Pregnancy Tools
Simple calculators for dating a pregnancy — estimated due date, gestational age, and trimester.
About These Tools
Pregnancy dates are usually estimated from the first day of your last menstrual period. That convention assumes a 28-day cycle with ovulation on day 14, which is not true for everyone, so both calculators here let you work from a conception or transfer date instead when you know it. Estimates from an early ultrasound are generally more accurate still, and may revise the date your provider records.
Everything runs in your browser. Nothing you enter is sent to a server or stored, which matters more than usual for this kind of information.
Important Note
These tools provide estimates for educational purposes only. They are not medical advice. Always consult your healthcare provider for pregnancy care.
Frequently Asked Questions
How accurate is a due date estimate?
Only a small proportion of babies are born on their estimated due date, and most arrive within two weeks either side. A due date describes a window rather than a specific day.
Why is pregnancy counted from my last period?
Because that date is usually known while the exact date of conception often is not. As a result, gestational age runs about two weeks ahead of fetal age.
Should I use my last period or an ultrasound date?
An early ultrasound is generally more accurate for establishing gestational age. If your provider records a different date, that date takes precedence over any calculator estimate.