Pregnancy Calculator by Weeks — Due Date Online
Calculate your pregnancy week and estimated due date (EDD) from your last menstrual period or conception date. With progress bar and weekly milestones. No signup.
The date your last period started
Usually 28 days (range 21–35)
How to use the calculator
Three simple steps to find your pregnancy week, due date and what is happening this week.
Pick a mode
By the first day of your last period, or by conception date if you know it precisely.
Enter the date
Provide the date and (for LMP mode) your cycle length so the ovulation correction is accurate.
Get the result
You will see the current week, due date, trimester and milestones for your stage of pregnancy.
Calculator features
Two calculation modes
By last menstrual period (LMP) with cycle-length adjustment, or directly by known conception date.
Weekly milestones
For each key week — a short description of what is happening with the baby and which exams are due.
Maternity leave dates
The calculator automatically estimates maternity-leave start and end (from week 30, 140 days long).
Frequently asked questions about pregnancy weeks
How is gestational age calculated?
Doctors use the gestational age, counted from the first day of the last menstrual period (LMP), not from conception. This is convenient because most women remember their period date, but few know the exact conception date. Gestational age is about 2 weeks more than the actual embryo age, because ovulation and conception typically happen in the middle of the cycle.
What is the EDD and how is it computed?
EDD stands for Estimated Due Date. By Naegele's rule: EDD = first day of last period + 280 days (40 gestational weeks). If your cycle is longer or shorter than 28 days, the calculator shifts the EDD accordingly — for a 32-day cycle, the EDD moves 4 days later. In conception mode, EDD = conception date + 266 days (38 weeks).
When does maternity leave start?
In Russia, statutory maternity leave starts at gestational week 30 and lasts 140 days — 70 days before and 70 days after birth. For multiple pregnancy it starts earlier, at week 28, and lasts 194 days (84 before + 110 after). Other countries have different rules; check your local regulations for exact entitlements.
How accurate is the calculator?
An LMP-based estimate is approximate, with typical accuracy of about ±5 days. It assumes ovulation in the middle of the cycle, but real ovulation may happen earlier or later. The most accurate way to date a pregnancy is a first-trimester ultrasound (especially weeks 8–12). This calculator is for informational use only and does not replace a consultation with a qualified doctor or medical examination.