Body length while lying flat
Use recumbent length for infants from birth through 24 months.
WHO birth to 24 months
Enter infant measurements
WHO reference chart
Use the same day's measurements when comparing the three indicators.
Recumbent length-for-age
the 50th percentile74.0 cm at 12 months on the WHO girls standard.
3rd69.2 cm50th74.0 cm97th78.9 cm
These are three separate age-based indicators. They do not by themselves diagnose nutrition, growth, or health.
Birth to 24 months · WHO standards
Infant Percentile Calculator
Enter age, sex, recumbent length, weight, and head circumference to calculate three WHO growth percentiles and z-scores. Each result is a reference position, not a diagnosis or a forecast.
Three related indicators
What does an infant growth percentile mean?
An infant growth percentile compares one measurement with the WHO standard for children of the same completed month and sex. This growth percentile calculator keeps length, weight, and head circumference separate because they describe different dimensions.
Weight compared with age
The weight percentile calculator result here is weight-for-age, not weight-for-length.
Largest circumference around the head
A correctly placed, non-stretch tape is essential for a useful comparison.
Understand the visual result
How to read an infant percentile chart
An infant percentile chart shows where one measurement sits within the WHO reference for babies of the same completed month and sex. The marker in this calculator summarizes that position; it is not a diagnosis and it does not combine all measurements into one score.
Choose one indicator
Read the length, weight, and head-circumference results separately. A baby can be at different percentiles for each because every measurement uses its own WHO reference distribution.
Read the percentile as a rank
The 50th percentile is the median. A result at the 25th percentile means the measurement equals or exceeds about 25% of the matching reference group; it does not mean 25% growth or 25% health.
Look for a pattern, not a perfect line
The meaning of a baby's percentile comes from repeated, accurate measurements in context. Clinicians look at the direction of the growth pattern, measurement quality, gestational age, feeding, and health history.
Three measurements, three questions
Infant length and weight percentiles answer different questions
People often look for an infant height and weight percentile calculator, but babies under age 2 are measured lying down, so the correct measure is recumbent length rather than standing height. This page reports length-for-age and weight-for-age as separate results.
How long is the infant for their age?
Length is taken on a length board while the baby lies flat. Do not compare this number directly with a standing-height percentile, because the measurement method and reference chart are different.
How heavy is the infant for their age?
This result compares weight with age. It is not weight-for-length, body mass index, or a feeding recommendation, and it should not be interpreted as though those indicators are interchangeable.
How does head size compare with age?
The tape must follow the largest circumference around the head. Because placement can change the result, a concerning value should be rechecked and interpreted by a qualified health professional.
Follow the growth pattern
What baby percentiles mean over time
One percentile is a snapshot. A series of measurements can show how an infant is growing, but only when the age, equipment, and technique are dependable. Normal measurement variation can move a result even when the baby's underlying growth pattern has not changed.
Record the date and measurement method
Use completed months and measurements from the same day when comparing indicators. Recheck an unexpected value before assuming that a short-term percentile shift represents a growth change.
Corrected age may matter in clinical care
Health professionals may use corrected age when assessing some infants born early. This calculator uses the completed month you enter and cannot decide whether an age adjustment is appropriate.
Ask about a persistent or concerning pattern
A clinician can interpret the pattern across length, weight, and head circumference together with feeding, birth history, and health information that a browser calculator does not have.
Calculation method
How are WHO infant percentiles calculated?
The calculator selects the WHO L, M, and S parameters for the chosen sex and completed month. It calculates a z-score for each measurement and converts that score to a percentile. For values beyond ±3, it uses the WHO restricted LMS tail method.
The three results update in the browser. The tool does not request a name or birth date and does not save the measurements.
Completed months from birth through month 24 identify the age-specific parameters.
Length, weight, and head circumference each use their own WHO standard.
The chart marker shows the active measurement on its reference distribution.
Measurement quality
How to measure infant length, weight, and head circumference
Use recent measurements taken with appropriate infant equipment. Small errors can change the percentile, especially at young ages.
- 1
Record completed months
Choose the age reached, not the next month the infant is approaching.
- 2
Measure recumbent length
Use a length board with the head fixed and legs gently straightened.
- 3
Use an infant scale
Remove heavy clothing and record the stable weight before rounding.
- 4
Place the tape at the largest head circumference
Keep a non-stretch tape level above the eyebrows and around the widest point.
Primary sources
WHO Child Growth Standards and limits
This page uses the WHO Child Growth Standards parameters for length-for-age, weight-for-age, and head-circumference-for-age from birth through 24 months. It does not combine those indicators into one health score.
A standing-height percentile chart answers a different question and should not replace recumbent length for an infant. For a U.S. child age 2 or older, use the CDC stature-for-age calculator instead.
Infant percentile FAQ
Common questions about infant growth results
What does an infant percentile mean?
It shows where one measurement falls in the WHO reference distribution for infants of the same completed month and sex. Each indicator has its own percentile, so length, weight, and head circumference may have different results.
Should I use length or standing height for a baby?
Use recumbent length—measured while the infant lies flat—for this birth-to-24-month calculator. Standing height belongs on a different chart and is normally used after age 2.
Is weight percentile the same as weight-for-length?
No. This page calculates weight-for-age. Weight-for-length compares weight with the infant’s measured length and answers a different question, so it should not be labeled as the same percentile.
Can one growth percentile diagnose a health problem?
No. A percentile and z-score describe statistical position. Clinicians consider repeated measurements, measurement quality, feeding, health history, gestational age, and the pattern across indicators.