Pregnancy and Cycle Calculators
These calculators help with planning a pregnancy and following one. Estimate a due date and the current week of pregnancy from the first day of your last period, a known conception date, an IVF transfer or an early ultrasound; find the fertile window and likely ovulation day for the coming cycles; predict upcoming periods from your cycle length; and see the recommended weight gain for each week based on your pre-pregnancy BMI.
4 free tools · no sign-up · no ads
All Pregnancy & Cycle (4)
Pregnancy Due Date Calculator
Due date and current week from last period, conception or IVF transferOvulation Calculator
Fertile window and likely ovulation day for the next cyclesPeriod Calculator
Predict your next periods from cycle and period lengthPregnancy Weight Gain Calculator
Recommended weight gain by week from pre-pregnancy BMI
Which tool do I need?
Work out my due date and how far along I am
Enter the first day of your last period, conception date, IVF transfer or ultrasound date to see the due date, week and trimester.
Find my most fertile days this month
Enter your last period and cycle length to see the fertile window and likely ovulation day for the next few cycles.
Predict when my next periods will start
Enter the start of your last period, cycle length and period length to see the coming dates on a calendar.
Check whether my pregnancy weight gain is on track
Enter your pre-pregnancy height and weight and your current week to compare your gain with the recommended range.
About Pregnancy & Cycle
They use the methods clinicians start from: Naegele's rule with an adjustment for cycle length, a luteal phase of about 14 days, and the Institute of Medicine weight gain ranges. Each tool explains its assumptions and lets you change the ones that vary from person to person, such as cycle length.
Every result is an estimate. Only a small share of babies arrive on the due date, cycles shift with stress, illness and age, and ovulation predictions are not a form of contraception. Your midwife or doctor will refine dates with an ultrasound and can advise on anything that does not look as expected. Dates you enter stay in your browser.
Guides
- How a Due Date Is Calculated, and How Much Weight to GainNaegele's rule, cycle-length and IVF adjustments, when a scan overrides your period date, trimester boundaries, and the IOM 2009 weight gain ranges explained.
- Your Menstrual Cycle in Numbers: Periods, Ovulation and the Fertile WindowHow cycle length is counted, why ovulation sits about 14 days before the next period, where the six-day fertile window comes from, and how far to trust a prediction.
Frequently asked questions
How accurate is a due date calculated from my last period?
It is a good first estimate, but only about 4% of babies are born on their due date. An early ultrasound usually refines it, and most births fall within two weeks either side.
Can I use the ovulation calculator to avoid pregnancy?
No. Ovulation can shift from cycle to cycle and sperm can survive several days, so a calendar estimate is not reliable contraception.
Why does cycle length change the due date?
Naegele's rule assumes ovulation on day 14 of a 28-day cycle. With longer or shorter cycles ovulation happens later or earlier, so the due date moves by the same number of days.
Are the dates I enter in the pregnancy calculators stored?
No. The dates you enter are used only in your browser to calculate the results and are not sent to a server.