Baby Growth Calculator

Free Baby Growth Calculator

Use this free baby growth calculator to see how much weight your baby has gained since birth, and how that compares to typical weekly weight-gain rates for their age. Enter your baby's date of birth, birth weight, and current weight to get started.

Babies typically gain weight fastest in the first few months of life, then more gradually as they approach their first birthday. This calculator uses widely published average ranges by age band to give you a general sense of whether your baby's recent weight gain looks typical. It is not a substitute for the growth charts your pediatrician uses, which track your baby's own individual percentile curve over time rather than a single average rate.

How to Use the Baby Growth Calculator

• Choose Imperial or Metric units.
• Enter your baby's date of birth.
• Enter your baby's birth weight and current weight.
• Click Calculate Growth to see your baby's age, total weight gained, and how their average weekly gain compares to the typical range.

Features

• Supports both Imperial (lb, oz) and Metric (kg) units.
• Calculates total weight gained and average weekly gain since birth.
• Compares your baby's gain to typical ranges by age band.
• Mobile-friendly with print, share, copy, and download options.

Frequently Asked Questions

How much weight should a baby gain each week?

As a general guide, babies typically gain about 140 to 200 grams (5 to 7 oz) per week in the first 3 months, 85 to 140 grams (3 to 5 oz) per week from 3 to 6 months, 40 to 85 grams (1.5 to 3 oz) per week from 6 to 12 months, and 30 to 60 grams (1 to 2 oz) per week from 12 to 24 months. Individual babies vary quite a bit within these ranges.

Is this calculator the same as a growth chart my pediatrician uses?

No. Pediatricians use WHO or CDC growth charts that plot your baby's individual percentile over time based on precise reference data. This calculator gives a simpler, general comparison against typical weight-gain rates and is meant as a rough guide only.

What if my baby's weight gain is outside the typical range?

A single measurement outside the typical range is common and not automatically a cause for concern, especially since growth is not perfectly linear. However, if you're consistently seeing low or unusually high weight gain, or have any concerns, talk to your pediatrician, who can assess your baby's full growth history.

Is this calculator free?

Yes, this baby growth calculator is completely free to use with no sign-up required.

Related Calculators

Want to know your baby's exact age in days, weeks, or months? Try our baby age calculator. Curious about their age in months specifically? Use the age in months calculator. Tracking a milestone like their half birthday? Check the half birthday calculator. Still pregnant and tracking your own weight gain? Try our pregnancy weight gain calculator. Want a countdown to their next birthday? Use the birthday countdown calculator.