Menstrual cycle tracker and period due date calculator
The menstrual cycle tracker counts from the first day of bleeding, day one, through the day before the next bleed. The period due date calculator adds your average cycle length to the last period date: a 28-day cycle starting 1 September predicts 29 September, a 30-day cycle predicts 1 October, and a 26-day cycle predicts 27 September. Cycle length calculator logic clamps inputs to 21 to 60 days and treats the average of your last three to six cycles as the best input. Single-cycle blips from travel or illness matter less than the rolling average your history table builds automatically.
Ovulation period predictor, cycle length and fertile window
Ovulation lands about 14 days before the next period regardless of cycle length, so the ovulation period predictor subtracts 14 from the predicted date: 29 September minus 14 gives 15 September for the standard example. Longer 35-day cycles ovulate near day 21, shorter 24-day cycles near day 10. The fertility window with period spans five days before ovulation plus ovulation day and the day after, because sperm outlive the egg. The intensity timeline peaks at ovulation and shades the fertile band, turning abstract subtraction into a visible planning strip.
Irregular period tracker and next period date chart
Irregular period tracking replaces single-day promises with ranges. If cycles swing 26 to 34 days, the next bleed window spans eight days and the fertile band widens correspondingly. Variation under 7 to 9 days across cycles is common with stress, exercise shifts, weight change or perimenopause. The next period date chart draws the full cycle with menstrual, follicular, ovulation and luteal phases proportioned to your length, so patterns emerge across months. Log every start date honestly, including spotting notes, and the history under vc-history-period-calculator becomes a record worth showing your clinician.
How late can a period be and how ovulation is derived
A period up to 7 days late with a previously regular cycle often reflects delayed ovulation rather than a missed cycle, and a test after the seventh late day is most reliable. Periods repeatedly beyond 35 days apart, bleeding between periods, soaking protection hourly, or three missed months deserve medical review. Ovulation from last period is always derived backwards from the next expected bleed, never forwards from the last one alone, which is why cycle length accuracy decides everything. Confirm persistent irregularity with labs and scan rather than calendar tweaks.
History, PDF and privacy-first tracking
Every prediction saves locally with LMP, cycle, next date and ovulation, drawing continuity no account system can match without uploads. The Download Cycle Report button embeds both charts, inputs, phase splits and disclaimers into a branded PDF for appointments. Large date inputs, bottom tabs and dark-mode visuals keep daily checks effortless, and reduced motion is respected throughout. Share buttons and related vitals tools link to pregnancy dating when a test turns positive, plus hydration and BMI for broader wellness. This tool is for educational purposes only and is not a substitute for professional medical advice. Always consult your doctor for diagnosis, contraception or fertility planning.
Worked examples to verify
Check the math: last period 1 September with 28 days gives next 29 September and ovulation 15 September, matching our accuracy suite. A 32-day cycle from the same start gives next 3 October and ovulation 19 September. A 24-day cycle gives next 25 September and ovulation 11 September. Fertile windows open five days before each ovulation date. Run your own numbers twice with neighboring cycle lengths to feel the sensitivity before relying on any single prediction.
Cycle phases explained with day counts
Menstruation typically spans days 1 to 5 when the uterine lining sheds. The follicular phase overlaps from day 1 until ovulation as follicles mature and estrogen rises. Ovulation itself lasts roughly 24 hours near the cycle-minus-14 mark, with the two-day fertile peak around it. The luteal phase then runs a stable 14 days of progesterone dominance before either implantation or the next bleed. In a 28-day cycle that reads 5 menstrual, 9 follicular-only, 2 ovulatory and 12 luteal-plus days, while a 35-day cycle stretches the follicular portion to 16 days with the luteal phase unchanged. The phase pie redraws these proportions for every length you enter.
Contraception, fertility planning and record keeping
Calendar predictions alone cannot serve as contraception because ovulation shifts with stress and illness, and sperm survival extends risk across days. Couples planning pregnancy should target the full six-day fertile window rather than a single date, confirm with ovulation kits or temperature when precision matters, and log attempts beside predictions. Keep three to six months of start dates in history before judging regularity, export the cycle report PDF quarterly, and carry it to gynecology visits with symptom notes on flow, pain and spotting for faster diagnosis.