International Units (IU) are used to measure vitamin potency. The formula for calculating IU depends on the substance being measured. Use the guidelines below to compare labels.

Beta Carotene

1 mg beta-carotene = 1667 IU

Sample Conversion

Q: If a beta-carotene supplement claims 9 mg per tablet, how many IUs is that?

A: 9 mg X 1667 IU/mg = 15,000 IU

Vitamin E

The conversion process varies for vitamin E depending on the carrier:

• 1 IU d-alpha tocopherol = 0.67 mg
• 1 mg d-alpha tocopherol = 1.49 IU
• 1 IU d-alpha tocopheryl succinate = 0.83 mg
• 1 mg d-alpha tocopheryl succinate = 1.21 IU
• 1 IU d-alpha tocopheryl acetate = 0.74 mg
• 1 mg d-alpha tocopheryl acetate = 1.36 IU

Sample Conversion

Q: How many milligrams of vitamin E does my supplement contain if it states 400 IU d-alpha tocopherol?

A: 400 IU d-alpha tocopherol X .67 mg/IU = 268 mg

Vitamin D

• 1 mcg = 40 IU
• 1 IU vitamin D = 0.025 micrograms of cholecalciferol

Sample Conversion

Q: How many micrograms does a supplement have if the label says 400 IU vitamin D?

A: 400 IU vitamin D / 40 mcg/IU = 10 mcg vitamin D