Next Period Calculator

To predict your next period: Take the first day of your last period and add your average cycle length. For example, if your last period started January 1st and your cycle is 28 days, your next period should start around January 29th. Our calculator automates this and shows you a full calendar of upcoming periods for months ahead.

A normal menstrual cycle ranges from 21 to 35 days, with 28 days being the oft-cited 'average.' However, many healthy women have cycles outside this range. What matters most is YOUR pattern—if you're consistently 32 days, that's normal for you. Cycles shorter than 21 days or longer than 35 days may warrant a doctor's visit, especially if they're new for you.

Common reasons for a late period include: (1) PREGNANCY—if sexually active, this is the most common cause. (2) STRESS—emotional or physical stress affects hormone production. (3) WEIGHT CHANGES—significant gain or loss impacts estrogen. (4) INTENSE EXERCISE—overtraining can delay ovulation. (5) HORMONAL CONDITIONS—PCOS, thyroid disorders. (6) MEDICATIONS—some drugs affect cycles. (7) PERIMENOPAUSE—cycles become irregular before menopause. If over 7 days late, consider a pregnancy test; if frequently irregular, consult a doctor.

PMS (Premenstrual Syndrome) refers to physical and emotional symptoms that occur 1-2 weeks before your period. Common symptoms include mood swings, irritability, bloating, breast tenderness, food cravings, fatigue, headaches, and cramping. Symptoms are caused by hormone fluctuations (progesterone and estrogen) and typically improve once your period starts. Our calculator shows your 'PMS Zone' so you can prepare.

Accuracy depends on your cycle regularity. For regular cycles (consistent length month-to-month), predictions can be accurate within 1-2 days. For irregular cycles (varying by 7+ days), predictions are less reliable. Factors that can throw off predictions include stress, travel, illness, weight changes, and hormonal shifts. Track multiple cycles to establish your average and improve prediction accuracy.

The menstrual cycle has several phases: (1) MENSTRUAL (Day 1-5): Uterine lining sheds, bleeding occurs. (2) FOLLICULAR (Day 1-13): Hormones stimulate follicle development, estrogen rises. (3) OVULATION (~Day 14): Egg is released, peak fertility. (4) LUTEAL (Day 15-28): Progesterone rises, uterus prepares for implantation. (5) PMS ZONE (Day 21-28): Hormone drop causes premenstrual symptoms. Our calculator shows which phase you're currently in.

If you're sexually active and your period is late, you can take a home pregnancy test on the first day of your missed period. For the most accurate results, wait until you're at least 7 days late—this allows hCG (pregnancy hormone) to build up for detection. Test with first morning urine for highest concentration. If negative but still no period after another week, retest or see a doctor.

A normal period lasts 3-7 days, with the average being 5 days. The first 1-2 days are typically the heaviest, then flow gradually lightens. Periods shorter than 2 days or longer than 7 days may indicate hormonal imbalances. If your period length changes significantly from your norm, or you experience very heavy bleeding (soaking through a pad/tampon hourly), consult a healthcare provider.

Yes, stress is one of the most common causes of delayed or missed periods. Stress hormones (cortisol, adrenaline) interfere with the hypothalamus, which controls the pituitary gland and reproductive hormones. This can delay or suppress ovulation, which in turn delays your period. The delay can range from a few days to missing a period entirely. Managing stress through exercise, sleep, and relaxation techniques can help regulate your cycle.

Cycle tracking means recording your period start dates, lengths, and symptoms over time. Benefits include: (1) Predicting your next period more accurately. (2) Planning events around your cycle. (3) Identifying irregularities early. (4) Understanding your PMS patterns. (5) Providing useful data for fertility planning or doctor visits. (6) Recognizing what's 'normal' for YOUR body. Our calculator helps automate part of this process.

See a healthcare provider if: (1) Your period is more than 7 days late (after ruling out pregnancy). (2) You miss 3+ periods in a row. (3) Periods are suddenly much heavier, lighter, or more painful than usual. (4) Cycles are consistently shorter than 21 days or longer than 35 days. (5) You experience bleeding between periods. (6) Periods last more than 7 days. (7) PMS symptoms severely impact your life. These could indicate conditions like PCOS, thyroid disorders, or endometriosis.

Age significantly impacts cycles: TEENS: Cycles are often irregular for the first 1-2 years after menarche as hormones stabilize. 20s-30s: Cycles typically become more regular and predictable. 40s: Perimenopause begins, cycles may become irregular, shorter, longer, or skipped. 50s+: Menopause (no period for 12 months). What's 'normal' changes with life stage. Keep tracking to understand your evolving pattern.

NO. This calculator should NOT be used for contraception. It only predicts when your period will start—not your fertile days—and even fertility awareness methods have high failure rates (15-25% typical use). Cycles can shift unpredictably, and calendar-based methods don't account for that. If you want to avoid pregnancy, use proven contraceptive methods and consult a healthcare provider.

To manage PMS: (1) EXERCISE regularly—releases endorphins and reduces cramps/mood issues. (2) EAT WELL—reduce salt (bloating), caffeine (irritability), and sugar. (3) SLEEP—aim for 7-9 hours to help mood. (4) HYDRATE—helps with bloating and headaches. (5) TAKE PAIN RELIEVERS—ibuprofen or naproxen for cramps. (6) USE HEAT—heating pad for cramps. (7) SUPPLEMENTS—calcium, magnesium, B6 may help some women. Severe PMS (PMDD) may require medical treatment.

No. This calculator runs entirely in your browser. Your period dates and cycle information are processed locally on your device and are never sent to our servers or stored anywhere. When you close or refresh the page, all data is cleared. We believe menstrual health data is deeply personal and have designed this tool with privacy as the priority.