Pregnancy calculators
8 browser-based pregnancy calculators and utilities. Every formula runs locally - no upload, no sign-up, no tracking of the numbers you type.
All pregnancy tools
8 tools, each runs locally in your browser. Click any card to open it.
Baby Formula Calculator takes height, weight, age, sex, activity and returns the matching baby formula result. Runs en…
Ovulation Calculator computes fertile window, ovulation day from last period, cycle length. Runs entirely in your brow…
Period & Ovulation Calculator takes height, weight, age, sex, activity and returns the matching period & ovula…
Pregnancy Conception Date Calculator computes date difference or future/past date from start date, end date, or durati…
Pregnancy Due Date computes estimated due date, current week from last menstrual period date, cycle length. Runs entir…
Pregnancy Trimester Calculator takes height, weight, age, sex, activity and returns the matching pregnancy trimester r…
Pregnancy Weight Gain Calculator takes height, weight, age, sex, activity and returns the matching pregnancy weight ga…
Estimate fetal weight by gestational age using a Hadlock-curve approximation with 10th to 90th percentile reference ra…
About pregnancy
Pregnancy calculators cover the dating, growth, and planning math expecting parents and clinicians use: due date from LMP (Naegele's rule) or ultrasound CRL, gestational age in weeks + days, ovulation and fertile window prediction, fetal growth percentile, baby formula daily intake by weight, baby weight estimation, and contraction timing.
Use these tools for: confirming a due date from a 6-8 week ultrasound, computing gestational age for prenatal visit timing, planning conception with ovulation prediction, monitoring fetal growth against percentile curves, mixing the right formula volume for a 5 kg infant, or timing contractions for labor decision support.
Sources: ACOG (American College of Obstetricians and Gynecologists) dating standards, WHO and CDC fetal growth charts, NICE pregnancy guidelines, FDA infant formula preparation references. All tools are decision support; clinical decisions belong with a licensed OB-GYN or midwife.
Common use cases
Real scenarios where the pregnancy calculators in this category earn their keep.
Due date from LMP
Naegele's rule: LMP + 280 days = EDD. Adjusted for cycle length other than 28 days. The due-date tool runs the math and shows the trimester boundaries.
Ultrasound-confirmed dating
First-trimester CRL (crown-rump length) re-dates the pregnancy when it differs from LMP by more than 5-7 days. The tool flags the discrepancy and recommends the ACOG-preferred date.
Fertile window prediction
5 days before to 1 day after ovulation. Ovulation is typically day 14 of a 28-day cycle. The tool adjusts for shorter or longer cycles.
Fetal growth percentile
Estimated fetal weight (EFW) plotted against gestational age on WHO or Hadlock curves. 10-90th percentile is the normal range; outside flags an investigation.
Infant formula intake
150-200 mL/kg/day for the first 6 months. The formula calculator outputs daily volume and per-feed amounts based on baby weight and feed frequency.
Key terms
Glossary for the formulas and conventions these tools use.
- EDD
- Estimated Due Date. 280 days from LMP (40 weeks). About 5% of births happen on the EDD itself; 80% within 2 weeks before or after.
- LMP
- Last Menstrual Period. First day of last period; the reference date for Naegele's rule.
- Gestational age
- Weeks and days since LMP. 'Pregnant at 12 weeks' means 12 weeks since LMP, not 12 weeks since conception (which is ~2 weeks shorter).
- CRL
- Crown-Rump Length. Embryo or fetus measurement from head to bottom in the first trimester. Most accurate dating method.
- Naegele's rule
- EDD = LMP + 7 days + 9 months. Assumes a 28-day cycle and ovulation on day 14. Adjusted for irregular cycles.
- Trimester
- First: weeks 1-13. Second: weeks 14-27. Third: weeks 28-birth (typically 40).
- Fertile window
- 5 days before ovulation through the day of ovulation. The egg is viable 12-24 hours; sperm 3-5 days.
Frequently asked questions
Short answers to the most common pregnancy questions.