Free · Private · Evidence-based

Pregnancy & Fertility Calculator — Know your dates, trust your journey

Twelve gentle, precise calculators for every step — from finding your fertile days to counting down the weeks until you meet your baby. No sign-up, nothing stored, just answers. Every calculation runs entirely in your browser, with clear educational guides reviewed against trusted medical sources.

Pregnancy calculators

• Due Date Calculator — estimate your due date from your last period, conception date or IVF transfer.
• Pregnancy Week Calculator — find your exact week and day of pregnancy, plus your current trimester.
• Conception Date Calculator — work backwards from your due date to your likely conception date.
• IVF Due Date Calculator — precise due dates for 3-day, 5-day and 6-day embryo transfers.
• Trimester Calculator — see which trimester you are in and exactly when each one starts and ends.
• Pregnancy Milestone Calculator — key appointments, scans and milestones dated to your pregnancy.
• Baby Size & Weight Tracker — week-by-week size comparisons, length and estimated weight.
• Pregnancy Weight Gain Calculator — recommended gain ranges based on your pre-pregnancy BMI (IOM).

Ovulation & fertility calculators

• Ovulation Calculator — pinpoint your ovulation date, fertile window and next period.
• Fertile Window Calculator — see your fertile days and your two peak-fertility days at a glance.
• Pregnancy Test Calculator — learn the earliest and most accurate days to take a home test.
• Period & Cycle Calculator — forecast your next periods, ovulation and fertile days.

From the blog

• 10 Early Signs of Pregnancy to Watch For — the earliest clues your body may give you, and when a test gives a reliable answer.
• How to Track Ovulation: 5 Methods That Actually Work — calendar math, basal temperature, cervical mucus, OPKs and physical signs.
• How Your Due Date Is Calculated: Naegele's Rule Explained — the math behind your due date and why only 1 in 20 babies arrives on the exact day.
• IVF Due Dates: Why They're the Most Accurate of All — how IVF due dates are calculated for fresh, frozen and donor cycles.
• How Much Weight Should You Gain During Pregnancy? — IOM guidelines based on your pre-pregnancy BMI.
• Baby Size Week by Week: From Poppy Seed to Pumpkin — what is really developing each trimester.
• The Three Trimesters: What Changes and Why It Matters — what defines each trimester and the key appointments.
• Understanding Your Fertile Window: The 6 Days That Matter — why the window is six days and which days give the highest chance.
• Irregular Periods and Fertility: What You Need to Know — what irregular cycles can signal and when to see a specialist.
• The First Trimester: What to Expect Week by Week — weeks 1 to 13, the most dramatic development of pregnancy.

Guides & resources

• Pregnancy Guide — week-by-week development, fertility basics and what to expect at every key appointment.
• Blog — original articles on due dates, ovulation, IVF, weight gain, baby size and more.
• About Us — who we are and why we built these tools.
• Contact — get in touch with questions or feedback.

Questions, answered

How accurate is a due date calculator?

A due date calculated from your last menstrual period is a well-established estimate, but only about 4–5% of babies arrive on their exact due date. Most arrive within a window of about two weeks before or after. An early ultrasound can refine the estimate further.

Which calculator should I start with?

If you are pregnant, start with the Due Date Calculator, then use the Pregnancy Week Calculator to follow your progress. If you are trying to conceive, begin with the Ovulation Calculator or Fertile Window Calculator to time intercourse.

How is my due date calculated?

The standard method (Naegele's rule) adds 280 days — 40 weeks — to the first day of your last period, adjusted for your cycle length. From a known conception date we add 266 days, and IVF due dates are calculated from the embryo transfer date and embryo age.

Can I use these tools with irregular cycles?

Yes, but treat the results as rougher estimates. Cycle-based calculations assume ovulation 14 days before your next period, which varies more with irregular cycles. An ovulation predictor kit or early ultrasound gives more reliable timing.

Is my data stored or shared?

No. Every calculation runs entirely in your browser. We never see, store or share the dates you enter, and there is nothing to sign up for.

Are these calculators a substitute for medical advice?

No. They provide evidence-based estimates for informational purposes only. Always confirm your dates and discuss any concerns with your doctor or midwife.

All results are estimates for informational purposes only and are not a substitute for professional medical advice, diagnosis or treatment. Please enable JavaScript to use the interactive calculators.