Menstrual Cycle TrackerOvulation & Fertile DaysMulti-Month Projections

Period Calculator

Calculate your next menstrual period dates, bleeding duration, estimated ovulation day, and fertile windows across future months based on your cycle history.

100% Free Health Tool•Accurate Cycle Forecast•Color-Coded Timeline

Menstrual Details

First Day of Your Last Period (LMP):

Period Bleeding Duration (Days):

Number of days bleeding typically lasts each cycle.

Average Length of Menstrual Cycles:

Days from the first day of one period to the day before your next period starts.

Cycle Rhythm Tip:

Logging the exact first day of bleeding each month helps detect subtle irregularities and improves prediction accuracy for upcoming travel, events, and fertility windows.

Next Menstrual Period

In 28 Days

Next Expected Period Dates:

Oct 10 – Wed, Oct 14, 2026

Duration: 5 days•Cycle Length: 28 days

Next Estimated Ovulation

Sat, Sep 26, 2026

Day 14 of cycle

Next Fertile Window

Sep 21 – Sep 27

6-day conception span

Multi-Month Period & Ovulation Schedule:

6 Cycles

Cycle	Expected Period	Ovulation	Fertile Window
1Cycle 1	Oct 10 – Oct 14	Sat, Oct 24, 2026	Oct 19 – Oct 25
2Cycle 2	Nov 7 – Nov 11	Sat, Nov 21, 2026	Nov 16 – Nov 22
3Cycle 3	Dec 5 – Dec 9	Sat, Dec 19, 2026	Dec 14 – Dec 20
4Cycle 4	Jan 2 – Jan 6	Sat, Jan 16, 2027	Jan 11 – Jan 17
5Cycle 5	Jan 30 – Feb 3	Sat, Feb 13, 2027	Feb 8 – Feb 14
6Cycle 6	Feb 27 – Mar 3	Sat, Mar 13, 2027	Mar 8 – Mar 14

Complementary Women's Health & Fertility Calculators:

Ovulation Calc

Conception Calc

Pregnancy Calc

The 4 Phases of the Menstrual Cycle: Physiology & Hormones

1. Menstrual Phase (Days 1–5)

Estrogen and progesterone drop if fertilization does not occur, triggering the shedding of the uterine endometrial lining as menstrual fluid.

2. Follicular Phase (Days 1–13)

Follicle-Stimulating Hormone (FSH) stimulates ovarian follicles to develop. Developing follicles secrete estradiol, rebuilding the endometrium.

3. Ovulatory Phase (Day 14)

A sharp surge in Luteinizing Hormone (LH) causes the dominant follicle to rupture, releasing a mature oocyte into the fallopian tube.

4. Luteal Phase (Days 15–28)

The ruptured follicle transforms into the corpus luteum, producing progesterone to prepare the uterine lining for potential blastocyst implantation.

Understanding Normal Variations vs. When to See a Doctor

In clinical gynecology, a menstrual cycle lasting between 21 and 35 days is classified as physiologically normal. Bleeding duration typically lasts 2 to 7 days. However, consult a healthcare provider if you experience:

Amenorrhea: Absence of periods for 3 consecutive cycles (or 6+ months).
Oligomenorrhea: Infrequent cycles exceeding 35 days.
Menorrhagia: Abnormally heavy or prolonged bleeding (soaking a pad/tampon every hour for consecutive hours).
Severe Dysmenorrhea: Intense pelvic pain or cramping that impairs daily activities.

Clinical Notice & Contraception Warning

Important Medical Disclaimer: This calculator provides statistical projections based on regular cycle lengths. Because stress, travel, illness, hormonal shifts, and polycystic ovary syndrome (PCOS) can unpredictably alter ovulation timing, this tool must NEVER be used as a method of natural birth control, contraception, or clinical diagnosis.

How to Use the Period Calculator

1Select the first day of your last menstrual period (LMP) using the Month, Day, and Year selectors.
2Choose your typical bleeding duration in days (default: 5 days, range: 2 to 10 days).
3Select your average menstrual cycle length (default: 28 days, range: 20 to 45 days).
4Optionally open "+ Settings" to adjust your luteal phase duration or change the forecast span (up to 12 cycles).
5Click "Calculate Period & Cycle Dates" to generate your next period dates, countdown badge, ovulation timing, and multi-cycle schedule.