Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Baby Size Calculator

Estimates fetal weight and size using gestational age alone or ultrasound measurements (BPD, FL, AC). Used by parents and clinicians to track growth against standard developmental charts.

Gestational Age (weeks)

Additional Days (days) (optional)

Biparietal Diameter (BPD) (mm) (optional)

Femur Length (FL) (mm) (optional)

Abdominal Circumference (AC) (mm) (optional)

Fill in the required fields to see your result.

Pregnancy

Due Date Calculator

Estimates how many days remain until your due date and your current pregnancy week from how many days ago your last period (or conception/ultrasound reference) was, plus cycle length and any ultrasound adjustment.

Days Since Last Period (or chosen reference) (days)

Average Cycle Length (days)

Calculation Method

Ultrasound Adjustment (days)

Fill in the required fields to see your result.

Key differences

	Baby Size Calculator	Due Date Calculator
Category	Pregnancy	Pregnancy
Inputs required	5	4
Result	Estimated Baby Weight (grams)	Due Date Countdown
What it does	Estimates fetal weight and size using gestational age alone or ultrasound measurements (BPD, FL, AC). Used by parents and clinicians to track growth against standard developmental charts.	Estimates how many days remain until your due date and your current pregnancy week from how many days ago your last period (or conception/ultrasound reference) was, plus cycle length and any ultrasound adjustment.