved: only the two times you send.
What sleep midpoint means and how chronotype bins are assigned
The sleep midpoint is the wall-clock moment that sits exactly halfway between the start of sleep and the moment of waking. If you fall asleep at twenty-three hundred and wake at seven hundred, the interval is eight hours and the midpoint is three o’clock in the morning.
That single clock is widely used in chronobiology as a practical proxy for chronotype—the tendency to be a morning type, an intermediate type, or an evening type—because it compresses both bedtime preference and wake preference into one number without requiring a full questionnaire on every check. Chronotype is then binned only from that midpoint clock: early when the midpoint falls before three o’clock, intermediate from three o’clock inclusive until five o’clock exclusive, and late from five o’clock onward.
Those thresholds are planning heuristics inspired by mid-sleep distributions in free-day research, not a clinical diagnosis. People with irregular shifts, jet lag, or sleep disorders should follow clinical advice; for everyday self-tracking and product features, a stable mid-sleep marker remains one of the simplest ways to talk about earlier versus later schedules without inventing proprietary scores.
Who uses the sleep midpoint, and how
Wellness apps and coaching bots need a tiny offline-safe primitive that turns two user clocks into a mid-sleep marker without shipping a full Munich ChronoType Questionnaire implementation or calling a cloud model. Research notebooks and classroom demos can batch many bedtime and wake pairs to illustrate how shifting either end of the night moves the midpoint and the early versus late label.
Content sites that rank for sleep midpoint calculator or chronotype mid-sleep time benefit from a free browser path that matches the paid automation path byte-for-byte on the same pure module, so marketing demos and production jobs never disagree.
What you can do with it
Personal chronotype self-check
Enter last night’s bedtime and this morning’s wake time to see your mid-sleep clock and whether it falls in the early, intermediate, or late bin.
Teaching and batch schedule tables
Generate midpoints for many bedtime and wake pairs in notebooks or content tools to show how schedule shifts move chronotype markers.
FAQ
How are early, intermediate, and late assigned?
From the midpoint clock only: early if before 03:00, intermediate from 03:00 up to but not including 05:00, and late from 05:00 onward.
What does my sleep midpoint say about my chronotype?
It folds your bedtime and wake preferences into a single clock. Chronobiology uses it as a practical proxy for whether you are a morning, intermediate or evening type, without filling in a full questionnaire every time.
Does it work if I fall asleep before midnight and wake after?
Yes. A wake time that is not later than the bedtime is treated as the next day. That is why 23:00 to 07:00 gives eight hours of sleep and a midpoint at 03:00.
What time format should I use?
Use the 24-hour clock, from 00:00 to 23:59, such as 23:00 or 06:30. Twelve-hour times with AM or PM and bare numbers are rejected rather than guessed.
Is the chronotype label a medical diagnosis?
No. The cut-offs are planning guides inspired by research on sleep during days off work. If you work irregular shifts, have jet lag or live with a sleep disorder, follow the advice of a clinician.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/health/sleep-midpoint \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"bedtime":"23:00","wake_time":"07:00"}'const res = await fetch("https://api.kit.forhosting.com/health/sleep-midpoint", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"bedtime": "23:00",
"wake_time": "07:00"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/sleep-midpoint",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"bedtime": "23:00",
"wake_time": "07:00"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/sleep-midpoint", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"bedtime":"23:00","wake_time":"07:00"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"bedtime":"23:00","wake_time":"07:00"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/sleep-midpoint", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"bedtime": "23:00",
"wake_time": "07:00"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.sleep_midpoint",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Missing fields, non-string values, and malformed clocks fail with invalid_input instead of inventing a midpoint.
What sleep midpoint means and how chronotype bins are assigned
This capability models that idea with a fixed, transparent rule: convert bedtime and wake_time to minutes since midnight, treat a wake clock that is not strictly later than bedtime as belonging to the next calendar day, compute duration as wake minus bed, then add half the duration to bedtime and wrap modulo one thousand four hundred forty minutes to obtain the midpoint HH:MM string.
Input contract, validation, response shape, and worked example
Each must match a strict twenty-four-hour pattern from 00:00 through 23:59, for example 23:00 or 06:30. A later pair such as 01:00 to 09:00 yields midpoint 05:00 and chronotype late. An early pair such as 21:00 to 05:00 yields midpoint 01:00 and chronotype early. POST a JSON body with two required string fields: bedtime and wake_time. Twelve-hour strings with AM or PM, bare numbers, empty strings, missing keys, and non-string values are rejected with invalid_input that names the field, and those failures are not billed. On success the body echoes the normalized zero-padded bedtime and wake_time, reports sleep_duration_minutes as an integer minute count, sleep_duration_hours as a short decimal, midpoint as HH:MM, midpoint_minutes as minutes since midnight for easy charting, chronotype as one of early, intermediate, or late, and a formula string restating the half-interval rule with midnight wrap. Example: bedtime 23:00 and wake_time 07:00 yields sleep_duration_minutes 480, sleep_duration_hours 8, midpoint 03:00, midpoint_minutes 180, and chronotype intermediate, because half of eight hours after twenty-three hundred lands at three in the morning. Pair the response with your own local labels if you need weekday free-day annotations; this endpoint only reasons about the two wall clocks you provide.
Where a sleep midpoint chronotype API earns its keep
API automation at $0.002 per successful call lets planners generate tables across many hypothetical schedules—for example sliding bedtime earlier by fifteen minutes while holding wake fixed—while invalid input never consumes balance. Treat the early intermediate late thresholds as transparent product defaults you can re-bin client-side from midpoint_minutes if your study protocol uses different cut-points; the hard contract is the deterministic midpoint arithmetic, which is what goldens pin and what users can recompute by hand.
Integration use cases
Wellness app mid-sleep marker
Call the API from a sleep diary feature so each logged night stores a stable midpoint and chronotype label without on-device science models.
Technical questions
How is sleep midpoint calculated?
Convert bedtime and wake_time to minutes, wrap wake to the next day if it is not after bedtime, take duration = wake − bed, then midpoint = bedtime + duration / 2, formatted as HH:MM.
What if I sleep across midnight?
That is the normal case. If wake_time is not strictly later than bedtime on the same day, the interval is treated as crossing midnight automatically.
What inputs are rejected?
Missing bedtime or wake_time, non-string values, empty strings, and any clock that is not a valid 24-hour HH:MM between 00:00 and 23:59 fail with invalid_input and are not billed.
What does the sleep midpoint chronotype calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.