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Gestational Week & Day Estimator

Pregnancy Week Calculator

Quickly understand how many weeks and days pregnant you are, what trimester you are in, and calculate your gestational age for any future date.

How Many Weeks Pregnant Am I?

Enter the first day of your last period to calculate your current gestational week, completed days, trimester, and projected week on any future date.

Standard obstetrical dating counts from the first day of bleeding of your last menstrual cycle.
Current Gestational Status
10 Weeks, 0 Days
You are currently in Week 11 of pregnancy
Completed Weeks
10 w
70 total days
Current Trimester
First Trimester
Weeks 1–13
Estimated Due Date
April 28, 2027
40 weeks milestone
Estimated Conception
August 5, 2026
Approx. 14 days after LMP

How far along will I be on another date?

Select an upcoming date (e.g. an appointment, travel date, or celebration) to see your projected gestational age.

On November 29, 2026:
You will be approximately 18 weeks and 4 days pregnant (Week 19, Second Trimester).
🍑View Week 10 Baby Size (Apricot) →📖Read Week 10 Development Guide →🧭Calculate Trimester Schedule →

How Are Pregnancy Weeks Counted?

In clinical obstetrics, pregnancy is measured in completed weeks plus additional days. For example, if your calculator result reads 14 weeks, 3 days:

  • You have finished 14 full weeks of gestation.
  • You are currently 3 days into your 15th week of pregnancy.
  • You have officially entered the Second Trimester (which begins at 14 weeks, 0 days).

Explore Related Pregnancy Tools

The Science of Dating

How Pregnancy Weeks Are Calculated

Understanding the difference between gestational age and conception age brings clarity to your timeline.

01

Naegele's Rule (280 Days)

Clinically, pregnancy is measured from the first day of your last menstrual period (LMP), not the date of conception. A standard gestation spans 40 weeks, which equals 280 calendar days.

02

Gestational vs. Conception Age

Because ovulation typically happens about 14 days after your period starts, your baby is conceived about 2 weeks into your counted gestational age. When you are 4 weeks pregnant, your baby has been growing for approximately 2 weeks.

03

Trimester Boundaries

According to ACOG standards, Trimester 1 covers weeks 1–13. Trimester 2 covers weeks 14–27. Trimester 3 starts at week 28 and continues until delivery.

Common Questions

Pregnancy Calculation FAQ

Reliable, evidence-based answers to frequently asked questions about gestational dating and timelines.

How is a pregnancy due date calculated?
Medical providers calculate estimated due dates using Naegele's rule: by adding 280 days (40 weeks) to the first day of your last normal menstrual period (LMP). If your menstrual cycle is regularly longer or shorter than the standard 28-day model, the calculation can be adjusted accordingly.
How many weeks is a full-term pregnancy?
A full-term pregnancy is generally considered 40 weeks (280 days) from your LMP. Medical guidelines classify babies born between 37 weeks and 38 weeks and 6 days as 'early term', between 39 weeks and 40 weeks and 6 days as 'full term', and 41 weeks to 41 weeks and 6 days as 'late term'.
How are pregnancy weeks counted?
Pregnancy weeks describe completed weeks plus extra days. For example, if you are at '12 weeks, 3 days', you have completed 12 full weeks and are currently experiencing your 13th week of pregnancy.
What is the difference between gestational age and conception age?
Gestational age is measured from the first day of your last period, before ovulation and fertilization actually occur. Conception age (fetal age) begins at the moment the egg is fertilized, which typically takes place approximately 14 days after your period. Gestational age is standard in medical obstetrics.
Can my healthcare provider give me a different due date?
Yes, and this is completely normal. An early first-trimester ultrasound dating scan (crown-rump length measurement) provides the most precise estimate of fetal development. If there is a notable discrepancy between your LMP date and the ultrasound measurement, your clinician will update your official estimated due date.
How accurate is an estimated due date?
Only about 4% to 5% of babies arrive precisely on their estimated due date. It is best considered an estimated arrival window; roughly 80% of healthy infants are born within a two-week window before or after the estimated date.