There is great confusion regarding the ratio of IU’s, which is an International Unit to milligrams when trying to convert between the two. It doesn’t help that each vitamin has a different IU calculation. The majority of the time fat soluble vitamins are listed in international units (IU). On rare occasions, they may appear in metric units, which totally confuses everyone. Once you know the equivalents, it's fairly simple to convert IU to mg, then all you need is pen and paper.

Below is a conversion chart which we hope will make things a little clearer!

Vitamin E

Natural
1 IU = 0.735 mg d-alpha Tocopheryl Acetate
1 IU = 0.671 mg d-alpha Tocopherol
1 IU = 0.861 mg d-alpha Tocopheryl Succinate

Synthetic
1 IU = 1 mg dl-alpha Tocopheryl Acetate
1 IU = 0.91 mg dl-alpha Tocopherol


Vitamin A Acetate

1 IU = 0.344 mcg

Vitamin D

1 IU = 0.025 mcg
40 IU = 1 mcg

Vitamin C

1 IU is 50 μg L-ascorbic acid