Gestational Age Calculator
Calculate your pregnancy due date and current gestational age based on your last menstrual period or conception date. Track your pregnancy progress and know when to expect your baby.
Time until the baby is born
Pregnancy Timeline
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1-12 | Organ formation, heartbeat begins |
| Second | 13-27 | Rapid growth, movement felt |
| Third | 28-40 | Final development, weight gain |
About Gestational Age Calculator
Gestational age is the common term used during pregnancy to describe how far along the pregnancy is. It is measured in weeks from the first day of the woman's last menstrual period (LMP) to the current date. This calculator helps you determine your current gestational age and estimated due date.
How Gestational Age is Calculated
Gestational age is calculated from the first day of your last menstrual period (LMP), not from the date of conception. Pregnancy typically lasts about 40 weeks from the first day of your last period. This is called the gestational age and is about two weeks ahead of when conception actually occurs.
Calculation Methods:
- Naegele's Rule: Add 7 days to the first day of your LMP, then subtract 3 months. This gives an estimated due date (EDD).
- Ultrasound Measurement: Early ultrasound measurements (especially first trimester) can provide a more accurate estimate of gestational age.
- Conception Date: If you know your conception date, add 266 days (38 weeks) to estimate your due date.
Pregnancy Trimesters
Pregnancy is divided into three trimesters:
- First Trimester (Week 1 to Week 12): The baby develops its organs and structures. Major organs begin to form, and the heartbeat starts.
- Second Trimester (Week 13 to Week 27): The baby grows rapidly. You may start to feel the baby move, and the sex can often be determined.
- Third Trimester (Week 28 to Week 40): The baby gains weight and prepares for birth. The lungs mature, and the baby moves into position for delivery.
Important Milestones
Here are some key milestones in fetal development:
- Week 4: Neural tube forms (brain and spinal cord)
- Week 8: All major organs have begun to form
- Week 12: Risk of miscarriage decreases significantly
- Week 20: Baby's movements can be felt (quickening)
- Week 24: Baby has a chance of survival if born prematurely
- Week 37: Considered full-term