Dr. BabyPregnancy · Free tools from Dr. Baby
Pregnancy Calculator
Your weeks, your milestones, your next little step.
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The little guide · By Dr. Baby
A pregnancy timeline in one place
This pregnancy calculator turns a last-period date into a simple timeline. It shows estimated gestational age, an estimated due date and the dates when the second and third trimesters begin. You can change the calculation date to see how the timeline looks for a future appointment.
What the timeline measures
Gestational age is counted from the first day of the last menstrual period, before conception usually occurs. The calendar model uses 40 weeks. The second trimester starts at 14 weeks and the third at 28 weeks. The progress bar represents elapsed calendar time, not fetal size, health or readiness for birth.
Turn dates into practical plans
Use the week-by-week guide for a small planning prompt, save names that feel right, or begin your hospital checklist. A timeline is most useful when it makes today easier. If your clinician has assigned a different due date, use that date in the weeks-pregnant calculator instead. Irregular cycles and uncertain dates make period-based estimates less reliable; this tool does not replace clinical dating.
Sources & further reading
A useful place to start
How to use this tool
- Enter the first day of your last period.
- Choose today or another date to calculate the timeline.
- Explore your estimated week, trimester boundaries and linked planning tools.
Questions about pregnancy calculator
Can I use a clinician-confirmed due date?
Use the linked weeks-pregnant calculator and choose Estimated due date. This timeline starts from a last-period date.
Content updated · Methods, sources & limitations