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Cycle calendar
Next periods and the fertile window — a projection, not contraception.
It runs entirely in this browser tab: what you type is never uploaded, and the tool makes no network request while it works. Open your browser's network panel and try it — nothing leaves the page. There is no sign-up and no account.
What it takes
- Start
- A date.
- Cycle length (days)
- Optional.
- Luteal phase (days)
- Optional.
- Period length (days)
- Optional.
An example
start = 2024-03-04
length = 28
Settings
- Month before day
- Only for a date like 03/04 — a four-digit year first is never ambiguous.
- Cycles to draw
- How many months forward the calendar runs. A number from 1 to 12.
How to use it
- Fill in the boxes above. Anything you leave blank the tool works out.
- Adjust the settings beside it until the result is what you wanted.
- Copy the result, or save it as a file. The result updates as you type.
Questions
- Is this medical advice?
- No. It is arithmetic on the numbers you supplied, with the formula named, and it says so on every result. Nothing here diagnoses or prescribes.
- Where do the numbers in the formula come from?
- From published equations, each named on the result, and from whatever you typed. Nothing is looked up: there is no drug database, no national schedule and no reference range invented to fill a gap. Where a tool has no answer it says so with the reason.
- Is what I type uploaded anywhere?
- No. This page carries the whole tool as WebAssembly and runs it on your own device. Nothing you type is sent anywhere, which for a health calculator is the point rather than a feature.
- Is there a version that is not a web page?
- Yes. The same tools are built as a desktop application from the same code, with a save dialog instead of a download and no network code at all.
Other tools for daily
Daily water
A range from body mass, exercise and heat — not eight glasses.
Sleep cycles
What time to go to bed, counted in whole cycles.
Sun exposure
Time to a burn by skin type, and what a bottle really buys.
Vaccination dates
Your card's intervals turned into dates. No national schedule is shipped.
All thirty-two tools