VitaFem Analytics

Women's Health Matrix · A CalculatorFlash calculator

About these tools

For education and personal tracking only. Estimates vary by individual biology and do not replace clinical advice, ultrasound dating, or diagnosis. Discuss results with a qualified clinician.

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FREE EDUCATIONAL TOOLS

Know your cycle.
Trust your timeline.

Three instantly reactive women's health calculators in one dashboard: menstrual cycle and ovulation forecasting, pregnancy due date and milestones by last menstrual period, and adult BMI with pregnancy-aware guidance. For education and personal tracking - not a diagnosis.

Medical disclaimer: Results are estimates based on published population formulas (cycle arithmetic, Naegele's Rule, WHO adult BMI). They are not medical advice and must not delay care. Full disclaimer.

TAB 01 - INPUTS

Cycle Parameters

Updates instantly as you type or slide.

Day 1 is the first day of full flow, not spotting.

28 days
21d28d avg35d45d
21-45
14 days
10d14d typical16d

Time from ovulation to next period. Relatively constant for most people - 14 days if unsure.

How we calculate

Next Period = LMP + cycle length
Ovulation   = Next Period − luteal phase
Fertile     = Ovulation −5d → Ovulation

TODAY'S PHASE

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CYCLE DAY-NEXT PERIOD IN-

NEXT PERIOD

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PEAK FERTILITY

OVULATION DAY

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Highest conception chance

FERTILE WINDOW

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6-day span incl. ovulation

Sperm can survive up to 5 days

Cycle Map - Upcoming Month

Each cell is one day from your last period through next cycle start.

Period Fertile Ovulation Today

PERIOD

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FOLLICULAR

Building to ovulation

LUTEAL

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Next 3 Cycles Forecast

Forecasts assume regular cycles. Stress, illness, travel and conditions like PCOS can shift ovulation. Not for contraception.

GUIDES

How these women's health calculators work

VitaFem Analytics uses well-known population formulas so you can see dates and ranges instantly. Individual biology varies. Treat every output as an estimate and confirm important decisions with a qualified clinician.

Cycle & ovulation

A menstrual cycle is counted from the first day of full flow to the day before the next period. Ovulation is estimated by subtracting luteal-phase length (often about 14 days) from the next period date. The fertile window shown here is the six days ending on ovulation day, because sperm may survive up to about five days and the egg is typically viable for less than a day. Calendar methods cannot confirm ovulation; cervical mucus, LH tests or ultrasound are more specific when timing matters.

Due date (LMP)

Naegele's Rule dates pregnancy from the last menstrual period, not from conception: add seven days, subtract three months and add one year - equivalent to 280 days or 40 weeks for a 28-day cycle. If your average cycle is longer or shorter than 28 days, this tool shifts the estimate by that difference. Only about 5% of births occur on the estimated due date. First-trimester ultrasound is usually preferred for dating when available.

Adult BMI

Body mass index is weight in kilograms divided by height in metres squared. World Health Organization adult groups are underweight below 18.5, normal 18.5-24.9, overweight 25-29.9 and obese at 30 or above. BMI does not separate fat from muscle, does not measure fat location, and should not be used to classify health in pregnancy. Ethnicity-specific and clinical context can change how a result is interpreted.

When to seek care

Use emergency services for severe pelvic or abdominal pain, fainting, very heavy bleeding, pregnancy warning signs (such as severe headache, visual change, chest pain, reduced fetal movement after viability, or fluid leakage), or any symptom that feels urgent. This website cannot triage emergencies.

FAQ

Frequently asked questions

How accurate is an ovulation calculator?

Ovulation calculators estimate the likely fertile window from cycle length and luteal-phase assumptions. For people with regular cycles they are often within a few days, but stress, illness, travel, PCOS, breastfeeding and hormonal contraception can shift ovulation. They are not a fertility diagnosis and are not contraception.

Can I use this ovulation calendar as birth control?

No. Calendar estimates are not a reliable contraceptive method. Sperm can survive several days and ovulation can occur earlier or later than predicted. Use a method recommended by your clinician if you are trying to avoid pregnancy.

How is the pregnancy due date calculated?

This tool uses Naegele's Rule: estimated due date is the first day of the last menstrual period plus 280 days (40 weeks), adjusted if average cycle length is not 28 days. A first-trimester ultrasound is generally more accurate and may change the due date.

What if my cycles are irregular?

Irregular cycles make ovulation and due-date estimates less reliable. Enter your typical average if you have one, and treat results as a rough guide. Discuss irregular bleeding, fertility planning or pregnancy dating with a healthcare professional.

Does VitaFem store my health data?

Calculator inputs are processed in your browser and are not uploaded to a VitaFem server. If you allow advertising cookies, third parties such as Google may set cookies as described in the Privacy Policy. You can reject non-essential cookies.

What is a luteal phase?

The luteal phase is the time from ovulation to the next period. For many people it is close to 14 days and more stable than the first half of the cycle. If you have tracked ovulation, you can adjust the luteal length; otherwise 14 days is a common default.

Why doesn't standard BMI apply during pregnancy?

BMI is weight divided by height squared. In pregnancy, weight includes the baby, placenta, amniotic fluid and increased blood volume, so adult BMI categories are not used to judge health. Clinicians usually compare gestational weight gain with pre-pregnancy BMI instead.

Is this medical advice?

No. VitaFem Analytics provides educational calculators and general information. It does not diagnose, treat or replace care from a physician, midwife or other qualified professional. Seek urgent care for severe pain, heavy bleeding, pregnancy warning signs or any emergency.

Standard published formulas

Naegele's Rule, WHO adult BMI cut-offs and common luteal-phase assumptions, labelled in the interface.

Private by design

Cycle, pregnancy and BMI maths run locally in your browser. We do not require an account to use the tools.

Instantly reactive

Every slider, date and unit toggle recalculates live - no submit button and no page reload.