Calculate Your Menstrual Cycle
Menstrual Cycle Phases
| Phase | Days (28-day cycle) | What Happens | Symptoms |
|---|---|---|---|
| Menstruation | Days 1-5 | Uterine lining sheds, bleeding occurs | Cramps, fatigue, mood changes, bloating |
| Follicular Phase | Days 1-13 | Follicles develop, estrogen rises | Energy increases, mood improves |
| Ovulation | Day 14 | Egg released from ovary | Fertile cervical mucus, slight temp rise, cramping |
| Luteal Phase | Days 15-28 | Progesterone rises, uterus prepares | PMS symptoms, breast tenderness, mood swings |
Fertility & Conception Window
| Day Relative to Ovulation | Pregnancy Probability | Notes |
|---|---|---|
| 5 days before | ~10% | Sperm can survive up to 5 days |
| 4 days before | ~16% | Increasing fertility |
| 3 days before | ~14% | Fertile window opens |
| 2 days before | ~27% | High fertility |
| 1 day before | ~31% | Peak fertility |
| Ovulation day | ~33% | Highest pregnancy chance |
| 1 day after | ~10% | Egg viable 12-24 hours |
| 2+ days after | <1% | Fertility window closes |
Understanding Your Menstrual Cycle
What is the Menstrual Cycle?
Definition: The menstrual cycle is the monthly series of changes a woman's body goes through to prepare for pregnancy. It's controlled by hormones (estrogen, progesterone, FSH, LH) and typically lasts 21-35 days, with 28 days being average.
Day 1: First day of menstrual bleeding is considered Day 1 of your cycle. This is when the uterine lining sheds because pregnancy didn't occur. Cycle ends the day before your next period starts.
Normal Variation: Cycle length varies between women and can vary month-to-month for the same woman. Anywhere from 21-35 days is considered normal. Irregularity is common in teens, perimenopause, and due to stress, weight changes, or medical conditions.
The Four Phases in Detail
1. Menstruation (Period) - Days 1-5: Uterine lining breaks down and sheds through the vagina. Bleeding typically lasts 3-7 days. Normal blood loss is 30-40ml (2-3 tablespoons) though it may seem like more. Hormones (estrogen and progesterone) are at lowest levels. Common symptoms include cramps (prostaglandins cause uterine contractions), fatigue, headaches, mood changes, bloating, and back pain. Rest, heat therapy, and over-the-counter pain relievers can help.
2. Follicular Phase - Days 1-13: Overlaps with menstruation but extends beyond. Pituitary gland releases FSH (follicle-stimulating hormone), stimulating ovaries to develop follicles containing eggs. One follicle becomes dominant. Estrogen levels rise as follicle matures, thickening uterine lining. Energy typically increases. Mood often improves. This is the variable phase - cycle irregularity usually occurs here, not in luteal phase.
3. Ovulation - Day 14 (typically): LH (luteinizing hormone) surges, triggering release of mature egg from ovary. Happens about 14 days before next period (not necessarily day 14 of cycle). Egg survives 12-24 hours. Fertile window is 5-6 days (sperm can live up to 5 days). Signs include clear, stretchy cervical mucus (like raw egg white), slight basal body temperature rise (0.5-1°F), mild cramping or twinges (mittelschmerz), and increased libido. Some women feel ovulation; many don't.
4. Luteal Phase - Days 15-28: After ovulation, ruptured follicle becomes corpus luteum, producing progesterone. Progesterone maintains thickened uterine lining for potential pregnancy. If no pregnancy, corpus luteum breaks down around day 24-28, progesterone drops, triggering menstruation. This phase is more consistent (12-16 days, usually 14). PMS symptoms common in late luteal phase including mood swings, irritability, anxiety, breast tenderness, bloating, food cravings, fatigue, and headaches. Symptoms caused by hormone fluctuations and prostaglandins.
Ovulation: The Fertile Window
When It Happens: Ovulation typically occurs 14 days before next period starts. In 28-day cycle, that's day 14. In 30-day cycle, day 16. In 35-day cycle, day 21. Timing varies based on cycle length, not fixed at day 14 for everyone.
Fertile Window: The 6-day period ending on ovulation day. Sperm can survive 5 days in female reproductive tract (waiting for egg). Egg survives 12-24 hours after release. Pregnancy most likely from intercourse 1-2 days before ovulation. Accounts for ~30% of days in cycle when pregnancy is possible.
Signs of Ovulation: Changes in cervical mucus (clear, slippery, stretchy - "egg white" consistency). Basal body temperature rises slightly after ovulation. Ovulation predictor kits (OPKs) detect LH surge 24-36 hours before ovulation. Mild pelvic or abdominal pain (mittelschmerz). Increased sex drive. Breast tenderness. Heightened sense of smell, taste, or vision. Cervix becomes softer, higher, and more open.
Tracking Your Cycle
Why Track: Predict next period for planning activities. Identify fertile days for conception or contraception. Notice irregularities that may indicate health issues. Understand your body's patterns and symptoms. Helpful information for healthcare providers.
Methods: Calendar method (mark first day of each period). Period tracking apps (many free options). Basal body temperature (BBT) charting (take temperature first thing each morning). Cervical mucus monitoring (check daily changes). Ovulation predictor kits (urine tests for LH surge). Fertility monitors (expensive but comprehensive). Symptom journaling (track mood, cramps, energy, etc.).
What to Track: First day of bleeding each month. Last day of bleeding. Cycle length (days from one period start to next period start). Flow intensity (light, medium, heavy). Symptoms (cramps, mood, energy, cravings). Ovulation signs. Sexual activity (if trying to conceive or avoid pregnancy). Any spotting between periods.
Irregular Periods: When to Worry
What's Normal Irregular: First few years after menarche (first period). Perimenopause (years before menopause). After pregnancy or miscarriage. After starting or stopping birth control. Occasional variation (stress, travel, illness, weight change). One missed period without other symptoms usually not concerning.
Concerning Irregularities: Periods consistently shorter than 21 days or longer than 35 days. Missing multiple periods without pregnancy. Extremely heavy bleeding (soaking through pad/tampon every 1-2 hours). Bleeding lasting longer than 7 days. Severe pain interfering with daily activities. Bleeding between periods regularly. Periods after menopause (no period for 12 months). Sudden changes in established pattern.
Potential Causes: PCOS (polycystic ovary syndrome), thyroid disorders (hypo/hyperthyroidism), endometriosis, uterine fibroids or polyps, premature ovarian failure, pituitary disorders, eating disorders or extreme weight loss, excessive exercise, stress, certain medications, and reproductive cancers (rare).
Period Pain Management
Over-the-Counter Options: NSAIDs (ibuprofen, naproxen) - most effective, start before cramps begin if possible. Acetaminophen for pain relief. Take with food to prevent stomach upset. Follow dosage instructions carefully.
Heat Therapy: Heating pad or hot water bottle on lower abdomen or back. Warm bath or shower. Heat patch designed for cramps. Works by relaxing uterine muscles and increasing blood flow.
Lifestyle Approaches: Regular exercise (especially aerobic) reduces cramps. Adequate sleep. Stress management (yoga, meditation, breathing exercises). Magnesium supplements (consult doctor first). Omega-3 fatty acids. Avoiding caffeine, alcohol, and smoking. Light stretching or yoga poses (child's pose, cat-cow).
When to See Doctor: Pain interferes with daily activities or work. Over-the-counter medications don't help. Pain worsens over time. Heavy bleeding (soaking through products every 1-2 hours). Severe pain during sex. Painful bowel movements during period. Doctor can investigate underlying causes and prescribe stronger treatments.
Frequently Asked Questions
How accurate is the period calculator?
For women with regular cycles, predictions are reasonably accurate (within 1-2 days). However, many factors can affect timing: stress, illness, travel, weight changes, exercise, medications. The calculator assumes regular ovulation 14 days before next period. Women with irregular cycles will have less accurate predictions. Tracking over 3-6 months improves accuracy as you learn your personal pattern.
Can I get pregnant on my period?
Unlikely but possible, especially with short cycles or long periods. Sperm can survive up to 5 days. If you have 24-day cycle and 7-day period, ovulation might occur on day 10, just 3 days after period ends. Sperm from intercourse on day 5 (during period) could still be alive. For most women with 28-day cycles, pregnancy during period is very rare. Don't rely on this for contraception.
When am I most fertile?
Most fertile 1-2 days before ovulation and ovulation day itself. Fertile window spans 5-6 days total (5 days before and day of ovulation). For 28-day cycle, that's typically days 9-14, with peak fertility days 12-14. Egg survives 12-24 hours, but sperm can wait up to 5 days for egg to be released.
Why is my cycle irregular?
Many reasons: Stress (physical or emotional), weight changes (gain or loss), excessive exercise, poor sleep, thyroid problems, PCOS (polycystic ovary syndrome), perimenopause, after pregnancy or miscarriage, starting/stopping birth control, eating disorders, chronic illness, certain medications. Occasional irregularity is normal. Consistently irregular cycles warrant doctor visit to rule out underlying conditions.
Can I track ovulation without tests?
Yes, through cervical mucus monitoring (most reliable natural method) and basal body temperature (BBT) charting. Cervical mucus becomes clear, slippery, and stretchy around ovulation (like raw egg white). BBT rises 0.5-1°F after ovulation. Some women feel ovulation pain (mittelschmerz). Combine methods for better accuracy. Takes 2-3 months to learn your patterns.
How long does a normal period last?
Typically 3-7 days, with 5 days being average. Less than 2 days or more than 7 days may indicate hormonal imbalance or other issues. Flow usually heaviest first 2 days, then tapers off. Normal blood loss is 30-80ml (2-5 tablespoons) total per period. If soaking through pad/tampon every 1-2 hours, flow is too heavy - see doctor.
What if I miss a period?
First, take pregnancy test if sexually active. Other causes: stress, weight loss, excessive exercise, illness, travel, PCOS, thyroid problems, perimenopause, recent birth control changes, certain medications. One missed period occasionally is usually not concerning. Missing multiple periods (3+) without pregnancy requires doctor visit. Amenorrhea (absent periods) can indicate hormonal imbalance or other health issues.
Can I speed up or delay my period?
Hormonal birth control can regulate and control timing. Combined oral contraceptives allow skipping placebo week to delay period. Some methods stop periods entirely (Depo-Provera, some IUDs, continuous pill use). Natural methods (vitamin C, parsley, etc.) lack scientific evidence. Don't try to force period - can be harmful. If trying to delay for special event, discuss with doctor at least 2-3 months ahead for birth control prescription.
Common Period Myths Debunked
- Myth: Cycles should be exactly 28 days. Reality: 21-35 days is normal. Your cycle length is unique to you.
- Myth: You can't get pregnant during period. Reality: Unlikely but possible with short cycles or long periods.
- Myth: Ovulation always happens day 14. Reality: Occurs ~14 days BEFORE next period, not day 14 of cycle.
- Myth: Exercise makes cramps worse. Reality: Regular exercise actually reduces cramps and PMS symptoms.
- Myth: You lose lots of blood. Reality: Average is 30-40ml (2-3 tablespoons), though it seems like more.
- Myth: Tampons can get lost inside. Reality: Cervix prevents tampons from going past vagina. Can't get lost.
- Myth: Sync up with other women. Reality: No scientific evidence. Seeming sync is coincidence.
- Myth: Can't swim during period. Reality: Safe to swim. Tampons or menstrual cups work in water.
- Myth: PMS isn't real. Reality: 90% of women experience some PMS symptoms due to hormone changes.
Period Essentials & Products
Menstrual Products
Pads/Sanitary Napkins: External, adhere to underwear. Various absorbencies (light, regular, heavy, overnight). Change every 4-8 hours. Good for light days, overnight, first period. Can feel bulky, may shift.
Tampons: Internal, inserted in vagina. Various absorbencies. Change every 4-8 hours, never exceed 8 hours (TSS risk). Good for swimming, sports. Learning curve to insert. Use lowest absorbency needed.
Menstrual Cups: Reusable silicone cup inserted in vagina. Can wear up to 12 hours. Eco-friendly, cost-effective long-term. Steeper learning curve. Requires cleaning between uses. Lasts years with proper care.
Period Underwear: Absorbent underwear replaces or backs up other products. Reusable, washable. Good for light days, backup protection, overnight. Initial cost higher but reusable.
Reusable Pads: Cloth pads that snap to underwear. Washable and reusable. Eco-friendly. Requires washing/carrying system when out.
When to See a Doctor
- Periods lasting longer than 7 days regularly
- Bleeding so heavy you soak through pad/tampon every 1-2 hours
- Severe pain not relieved by over-the-counter medication
- Missed periods (not pregnant) for 3+ months
- Bleeding between periods regularly
- Sudden changes in cycle pattern
- Cycles shorter than 21 days or longer than 35 days consistently
- Period symptoms interfering with daily life, work, or school
- Fever, unusual discharge, or foul odor (possible infection)