Period Tracker
Track your menstrual cycle, predict your next period, and identify patterns. Sync across devices with cloud save.
Log your period start dates to track cycles and predict future periods.
This tool is for informational purposes only and should not replace professional medical advice. Always consult your healthcare provider for medical decisions. Cycle tracking is more accurate with 6 months of data.
Why Tracking Beats Guessing
Most adults can name their average cycle length to within a few days, but very few can predict when their next period will arrive without help. Logging the start date of each period over 3-6 cycles gives you an actual average, an actual minimum and maximum, and a reasonable next-period prediction. The tracker saves your data locally so it persists between visits, and once you have logged at least two cycles it works out the gap between them automatically.
A healthy adult menstrual cycle ranges from 21 to 35 days according to the NHS, with the average around 28 days. Cycles outside that range, or that vary by more than 7-10 days, are worth mentioning to your GP. Period length is typically 3-7 days; anything longer than 8 days or heavy enough to soak through a pad or tampon every hour is also worth a conversation with your GP.
What Your Cycle Pattern Suggests
| Pattern | What it might mean |
|---|---|
| Cycles 21-35 days, varying by less than 5 days | Healthy regular cycle |
| Cycles consistently under 21 days | Possibly polymenorrhoea or short luteal phase, see GP |
| Cycles consistently over 35 days | Possibly oligomenorrhoea, PCOS, or thyroid issue |
| Variation over 10 days month to month | Irregular cycle, worth investigating |
| Skipped periods (over 90 days) | See GP within a month, particularly if not pregnant |
| Sudden change from a previous pattern | Always worth mentioning to GP |
Using Cycle Data Beyond Period Prediction
Once you have logged 3-6 cycles, the tracker estimates not just your next period but also your next likely fertile window (typically days 9-14 of a 28-day cycle, scaled to your average). For trying to conceive this is useful as a baseline; for general health it helps you anticipate energy dips, mood changes, and PMS. Many women plan demanding work, social events, or holidays around their cycle once they know it, which makes the tracking habit worthwhile even outside of fertility planning.
If you spot patterns you do not like (severe PMS, painful periods, very heavy flow, mid-cycle pain that is not just ovulation), bring the tracking data to your GP. Showing 6 months of logged cycles is far more useful than trying to remember from memory. If you suspect pregnancy, the [pregnancy due date calculator](/pregnancy-due-date-calculator) takes your last period date as its starting point.
Frequently Asked Questions
How many cycles should I track before predictions are reliable?
Two cycles minimum to get any prediction, six for genuine reliability. With two cycles the tracker has one cycle length to work with; the next-period prediction is essentially that one length added to your last period. With six cycles it has a real average and can spot whether one cycle was an outlier.
Is my data sent anywhere?
By default, your tracking data is saved only to your browser's localStorage on this device. It is not sent to any server, and clearing your browser data will delete it. If you sign in with a MyKit account, the data syncs to your account so you can access it from other devices, but it remains private to you.
What does it mean if I miss a period?
Pregnancy is the most common cause for sexually active women of reproductive age, so take a home test first. Other common causes include stress, significant weight change, intense exercise, hormonal contraception changes, thyroid issues, PCOS, and perimenopause. The NHS recommends seeing your GP if you miss three periods in a row, or sooner if you have additional symptoms like pelvic pain or unusual discharge.
Can a tracker really help with fertility?
It can give you the cycle data you need to spot your fertile window, but it cannot replace ovulation predictor kits, basal body temperature charting, or a GP fertility assessment. If you have been trying to conceive for over a year (or 6 months if you are over 35), please book a GP appointment. The cycle data you have logged will be useful information for them.
Related Tools
Ovulation Calculator
Calculate your predicted ovulation date based on your menstrual cycle. Identify your fertile window for planning or avoiding pregnancy.
Irregular Cycle Ovulation Estimator
Estimate ovulation with an irregular menstrual cycle using statistical analysis of your cycle history.
Pregnancy Due Date Calculator
Calculate your estimated due date from your last period or conception date. Track trimester milestones, weeks pregnant and days remaining