Pregnancy Calculators
Conception Calculator
Estimate your conception date from a last period date, a due date, or a birth date, with the specific formula behind each of the three methods.
Due Date Calculator
Estimate your due date using Naegele's rule with a cycle-length adjustment, plus your current gestational age and trimester from your last period.
Due Date Calculator
Estimate your due date from a last period date, a conception date, or an IVF embryo transfer date, using the formula matched to each starting point.
Fetal Weight Calculator
Estimate fetal weight from BPD, HC, AC and FL ultrasound measurements using the 4-parameter Hadlock formula, the obstetric ultrasound standard.
IVF Due Date Calculator
Estimate your IVF due date from your embryo transfer date and transfer type, with the fertilization date and equivalent LMP date both shown.
Ovulation Calculator
Calculate your estimated ovulation day and five-day fertile window from your last period date, average cycle length, and luteal phase length.
Ovulation Calculator
Estimate ovulation day either forward from your last period and cycle length, or backward from your next expected period and luteal phase length.
Pregnancy Conception Calculator
Estimate both your likely conception window and your projected due date together from a single last period date and average cycle length.
Pregnancy Week Calculator
Find your current pregnancy week, day, and trimester from either your last menstrual period date or a known clinician-provided due date result.
Pregnancy Weight Calculator
Find your pre-pregnancy BMI category and the IOM-recommended total pregnancy weight gain range in pounds and kilograms that applies to it.
Pregnancy Weight Gain Calculator
Track your pregnancy weight gain against an IOM-based target range paced week by week for your pre-pregnancy BMI category and current week.
Tracking a Pregnancy Week by Week, With Real Numbers
Pregnancy milestones are almost always expressed as estimates and ranges rather than fixed dates — a due date is a statistical estimate, ovulation timing shifts cycle to cycle, and healthy weight gain ranges depend on starting BMI. These calculators apply the same standard clinical formulas used to estimate due dates, track conception timing, and monitor healthy progression through pregnancy.
Popular Pregnancy Calculators
Eleven tools span dating, conception, and tracking:
- Due Date Calculator — estimates delivery date from last menstrual period or conception date using standard gestational dating.
- Ovulation Calculator — estimates the fertile window based on cycle length and typical ovulation timing.
- IVF Due Date Calculator — calculates due date based on embryo transfer date, which follows a different dating method than natural conception.
- Pregnancy Weight Gain Calculator — tracks recommended weight gain range based on pre-pregnancy BMI.
- Fetal Weight Calculator — estimates fetal weight at a given gestational age based on standard growth curves.
Why Due Dates Are Estimates, Not Predictions
The standard due date calculation (Naegele's rule, adding 280 days to the last menstrual period) assumes a textbook 28-day cycle with ovulation on day 14, which doesn't match every person's actual cycle — this is exactly why only a small percentage of babies are born on their exact calculated due date, with most arriving within a normal range of a week or two either side. IVF pregnancies use a more precise dating method based on the known embryo transfer date rather than an estimated ovulation date, which is why IVF due date calculations tend to be somewhat more accurate than standard LMP-based estimates.
Frequently Asked Questions
Why does recommended pregnancy weight gain depend on starting BMI?
Clinical guidelines set different healthy weight gain ranges for underweight, normal weight, overweight, and obese starting BMI categories, since the same total weight gain carries different risk profiles depending on starting body composition.
Is a fetal weight estimate from a calculator as accurate as an ultrasound measurement?
No — ultrasound-based estimates use actual measured fetal dimensions, while a general calculator estimate uses population averages for gestational age, so an ultrasound from a healthcare provider is more accurate for an individual pregnancy.
Explore More
Planning for after the baby arrives? See the Baby & Parenting Calculators, or check nutrition needs during pregnancy in the Nutrition Calculators.