Forgotten Diseases Research Foundation

Head Circumference Calculator

Use this tool to get an idea about head size in comparison to other people of your race or ethnicity. In babies and children, measuring head size is an important way to track brain growth. It's also useful for identifying sudden changes in head size (such as when there is a brain tumor). Please note that although the data in this tool come from peer-reviewed studies, it can't be used to diagnose a disease. See your doctor if you think something is not right with you or your child.

Please provide some information about yourself or your child. We don't record or keep any information you enter here. The categories for Mixed Race and Race/Ethnicity not on this list" use data from the World Health Organization.

Basic information




National Origin, Race or Ethnicity

Please select the country that best describes your origin. Bear in mind that the WHO data skews toward lower values. These categories are limited by the availability of data, but we will be adding more categories to the calculator over time.

Important notes:

  • When you pick your country or ethnicity, you will also see what kind of data we have.
  • Gest. Age means the number of complete weeks a pregnancy lasted (For 38 weeks and 6 days, choose 38 weeks).
  • Postnatal means growth after a child is born.
  • If you see "Postnatal, 0-5 years, monthly," this means we have data points for each month from Birth (0 months) to 5 years (60 months).
  • You can enter 1 Year, 1 month, or 13 months.

Head size:

  • Enter as many measurements as you like.
  • Please include zeros, as in 0 years, 8 months or 2 years, 0 months.
  • For head size at birth, write 0 years, 0 months.
  • Write 1/2 as 0.5
  • Write 1/4 as 0.25
  • Write 3/4 as 0.75

Gestational Age at Birth



  Completed Weeks Gestation:     Head size:    cm  




  Years:     Months:       Head size:    cm  
  Years:     Months:       Head size:
  Years:     Months:       Head size:
  Years:     Months:       Head size:
  Years:     Months:       Head size:

References for data used here may be found on our calculator references page.

Page last modified on 5 April 2022.