An FTU of cream or ointment is measured on an adult index finger before being rubbed onto a child. Again, one FTU is used to treat an area of skin on a child equivalent to twice the size of the flat of an adult's hand with the fingers together. You can gauge the amount of topical steroid to use by using your (adult) hand to measure the amount of skin affected on the child. From this you can work out the amount of topical steroid to use.

The following gives a rough guide:

For a 3-6 month old child

• Entire face and neck - 1 FTU
• An entire arm and hand - 1 FTU
• An entire leg and foot - 1.5 FTUs
• The entire front of chest and abdomen - 1 FTU
• The entire back including buttocks - 1.5 FTUs

For a 1-2 year old child

• Entire face and neck - 1.5 FTUs
• An entire arm and hand - 1.5 FTUs
• An entire leg and foot - 2 FTUs
• The entire front of chest and abdomen - 2 FTUs
• The entire back including buttocks - 3 FTUs

For a 3-5 year old child

• Entire face and neck - 1.5 FTUs
• An entire arm and hand - 2 FTUs
• An entire leg and foot - 3 FTUs
• The entire front of chest and abdomen - 3 FTUs
• The entire back including buttocks - 3.5 FTUs

For a 6-10 year old child

• Entire face and neck - 2 FTUs
• An entire arm and hand - 2.5 FTUs
• An entire leg and foot - 4.5 FTUs
• The entire front of chest and abdomen - 3.5 FTUs
• The entire back including buttocks - 5 FTUs

这里是文章的链接，有图示用量单位

http://www.patient.co.uk/health/Fingertip-Units-for-Topical-Steroids.htm