Baby Weight in Womb Calculator

Pregnancy is a remarkable journey, and tracking your baby's growth is an important part of the experience. One of the most fascinating aspects of fetal development is the steady increase in weight. This calculator helps you estimate your baby's weight in the womb based on your pregnancy week.

How to Use This Calculator

Using our baby weight in womb calculator is simple:

Enter your current pregnancy week (1-40)
Select your baby's sex (optional)
Click "Calculate" to see your baby's estimated weight
Review the growth chart and interpretation

The calculator provides an estimate based on average fetal growth patterns. For precise measurements, consult your healthcare provider.

Fetal Weight Formula

The calculator uses a modified version of the Hadlock formula, which is widely accepted in obstetrics:

For weeks 1-13:

Weight (grams) = (Week × 10) + 100

For weeks 14-40:

Weight (grams) = (Week × 20) + 100

This formula provides a general estimate. Actual fetal weight can vary based on individual factors.

Fetal Growth Patterns

Fetal growth follows predictable patterns throughout pregnancy:

First trimester (1-13 weeks): Rapid growth in size and weight
Second trimester (14-27 weeks): Steady increase in all measurements
Third trimester (28-40 weeks): Slower growth as baby prepares for birth

Here's a general growth table:

Week	Estimated Weight (grams)	Estimated Weight (ounces)
1	110	3.9
10	300	10.6
20	1,100	38.6
30	2,100	74.1
40	3,100	109.4

Interpreting Results

When you calculate your baby's estimated weight, consider these factors:

Normal weight range for a full-term baby: 2,500-4,500 grams (8.8-15.7 ounces)

Premature babies (under 37 weeks) typically weigh less than 2,500 grams

If your baby's estimated weight is significantly below or above the average, it may be worth discussing with your healthcare provider. However, remember that individual variations are normal.

Frequently Asked Questions

Is this calculator accurate for all pregnancies?: This calculator provides a general estimate based on average growth patterns. Actual fetal weight can vary significantly between individuals. For precise measurements, consult your healthcare provider.
Why does my baby's weight change so much between weeks?: Fetal growth is highly variable. Some weeks show more growth than others, and individual differences are normal. The calculator shows average trends rather than exact measurements.
When should I be concerned about my baby's weight?: Consult your healthcare provider if your baby's estimated weight is significantly below or above the average for your pregnancy week, or if you have any other concerns about fetal growth.
Can I track my baby's weight over time?: Yes! Use this calculator each week to see how your baby's estimated weight changes throughout pregnancy. You can also track actual measurements provided by your healthcare provider.