Baby Gestational Age Calculator
'/%3E%3Ccircle cx='48' cy='39' r='19' fill='%23f2c9a5'/%3E%3Cpath d='M27 35c3-16 39-17 42 2-8-8-27-9-42-2z' fill='%23374151'/%3E%3Cpath d='M21 86c5-24 49-28 56 0z' fill='%232563eb'/%3E%3Ccircle cx='41' cy='41' r='2' fill='%23111827'/%3E%3Ccircle cx='55' cy='41' r='2' fill='%23111827'/%3E%3Cpath d='M42 52c4 3 9 3 13 0' stroke='%2392400e' stroke-width='3' fill='none' stroke-linecap='round'/%3E%3C/svg%3E)
Reviewed by Calculator Editorial Team
Track your baby's gestational age with our free online calculator. Whether you're monitoring your pregnancy or planning for a baby, this tool helps you understand your baby's development stage based on your last menstrual period (LMP) or ultrasound date.
How to Use This Calculator
Using our baby gestational age calculator is simple:
- Enter your last menstrual period (LMP) date or the date of your first prenatal ultrasound.
- Select whether you're using the LMP method or ultrasound method.
- Click "Calculate" to see your baby's gestational age.
- Review the development stage information to understand what your baby is capable of at this age.
The calculator provides your baby's age in weeks and days, along with a visual representation of the pregnancy timeline.
Gestational Age Formula
The standard pregnancy duration is 40 weeks (280 days). The gestational age is calculated based on either:
LMP Method
Gestational age (weeks) = (Current date - LMP date) / 7
Gestational age (days) = (Current date - LMP date) % 7
Ultrasound Method
Gestational age (weeks) = Ultrasound date + (Ultrasound measurement in weeks)
Gestational age (days) = (Current date - Ultrasound date) % 7
The calculator uses these formulas to provide an accurate estimate of your baby's gestational age.
Interpreting Your Results
Your baby's gestational age helps you understand their development stage. Here's what to expect:
| Weeks | Development Stage | Key Milestones |
|---|---|---|
| 1-4 | Germinal | Implantation, early organ formation |
| 5-8 | Embryonic | Limbs forming, heart begins to beat |
| 9-12 | Fetal | Fingers and toes forming, facial features developing |
| 13-20 | Fetal | Brain development, eye formation, limb movement |
| 21-28 | Fetal | Lung development, fat storage, bone formation |
| 29-40 | Fetal | Maturation, preparation for birth |
The calculator provides a visual timeline chart showing your baby's current position in development.
Baby Development Stages
Each week of pregnancy brings new developments. Here's a quick overview:
- First Trimester (1-12 weeks): Organ formation, rapid growth, and early movement.
- Second Trimester (13-28 weeks): Rapid growth, visible features, and increased activity.
- Third Trimester (29-40 weeks): Maturation, fat storage, and preparation for birth.
Use the calculator to track your baby's progress through these stages.
Common Questions
- How accurate is the gestational age calculator?
- The calculator provides an estimate based on standard pregnancy duration. For precise measurements, consult your healthcare provider.
- Can I use this calculator for multiple pregnancies?
- Yes, you can calculate gestational age for each baby separately by entering their individual LMP or ultrasound dates.
- What if I don't know my LMP date?
- You can use the date of your first prenatal ultrasound instead. The calculator will use this as the starting point.
- How often should I check my baby's gestational age?
- Regular prenatal checkups are recommended every 4 weeks, but you can use this calculator anytime to track progress.
- What if my baby's development seems delayed?
- Consult your healthcare provider if you notice any concerns about your baby's growth or development.