Baby Growth Rate Calculator - Weight, Length and Head Tracker

Enter baby measurements

Baby name

Sex

Date of birth

First measurement date

Second measurement date

Weight unit

First weight

Second weight

Length unit

First length

Second length

Head circumference unit

First head circumference

Second head circumference

Custom minimum target gain (g/day)

Custom maximum target gain (g/day)

Projection days

Example data table

Baby	Measurement 1	Measurement 2	Days	Weight gain	Daily gain	Length gain	Head gain
Sample Infant	Jan 05, 2026 5.10 kg, 57.0 cm, 39.2 cm	Feb 16, 2026 6.00 kg, 60.5 cm, 40.7 cm	42	0.90 kg	21.43 g/day	3.50 cm	1.50 cm
Sample Infant	Mar 01, 2026 6.00 kg, 60.5 cm, 40.7 cm	Apr 05, 2026 6.70 kg, 63.0 cm, 41.8 cm	35	0.70 kg	20.00 g/day	2.50 cm	1.10 cm

These rows are examples only. Actual growth patterns vary by age, birth history, feeding, and individual development.

Formula used

1) Total weight gain

Weight gain = second weight − first weight

2) Average daily weight gain

Daily gain (g/day) = [(second weight − first weight) × 1000] ÷ number of days

3) Percentage change

Percentage change = [(new value − old value) ÷ old value] × 100

4) Compound daily growth rate

CDGR = [(second weight ÷ first weight)^(1 ÷ days) − 1] × 100

5) Growth velocity for length or head size

Monthly velocity = [(second value − first value) ÷ days] × 30.4375

6) Ponderal index

Ponderal index = weight in kilograms ÷ length in meters³

7) Linear projection

Projected weight = current weight + (daily gain × future days)

This tool helps track change between two measurements. It does not diagnose feeding issues, illness, or growth disorders.

How to use this calculator

Enter the baby’s first and second measurement dates.
Add weight, length, and head circumference for both dates.
Select the correct units for each measurement type.
Optionally enter birth date to show age at each record.
Optionally set custom minimum and maximum daily gain targets.
Enter projection days to estimate future weight using current pace.
Press Calculate Growth Rate to view the summary above the form.
Use the chart, results table, CSV export, and PDF export for review or recordkeeping.

Frequently asked questions

1) What does this calculator measure?

It compares two baby measurement records and calculates weight gain, daily growth rate, percentage change, length growth, head circumference growth, and simple projections.

2) Can I use pounds and inches?

Yes. The calculator accepts kilograms or pounds for weight, and centimeters or inches for length and head circumference. It converts values internally for consistent formulas.

3) Why are dates required?

Growth rate depends on elapsed time. Two measurements with the same change can imply very different daily growth rates if the number of days differs.

4) What is compound daily growth rate?

It estimates the average percentage increase per day using a compounding model. This can be useful when reviewing relative growth instead of only absolute gain.

5) What is ponderal index?

Ponderal index relates weight to body length. It is similar to a body proportionality check and may help compare two measurements over time.

6) Is the projection feature a medical forecast?

No. It is only a straight-line estimate based on the current average rate. Real baby growth usually changes over time and should not be assumed linear.

7) Should I worry if a value decreases?

First recheck the entered dates, units, and measurements. If the numbers are correct and the decrease is unexpected, discuss it with a pediatric professional.

8) Can this replace a doctor’s assessment?

No. This tool supports recordkeeping and trend review. Clinical growth evaluation should consider age, history, feeding, percentiles, and professional examination.