Note: This tool checks your baby’s height and head circumference percentiles together, so use the Baby Weight Percentile Calculator instead when you only want to check weight, or the Baby Height and Weight Percentile Calculator when you also want to check weight.
Baby Height and Head Circumference Percentile Calculator
Check your baby's length and head size against the WHO Child Growth Standards for their age and sex.
Born early? (optional, corrected age)
For babies born before 37 weeks, growth is usually plotted by corrected age until 24 months.
A percentile is not a grade. The 50th percentile is the middle, and healthy babies can be anywhere from the 2nd to the 98th. Doctors look at the pattern over several visits, and at birth history and parents' heights. Based on the WHO Child Growth Standards. Please talk to your doctor if you are worried.
How to use
- Choose cm or inches, and select boy or girl.
- Enter your baby's date of birth (or age in months) and the date of measurement.
- Enter length, head circumference or both. One is enough.
- Press Calculate to see percentiles, status and a growth chart.
- Tap the chart buttons to switch between length and head size.
Baby Height and Head Circumference Percentile Calculator
Is Your Baby’s Head Size Normal?
At every baby check-up, the doctor wraps a soft tape around your baby’s head. Parents often wonder why. Head size is one of the key signs of healthy growth in the first two years. Our free baby height and head circumference percentile calculator compares your baby’s head size and length with WHO standards.
Why Is Head Circumference Measured?
Head circumference is the distance around the widest part of the head. In babies, it reflects how fast the brain and skull are growing. The first year brings the fastest growth.
According to WHO data, a boy’s head grows from about 34.5 cm at birth to 46.1 cm at 12 months. That is almost 12 cm in one year. A girl’s head grows from about 33.9 cm to 44.9 cm over the same time.
Average Head Circumference and Length by Age
The table shows the WHO median, with the 3rd to 97th percentile range in brackets. Almost all healthy babies fall inside this range.
Boys
| Age | Head circumference (median) | Length (median) |
|---|---|---|
| Birth | 34.5 cm (32.1 to 36.9) | 49.9 cm (46.3 to 53.4) |
| 1 month | 37.3 cm (35.1 to 39.5) | 54.7 cm (51.1 to 58.4) |
| 3 months | 40.5 cm (38.3 to 42.7) | 61.4 cm (57.6 to 65.3) |
| 6 months | 43.3 cm (41.0 to 45.6) | 67.6 cm (63.6 to 71.6) |
| 9 months | 45.0 cm (42.6 to 47.4) | 72.0 cm (67.7 to 76.2) |
| 12 months | 46.1 cm (43.6 to 48.5) | 75.7 cm (71.3 to 80.2) |
| 24 months | 48.3 cm (45.7 to 50.8) | 87.8 cm (82.1 to 93.6) |
Girls
| Age | Head circumference (median) | Length (median) |
|---|---|---|
| Birth | 33.9 cm (31.7 to 36.1) | 49.1 cm (45.6 to 52.7) |
| 1 month | 36.5 cm (34.3 to 38.8) | 53.7 cm (50.0 to 57.4) |
| 3 months | 39.5 cm (37.2 to 41.9) | 59.8 cm (55.8 to 63.8) |
| 6 months | 42.2 cm (39.7 to 44.6) | 65.7 cm (61.5 to 70.0) |
| 9 months | 43.8 cm (41.3 to 46.3) | 70.1 cm (65.6 to 74.7) |
| 12 months | 44.9 cm (42.3 to 47.5) | 74.0 cm (69.2 to 78.9) |
| 24 months | 47.2 cm (44.6 to 49.8) | 86.4 cm (80.3 to 92.5) |
Boys are slightly larger on average at every age. Even so, the healthy range is wide for both.
How to Read the Percentile
A percentile compares your baby with others of the same age and sex. For head size, the 50th percentile means half of babies have a smaller head, and half have a larger one. It does not rate your baby.
The WHO charts treat the 2nd and 98th percentiles as the outer limits. A baby outside this range is not necessarily unwell. However, doctors will usually look more closely.
Head Size and Length Together
A baby’s head and body grow together, but not always at the same rate. For example, a baby with a head on the 80th percentile and a length on the 40th percentile may simply have a larger head. In that case, family size is often the reason.
Doctors compare both values, and they also look at parents’ head sizes and heights. Our calculator shows each result on a chart, so you can see the pattern at a glance.
How to Measure Head Circumference at Home
The American Academy of Pediatrics recommends measuring head size at every visit until the 2-year check-up. To get an accurate number:
- Use a soft, non-stretch tape measure.
- Place it just above the eyebrows and ears, around the widest part of the back of the head.
- Move the tape slightly up and down to find the maximum measurement.
- Record it to the nearest 0.1 cm.
- Measure two or three times and use the largest value.
For length, measure your baby lying down until 24 months. If you measured standing, add 0.7 cm. The calculator can adjust this for you.
Why Does Head Growth Matter?
Steady head growth suggests a baby is developing normally. A head that grows much faster or slower than expected can point to a problem that needs checking. Doctors may order a scan or further tests in such cases.
Do not panic over one reading. Measuring errors and differences between tape measures are common. What matters most is the trend over several visits. A baby who stays near the same percentile is usually growing as expected.
Premature Babies
Babies born before 37 weeks are usually plotted by corrected age until about 24 months. Corrected age means actual age minus the weeks born early. Use the Baby Age Calculator to find both ages, then enter the birth week in the percentile calculator.
When to Talk to Your Doctor
Speak to your doctor if:
- Your baby’s head size is below the 2nd or above the 98th percentile
- The percentile changes quickly across two major lines over a few months
- The soft spot on top of the head looks swollen, or very sunken
- Your baby is unusually sleepy, vomits often or feeds poorly
Related Tools
Growth begins before birth. See your baby’s size each week with Baby Size by Week and the Pregnancy Week by Week Calculator. Work out your dates with the Due Date Calculator, the Gestational Age Calculator and the Ultrasound Due Date Calculator.
Healthy eating helps too. Try the Pregnancy Calorie and Protein Calculator, the Pregnancy Weight Gain Calculator and the BMI Calculator. If you are still planning, the Ovulation Calculator, Safe Period Calculator, Pregnancy Test Date Calculator, Conception Due Date Calculator and IVF Due Date Calculator can help.
Closer to birth, use the Kick Counter, Contraction Timer and Hospital Bag Checklist. After the birth, plan feeds with the Baby Feeding Reminder, and see your baby’s weight with our Baby Height and Weight Percentile Calculator. Wondering about the future? The Baby Adult Height Predictor, Baby Budget Calculator and Baby Name Generator are fun next steps.
Frequently Asked Questions
What is a normal head circumference for a newborn?
At birth, the WHO median is about 34.5 cm for boys and 33.9 cm for girls. Most healthy newborns fall between about 32 and 37 cm.
How much does a baby’s head grow in the first year?
About 12 cm in boys and 11 cm in girls, with most growth in the first six months.
Is a big head percentile a problem?
Not always. A large head can run in the family. Doctors check the trend and compare it with length and parents’ head sizes.
Why is head size measured only until age 2?
Brain growth is fastest in the first two years, so this is when the measurement is most useful.
Can I measure my baby’s head at home?
Yes, with a soft tape measure. However, clinic measurements are more reliable, so share your numbers with your doctor.
Sources: WHO Child Growth Standards; CDC, Use and Interpretation of the WHO and CDC Growth Charts; American Academy of Pediatrics guidance on anthropometric measurements.