Pregnancy Calculators
Due dates, weeks, and ovulation. Every result is an estimate for planning. An ultrasound or a clinician’s dating replaces these numbers when they disagree.
Due date
Use the period calculator when you know the first day of bleeding. Use the ovulation calculator when you know ovulation or conception. They answer the same kind of question from different starting points, so they are separate pages.
How far along
Week count starts at the last period. Pregnancy months on the chart are unequal groups of weeks, not calendar months.
Fertility
Ovulation timing is a different question from the due date. The fertile window here is an estimate from cycle length.
Guides
- How a pregnancy due date is calculated
280 days from the last period, with cycle-length examples.
- Due date from ovulation or conception
266 days from either date, and why they share one rule.
- How many weeks pregnant am I?
Days since the last period, divided by 7.
- Pregnancy weeks to months chart
Unequal months from week 1 through week 40.
- Pregnancy trimester dates
Week 13 and week 28, with a worked calendar.
- How many days is a pregnancy?
280 days from the period, 266 days from conception.
- How accurate are pregnancy due dates?
Why the date is a window, and what replaces it.
- Ovulation date vs conception date
Egg release, fertilization, and why implantation is a later step.