Straight answers about
your cycle.
Four subjects, because they are the four this site can speak on honestly: what happens to the data you hand a period app, how to choose what you hand it to, what actually happens in a cycle, and the practical life around one — first periods, products, school, sport and when something is worth a doctor's time. Every claim about a body is attributed to the NHS, ACOG, the NIH, a regulator or a peer-reviewed paper, with a live link on the page — and every claim about another app is quoted from that company's own published policy.
Privacy and your data
What period apps do with what you tell them, what the words in a privacy policy actually mean, and how to judge any tracker before you trust it with a year of your life.
All 9 pieces on thisThe Most Private Period Tracker: What Actually Protects You
Most privacy claims are promises. A few are architecture. This is how to tell which one you are being offered — and the seven questions that separate them.
Read it 9 min read · 7 sourcesWhat Data Do Period Apps Actually Collect?
Three layers of collection, and only one of them is the layer you chose. What a tracker holds, what it works out from that, and what a store privacy label can and cannot prove.
Read it 9 min read · 6 sourcesWho Can See Your Period Data? An Honest Map
Not a name, but a list of routes. The seven ways cycle data can reach somebody else, which of them your app leaves open, and the one that catches almost everybody.
Read it 9 min read · 6 sourcesPeriod Tracker Privacy Check: Judge Any App in Ten Minutes
Six checks, ten minutes, one score out of ten. The drill for judging any period app yourself — and an honest account of what it can and cannot tell you.
Read it 9 min read · 5 sourcesPeriod Tracking Without an App: The Paper Method That Still Works
One date a month, a pen and any calendar is a complete tracking system. Here is what to write down, how to read it back, and where paper genuinely loses.
Read it 9 min read · 7 sourcesHow to Delete Your Period Tracker Data — Properly
Deleting the app is the weakest of the three things people mean by deleting. Here is the order that reaches the copy a company holds, and what the published rules say about how long it takes.
Read it 9 min read · 7 sourcesDoes Deleting the App Delete Your Data? Usually Not
It depends entirely on whether there was an account, and if there was, the answer is no. What uninstalling really removes, and what has to be asked for separately.
Read it 9 min read · 6 sourcesAnonymous Period Tracking: What It Means, and What It Cannot Mean
One word covers three very different promises, and only one of them can be tested from the outside. Here is how to tell which you are being offered.
Read it 9 min read · 6 sourcesOffline Period Tracker vs Cloud Sync: The Honest Trade
Local-only removes the server, the account and the subpoena. It removes the backup with them. Here is the trade, argued against this site's own app.
Read itChoosing a tracker
Head-to-head reading on the apps people actually search for, on the two the phone already ships with, and on paper. Every statement about a named app comes from that company's own policy, and where nothing can be verified the page says so instead of guessing.
All 10 pieces on thisFlo Alternatives: Honest Options, Including the Ones That Are Not Apps
People leave Flo for four different reasons, and each one points at a different replacement. Here is the honest field, described only from what each company publishes about itself.
Read it 9 min read · 6 sourcesClue Alternative: What Changes If You Switch
Clue publishes a comparatively strict position on your data, so the useful question is what a move would actually gain you. Three real reasons to switch, what each one costs, and how to go without losing your history.
Read it 9 min read · 6 sourcesFlo vs Clue: What Each One Publishes About Your Data
A head-to-head built only from published, checkable statements. It compares documents rather than experiences, marks the questions neither company answers, and does not pick a winner.
Read it 8 min read · 5 sourcesApple Cycle Tracking: What the Health App Does, and What It Does Not
The period tracker already on your iPhone, judged on what Apple publishes about it. What it logs, what it predicts, what the deviation alert means — and the two things it cannot do for anyone.
Read it 9 min read · 6 sourcesPeriod Tracker Without an Account: What to Look For
An account is the mechanism by which your cycle data comes to live somewhere other than your phone. How to tell whether an app has one, and what going without honestly costs you.
Read it 9 min read · 6 sourcesPeriod Tracker Without a Subscription: What Free Actually Costs
Every way of funding an app leaves a fingerprint on the product. Here are the five ways a period tracker gets paid for, and how to work out which one is paying for yours.
Read it 8 min read · 6 sourcesPeriod Tracker Without Ads: Why the Business Model Is the Feature
An advert has to be aimed, and aiming it is what gives your data a reason to travel. How to read the store labels, and what "no ads" does and does not cover.
Read it 8 min read · 7 sourcesThe Best Period Tracker for Teens: A Privacy-First Answer
Early cycles are irregular for years, so a first tracker's job is memory, not prediction. Here is what to look for, what the store labels actually mean, and a short section for the parent reading over a shoulder.
Read it 8 min read · 6 sourcesOpen Source Period Trackers: What Being Open Actually Buys You
Open source turns a privacy promise into something somebody can check. That is worth a lot, and it is not proof — here is exactly where the line falls, and what drip and Euki actually say about themselves.
Read it 7 min read · 6 sourcesPaper vs App Period Tracking: An Honest Comparison
A notebook and a phone fail in different places. Compared on the axes that matter, with an honest verdict and the readers for whom paper alone is the better answer.
Read itUnderstanding your cycle
Straight answers about what a cycle is, what can be predicted, what cannot, what the four phases actually are, when a symptom is worth a doctor's time, and where the popular stories about the body came from.
All 22 pieces on thisWhen Will I Get My Period? What a Quiz Can and Can't Tell You
Every quiz that promises a date is guessing. Here is what the signs actually mean, what the timelines usually look like, and an estimator that gives you a range and admits it.
Read it 7 min read · 6 sourcesThe Moon and Your Menstrual Cycle: What the Research Actually Found
Two rhythms of about twenty-nine days, and a very old story about why. Here is what the studies actually found — including the ones that found nothing.
Read it 7 min read · 8 sourcesThe Menstrual Phase, Explained: What Is Actually Happening While You Bleed
Day one is the first day of full flow, and every number on this site is built on that one date. What the bleeding days are, what commonly comes with them, and where the ordinary ends.
Read it 7 min read · 7 sourcesThe Follicular Phase: The Half of Your Cycle That Does the Moving
The first half of the cycle is the part that stretches. What happens in it, why a long cycle is usually a long first half, and what that does to every date a calculator prints.
Read it 7 min read · 10 sourcesOvulation Explained: The Signs, the Timing, and What the Evidence Shows
Ovulation is a distribution, not a date. What each sign can genuinely see, how far ahead it sees it, and how strong the evidence under it is.
Read it 7 min read · 6 sourcesThe Luteal Phase: How Long It Really Lasts, and What Moves It
The textbook says fourteen days. The measurement says 12.4, with 18% of cycles under 11. What happens in the second half of a cycle, and how to work out your own.
Read it 6 min read · 7 sourcesCycle Length: What Is Normal, and What the Numbers Actually Say
Four respectable bodies, four different answers, all on one chart. Then the numbers from 612,613 real cycles, and what to do with your own.
Read it 7 min read · 8 sourcesIrregular Periods: When Normal Variation Is Worth a Conversation
Almost everybody thinks their periods are irregular, and most are describing ordinary movement. Here is what the word means to the NHS, to ACOG and to NICHD, and where each of them draws the line.
Read it 6 min read · 8 sourcesWhy Is My Period Late? The Ordinary Explanations, and the Ones to Check
A late period is nearly always a late ovulation, which is why the delay sits in the first half of the cycle. The ordinary explanations, in prose, for somebody who wants to understand rather than count.
Read it 8 min read · 9 sourcesPeriods After Stopping the Pill: What Comes Back, and When
What comes back is ovulation, and the period follows it. Here is what the NHS says by method, what one matched study measured, and the number nobody can honestly give you.
Read it 6 min read · 6 sourcesStress and Your Cycle: What Stress Can Actually Do to a Period
Stress is the explanation everybody reaches for, and it is both real and over-used. It moves the timing of a cycle; the studies that show that also show what it does not move.
Read it 7 min read · 6 sourcesPeriod Pain: What Is Normal, What Is Not, and When to Ask Someone
More than half of women who menstruate have some pain for a day or two each month. Here is the shape ordinary pain takes, the shape worth an appointment, and the thresholds the NHS puts between them.
Read it 8 min read · 6 sourcesPMS: What the Evidence Says About the Symptoms, the Timing and the Relief
PMS is defined by when symptoms arrive, not by which ones. Here are ACOG's criteria, the overlap nobody prints, and why two cycles of dated entries beat any symptom list.
Read it 8 min read · 6 sourcesPMDD: An Honest Overview of Premenstrual Dysphoric Disorder
A recognised condition, the diagnostic criteria a clinician actually applies, prevalence figures that disagree with each other, and the NHS's emergency advice printed high rather than buried.
Read it 7 min read · 7 sourcesHeavy Periods, Honestly: What Counts as Heavy and What to Do About It
Nobody can see anybody else's period, so heavy usually gets judged against friends who are also guessing. The NHS answers it with seven concrete tests, and this page prints all seven.
Read it 6 min read · 6 sourcesSpotting Between Periods: The Honest List of What Causes It
Blood you were not expecting has a long list of causes, ordinary and serious, and the bleeding itself does not tell them apart. The urgent exception first, then the honest list.
Read it 7 min read · 6 sourcesYour Cycle and Sleep: What Changes, What Does Not, and What Helps
Reported sleep gets worse before a period; measured sleep barely moves. What that gap means, what does change in the laboratory, and why none of it says the tiredness is imaginary.
Read it 8 min read · 6 sourcesYour Cycle and Exercise: What the Evidence Supports, and What It Does Not
A meta-analysis of 78 studies found a trivial effect and refused to write guidelines. An umbrella review found no strength difference in 9 of 10 quality studies. Here is what that leaves you with.
Read it 8 min read · 6 sourcesBBT Charting: How to Take a Basal Body Temperature and Read the Chart
The method done properly, and its ceiling in the same breath. A temperature chart records what has already happened — and against hormone-confirmed ovulation across 193 cycles, the shift showed up in under a quarter of them.
Read it 7 min read · 6 sourcesCervical Mucus Tracking, Honestly: What It Shows and What It Cannot
The one sign that looks forwards, with both of its numbers. Beginners identified a peak day in 63% of cycles; the figure everybody quotes comes from women who had been taught. That gap is the article.
Read it 6 min read · 9 sourcesThe First Ovulation After Periods Start: What the Early Years Look Like
A period is not proof that an ovulation happened. Half of all cycles in the first two years are anovulatory even when they arrive on time — what the early years look like, and the two numbers worth carrying.
Read it 6 min read · 12 sourcesPeriod Myths, Debunked: Fifteen Things That Are Not True
Fifteen things repeated everywhere that the evidence does not support — the 28-day cycle, day-14 ovulation, the fixed second half, the Moon — each with the correction and the study it came from.
Read itFirst periods and practical life
The practical half of having periods: the first one, what to say to a parent, what the products actually are, school, sport, leaks, cost, and how to tell the difference between something ordinary and something worth ten minutes of a doctor's time. Written plainly, for someone who may be eleven, and sourced the same way as everything else here.
All 19 pieces on thisYour First Period: A Complete Guide to the Day and the Year After
It is far less blood than you are expecting, every kind of product is safe from the first day, and the year that follows is meant to be untidy. Here is the day, the hour after it, and the two lines worth knowing.
Read it 5 min read · 5 sourcesHow to Tell a Parent About Your Period: What to Say, and When
Six words will do it, and you can send them as a text. Scripts for saying it, an option for when a parent is not the easiest adult, and the two things you actually need from one.
Read it 9 min read · 8 sourcesPeriod Products Explained: Pads, Tampons, Cups, Discs and Period Underwear
Five kinds of product and no order of merit. Here is what each one is, how much each one holds, and the long list of things — comfort, ease, which one suits somebody starting out — that nobody has ever measured.
Read it 7 min read · 6 sourcesHow to Use a Tampon: A Plain Guide, and the Safety Part Told Straight
The NHS describes a tampon in about three lines, and the rumour about toxic shock is much longer than the evidence. This page prints the symptoms, the emergency line and the measured numbers, and refuses to invent the one figure everybody else gives you.
Read it 8 min read · 7 sourcesMenstrual Cups, Honestly: What Forty-Three Studies Actually Found
Forty-three studies sounds like settled science. Only three of them were of moderate-to-high quality — so here is what they found, with that caveat attached to every number.
Read it 7 min read · 5 sourcesPeriod Underwear, Honestly: How Much It Actually Holds
The most marketed period product has the least measurement behind it. One trial of twenty people is the whole evidence base, and its most useful finding is a warning rather than a review.
Read it 5 min read · 5 sourcesSwimming on Your Period: What Works, and What Nobody Has Actually Studied
The question everybody types has no citable answer, and that is worth saying out loud rather than filling in. What can honestly be stated here is short; the rest is a rule somebody invented and nobody ever checked.
Read it 7 min read · 6 sourcesSport and Your Period: What the Research Says About Training and Competing
For the fixture that lands on a bad day, the coach who wants a plan, and the training group where everybody has a theory. Plus the two NHS lines that people good at ignoring their bodies walk straight past.
Read it 7 min read · 5 sourcesPeriods at School: The Kit, the Toilets and the Awkward Bits
Nearly every school problem is one of three: no pad on you, a lesson you cannot leave, or pain in the middle of one. A kit you pack once, and the NHS line on who to ask when you have nothing.
Read it 7 min read · 6 sourcesPeriod Leaks: How to Make Them Less Likely, and What to Do in the Moment
A saturated super pad holds about 5ml. A whole period is 20 to 90ml. That is the entire explanation — and then the part nobody writes down, which is what to do in the ten minutes after it happens.
Read it 7 min read · 6 sourcesHow Much Does a Period Cost? Honest Arithmetic, and What Nobody Has Measured
Every page ranking for this question prints a grand total built on invented assumptions. This one shows the arithmetic, prints the single published price range, and leaves the slots only you can fill blank.
Read it 8 min read · 8 sourcesTracking Your First Year of Periods: What to Write Down and What to Ignore
A messy first year is the expected result rather than a fault. Here is the one thing worth writing down, the things that are not, and the two thresholds that are worth an appointment.
Read it 8 min read · 8 sourcesTalking to a Doctor About Your Periods: What to Bring and What to Say
Bring dates, and say what your periods stop you doing. Those two things turn a vague ten minutes into a useful one — and neither needs you to know anything medical.
Read it 8 min read · 8 sourcesIs My Period Normal? Clots, Colour, Length and the Things That Look Alarming
Most of what looks alarming is ordinary, and each one has a line where it stops being ordinary. Here are both halves, with the NHS's own numbers attached.
Read it 8 min read · 9 sourcesWhen to See a Doctor About Your Period: The Thresholds, Not the Worry
Three different speeds, and telling them apart is most of the answer. Every line here is quoted from the NHS or ACOG, and almost all of them are an ordinary appointment.
Read it 7 min read · 6 sourcesPeriods and Sleep for Teenagers: What Actually Changes and What Does Not
Bad nights and bad periods turn up in the same girls. The one study of the right age group says it cannot tell you which is causing which — and that honest answer is more useful than the confident one.
Read it 7 min read · 6 sourcesPMS in Teenagers, or Just Being a Teenager? How Anyone Actually Tells
The symptom list cannot separate PMS from an ordinary bad fortnight, because everything on it belongs to both. What separates them is where the bad days land — and that is only visible going forwards.
Read it 7 min read · 9 sourcesDo Periods Sync With the Moon? And Five Other Things You Will Hear at School
The lunar month is about 29.5 days and the average cycle about 29, so half of everybody bleeds near a full moon by chance. That, and five more corridor stories with the numbers put back in.
Read it 6 min read · 6 sourcesPE and Periods: Getting Through Gym Class Without Dreading It
The research does not support sitting out: pooled across 78 studies the effect was trivial and the interval crossed zero. That is not the same as "so stop complaining" — pain is real, and this page covers both halves.
Read itHow this writing is done. Sources are limited to the NHS, ACOG, the NIH, the FTC, the ICO, the California Attorney General and peer-reviewed papers on PubMed Central. Every URL is opened and read before it is cited, and the citation carries the publisher, the year and the bare link so you can check it in one click.
When a page names another app. Everything said about a named tracker comes from that company's own privacy policy or support page, quoted as what the company says rather than as something we have verified. No feature is described from memory, no price is quoted, and no page stands on marketing alone — a comparison always cites a health publisher or a regulator as well.
What is not here, on purpose. No cycle-syncing protocols, no predicting a baby's sex, no "safe days", no diagnosis. Where an accurate sentence and a popular search phrase pull in different directions, the accurate sentence wins and the page finds another way to answer the question. Several widely repeated numbers were cut from these pieces during checking because no source supports them.
None of it is medical advice, and none of it replaces someone who knows your history.
Free cycle tools
Period Calculator
Your last period plus your usual cycle length, six cycles laid out on the moon ring, and the whole thing as a printed calendar or a calendar file — windows, never single days.
Open itCycle Length Calculator
Log a few period start dates and read your own numbers: average, shortest, longest, and how much the whole thing moves.
Open itPeriod Late Calculator
How late is late, measured against your cycle rather than a textbook one — plus the ordinary explanations, and the day a test would actually mean something.
Open itCycle Phase Calculator
Which phase you are probably in today, what is actually happening in it, and a straight answer about how blurred the edges between them are.
Open itOvulation Calculator
The days ovulation is most likely, worked backwards from your next period — printed as a window, because a single day would be invented.
Open itOvulation Test Calculator
Which day to start an ovulation test, how many days to keep going, and a straight answer about what a positive one does and does not mean.
Open itLuteal Phase Calculator
The days from ovulation to your next period — counted exactly when you know the date, and estimated with the uncertainty shown when you do not.
Open itImplantation Calculator
The days implantation is most likely, straight from the study that measured it — and an honest account of what cramping and spotting can and cannot tell you.
Open itPregnancy Test Calculator
Three ways in — ovulation, conception, or your last period — and two dates out: the earliest a test is worth taking, and the day its answer can be trusted.
Open itPrintable Period Tracker
Build a paper tracker for any month or a whole year, then print it. Flow key, symptoms, an optional temperature row — and a gentler version for a first tracker.
Open itPrintable Period Symptom Tracker
A month across the top, your symptoms down the side, one box a day. Rename every row, print one page, and bring the pattern to the appointment.
Open itPrintable BBT Chart
Graph paper for a cycle: a temperature grid in °C or °F, a row for the coverline, and space for the notes that make a chart readable later.
Open itFirst Period Kit Checklist
What to put in a school bag and what to keep at home, on one printable page. Editable, unfussy, and written to be reassuring rather than dramatic.
Open itAthena keeps all of this on your phone.
A calculator answers the one question you brought it. Athena is the same arithmetic living on your device — the moon ring, an honest calendar with ranges instead of false precision, and a database that never leaves the phone because there is no account and no server behind it.
On the App Store and Google Play, for iPhone and Android.
What Athena is