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How to measure head circumference

A correct measurement takes a minute. Here is the method doctors use, for babies and adults alike.

Head circumference percentile calculator

Sex

Enter the head circumference to see the percentile.

Data: WHO Child Growth Standards (0 to 24 months) and CDC growth charts (24 to 36 months).

What you need

  • A flexible tape that does not stretch. Paper or plastic tapes are best, because cloth tapes stretch over time.
  • A second person to help with a baby or a young child.
  • Something to write the result down.

Step by step

  • Sit an older child or adult upright, looking straight ahead. Lay a baby on their back or hold them on a lap.
  • Place the tape just above the eyebrows, above the ears and around the most prominent part of the back of the head.
  • Pull the tape snug so it presses the hair flat.
  • Read the measurement where the tape overlaps, to the nearest 0.1 cm or ⅛ in.
  • Take the tape off and repeat twice more. Record the largest of the three readings.

Common mistakes

  • Placing the tape too low at the back, below the widest point.
  • Tilting the tape so it sits higher on one side.
  • Measuring over a hair clip, bun or hat.
  • Using a stretchy sewing tape.

How to measure your head

  1. 1 Use a soft tape measure, or a string and a ruler.
  2. 2 Wrap it around your head where the hat will sit: about 1 cm (⅜ in) above your ears and across the middle of your forehead.
  3. 3 Keep the tape level and snug, not tight. Do not pull it in.
  4. 4 Read the number where the tape overlaps. Measure two or three times and use the largest value.
  5. 5 Type the number into the calculator, or find it in the chart.
How to measure

Frequently asked questions

Where do you measure head circumference?

Around the widest part of the head: just above the eyebrows and ears at the front and sides, and over the most prominent point at the back.

How tight should the tape be?

Snug enough to press the hair flat. For a hat size, measure a little looser, the way the hat will sit.

How often should a baby’s head be measured?

Doctors usually measure it at each routine checkup in the first two years.

Related charts

All charts