What is gestational age vs fetal age?

Gestational age counts from LMP (about 2 weeks before conception). Fetal age is roughly 2 weeks less.

When does each trimester start?

1st: weeks 1–12, 2nd: weeks 13–27, 3rd: week 28 until birth.

Calculate pregnancy weeks and days from your last menstrual period.

Last Menstrual Period

Gestational Age

0 weeks, 0 days

Trimester

1st

Total Days

How to use this calculator

Frequently Asked Questions

How to Use

What it calculates

Shows how many weeks and days pregnant you are from your last menstrual period, plus current trimester.

When to use it

Use for appointment prep, understanding fetal development milestones, or matching ultrasound reports.

Formula

Gestational age = days since LMP; weeks = total days ÷ 7.

Example

LMP 10 weeks ago → 10 weeks 0 days pregnant, second trimester starts at week 13.

Explore More

Find your estimated conception date from due date or last menstrual period.

Estimate your implantation window from ovulation or last menstrual period.

Calculate your estimated due date from embryo transfer day (3-day or 5-day).

Calculate your next period date and cycle info from your last menstrual period.

Calculate your last menstrual period from a known due date.

Estimate fertile and safe days using the calendar method (educational only).