BabyCalc
Due date, ovulation window, fetal growth percentiles, pregnancy weight gain, and conception date. Trusted math for your journey.
Due Date Calculator
Calculate your estimated due date from your last menstrual period or conception date.
Ovulation Calculator
Estimate your fertile window and ovulation date from your cycle.
Fetal Growth Tracker
See expected fetal size by gestational week — length, weight, and comparisons.
Pregnancy Weight Gain Tracker
Check if your pregnancy weight gain is within recommended ranges by BMI.
Conception Date Calculator
Estimate conception date from due date or last menstrual period.
About BabyCalc
BabyCalc provides free pregnancy and maternal health calculators. Estimate your due date, find your fertile window, track fetal growth, monitor pregnancy weight gain, and calculate conception date.
All tools run in your browser with complete privacy. No data is sent anywhere. Share results via URL with your partner or healthcare provider.
Estimated due date (EDD): the standard calculation (Naegele's rule) adds 280 days to the first day of the last menstrual period, assuming a 28-day cycle with ovulation on day 14. For cycles longer than 28 days, the EDD adjusts later; shorter cycles adjust earlier. IVF due dates use the egg retrieval date: add 266 days for day-0 embryos, 263 days for day-3 transfers, 261 days for blastocyst (day-5) transfers — IVF dating is more precise than LMP dating.
Fertile window and ovulation: ovulation typically occurs 12–16 days before the next expected period. For a 28-day cycle, this is day 14; for a 33-day cycle, it's day 19. Sperm viability (3–5 days) plus egg viability (12–24 hours) creates a fertile window of roughly 5–6 days per cycle centered on ovulation. LH surge testing (OPKs) detects the hormonal trigger 24–36 hours before ovulation — the most actionable predictor for conception timing.
Fetal growth milestones: ultrasound measurements chart growth percentiles against gestational age. Crown-rump length (CRL) is used up to 14 weeks and is accurate to ±5–7 days for dating. After 14 weeks, head circumference (HC), abdominal circumference (AC), and femur length (FL) are combined in formulas (Hadlock) to estimate fetal weight. The 10th–90th percentile range is considered normal growth; deviations trigger additional monitoring.
Pregnancy weight gain guidelines (IOM 2009): normal BMI (18.5–24.9): 25–35 lbs total; overweight (25–29.9): 15–25 lbs; obese (≥30): 11–20 lbs. Minimal gain in the first trimester (1–4 lbs), then approximately 0.5–1 lb per week in the second and third trimesters for normal-weight individuals. Components include baby weight (~7.5 lbs), placenta (~1.5 lbs), amniotic fluid (~2 lbs), blood volume expansion (~4 lbs), and tissue and fat stores.