Pregnancy Calculators
Calculate baby age, baby weight gain and conception and other pregnancy calculations.
All Pregnancy Calculators
Pregnancy Guides
How a Pregnancy Due Date and Current Week Are Calculated
A pregnancy due date is simply the first day of the last menstrual period plus 280 days — and the current week and trimester follow from counting how many days have passed since that same starting date.
Read guideHow an Ovulation Date and Fertile Window Are Calculated
Ovulation is estimated by counting backward 14 days from the next expected period, since the post-ovulation luteal phase is a relatively fixed length — and a longer overall cycle shifts that ovulation date later, not the 14-day countdown itself.
Read guideHow Conception Date Is Estimated (And How It Differs from the Due Date Calculation)
Conception date is estimated as roughly 14 days after the start of your last menstrual period (LMP), with a several-day fertile window around that point, since ovulation — not the period itself — is what actually determines when conception can occur.
Read guideHow Your Pregnancy Due Date Is Calculated (Naegele's Rule Explained)
The standard due-date estimate is simply the first day of your last menstrual period (LMP) plus 280 days (40 weeks) — a method called Naegele's rule — which counts from before conception actually happens, not from conception itself, which is why "40 weeks pregnant" doesn't mean 40 weeks since conception.
Read guideHow Much Weight Should You Gain During Pregnancy? IOM Guidelines Explained
Recommended total pregnancy weight gain depends on your pre-pregnancy BMI category, not a single fixed number for everyone — someone starting underweight is guided toward gaining more than someone starting overweight, since the goal is a healthy total weight range for the pregnancy, not the same absolute gain regardless of starting point.
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