Pregnancy Calculator
Estimate how many weeks pregnant you are, your due date, trimester, key pregnancy dates and a week-by-week fetal size reference from LMP, conception, IVF or ultrasound dating.
Pregnancy details
How pregnancy weeks are estimated
English search results for pregnancy calculators expect a practical answer to two questions: how many weeks pregnant am I, and what is my estimated due date. Medical dating usually counts gestational age from the first day of the last menstrual period.
Gestational age in completed weeks from the first day of the last menstrual period.
Classic 40-week due date estimate for a 28-day cycle.
Which input should you use
| Input | Best use | Main limitation |
|---|---|---|
| Last menstrual period | Known LMP with a reasonably regular cycle | Late ovulation or irregular cycles can shift dating |
| Conception or ovulation | Confirmed ovulation or fertility-treatment timing | Intercourse date is not always conception date |
| IVF transfer | Known transfer date and embryo age | Use the embryo age from the clinic record |
| Ultrasound dating | A report already states gestational age | The calculator does not interpret fetal measurements |
Frequently Asked Questions
Sources and References
- Methods for Estimating the Due DateACOG
- Definition of Term PregnancyACOG/SMFM
- When Pregnancy Goes Past Your Due DateACOG
- Length of human pregnancy and contributors to its natural variationHuman Reproduction
- Pregnancy week by weekMarch of Dimes
Calculations are based on the listed reference sources. Links open in a new tab.
Related Tools
Estimate a pregnancy due date from last menstrual period, conception date, IVF transfer or ultrasound dating, with term windows and reverse planning.
Estimate a likely conception date and fertile window from a birth date, due date, last menstrual period or confirmed ovulation date.