What cap sizes are available and how do I choose the right size?

How to Measure Head Circumference

To choose the correct EEG cap size, measure the patient's head circumference before the EEG recording.

• Ask the patient to sit comfortably with their head in a neutral position.
• Place the measuring tape around the head approximately 3 cm (1.2 inches) above the eyebrows at the forehead.
• Keep the tape flat and measure the full circumference of the head.
• Use the measurement to select the appropriate cap size.

Available EEG Cap Sizes

The following EEG cap sizes are available:

• Small: Head circumference from 50 to 54 cm (19.7 to 21.3 inches). Small caps are identified by a yellow size tag.
• Medium: Head circumference from 54 to 58 cm (21.3 to 22.8 inches). Medium caps are identified by a red size tag.
• Large: Head circumference from 58 to 62 cm (22.8 to 24.4 inches). Large caps are identified by a blue size tag.

Selecting the Correct Cap Size

• Select the cap size that matches the measured head circumference.
• Verify the cap size using the size tag on the cap.
• Use the color tag as a quick visual reference.
• Do not estimate cap size based on appearance alone.
• Confirm that the cap fits securely while remaining comfortable for the patient.

Why Correct Cap Size Matters

Selecting the correct cap size helps ensure:

• Proper cap positioning and alignment.
• Stable sponge-to-scalp contact.
• Patient comfort throughout the recording.
• Reliable EEG signal acquisition.

A cap that is too loose may shift during recording and affect electrode contact. A cap that is too tight may be uncomfortable and more difficult to position correctly.

Notes

• Always measure head circumference before selecting a cap.
• Use the measured head circumference to determine the correct size.
• Verify both the size tag and color tag before placing the cap on the patient.
• Confirm that the cap is secure, comfortable, and correctly aligned before continuing with EEG setup.