A soft tape. One useful number.

Make the measurement, not an age estimate

Use a flexible measuring tape and follow the hat maker’s method. Green Sprouts describes measuring above the eyebrows and around the widest part at the back of the head. Record the unit and the result together. This is a hat-shopping measurement, not a medical assessment of growth.

Measurement method: Green Sprouts sizing information ↗.

Keep the tape in the intended position

Take time to check that the tape follows the intended path rather than sliding down at the back or sitting at a different angle each time. Repeat if the child moves or the reading is uncertain. Do not force a measurement; return to it when the child is comfortable.

Use the exact chart

Open the source chart for the model you are considering. Check whether its figures describe head circumference, a garment measurement, a maximum or a range. Our finder only checks published minimum and maximum circumference ranges that we could verify. It does not calculate a size from age.

Try a boundary example

For an illustrative 44 cm measurement, Sunday Afternoons’ two infant ranges, 38–44 cm and 44–47 cm, both include the number. Keep both on the shortlist; the chart alone does not select one. If the tape reads 18 inches, record the unit: that converts to 45.72 cm, rather than 18 cm. These are worked examples, not measurements taken from a child. Repeat an uncertain reading and use the exact model’s fit instructions.

Record what remains to check

A matching number is a shortlist, not a fit guarantee. Check the maker’s adjustment and use instructions, the actual hat and how it sits. If your reading is at a shared boundary, both listed ranges may appear. Ask the maker when the chart does not resolve the choice.