mcg to IU converter | Convert IU to mcg

The mcg to IU converter is an online tool that can help you convert the strength of your vitamins A, D₃, E, and folate (B9) from micrograms (mg) to International Units (IU) and also from IU to mg. It is very easy to use as you’ll see.

What is IU?

IU stands for International Units and is a standard measure used to quantify the biological activity or amount of certain vitamins. 

For the fat-soluble vitamins A, D and E, along with some B vitamins like folic acid, IU indicates the precise quantity needed to produce a specific biological effect for that vitamin type. 

Using IU allows standardized measurements so dosages and recommendations remain aligned globally across countries.

Why is IU used?

The IU scale was established to account for variability in potency of different forms of certain vitamins. While mass units like milligrams are fixed and exact, the IU more accurately reflects true biological activity – the amount actually available for our bodies to utilize. 

For example, 1 IU of natural retinol vitamin A tends to be better absorbed than 1 IU of supplemental beta carotene vitamin A precursor. So the IU indicates the functional “strength” rather than just mass quantity. This helps ensure products have adequate activeness.

How does converting from mcg to IU work for Vitamin A, D3, E, and Folate?

To convert from mcg to IU, you need a conversion factor. The following are the conversion factors for the various vitamin types:

1. Vitamin A
   • 1 IU = 0.3 mcg retinol
   • 1 mcg retinol = 3.33 IU
2. Vitamin D3
   • 1 IU = 0.025 mcg cholecalciferol
   • 1 mcg cholecalciferol = 40 IU
3. Vitamin E
   • 1 IU = 0.67 mg d-alpha-tocopherol
   • 1 mg d-alpha-tocopherol = 1.5 IU
4. Folate
   • 1 mcg = 0.6 IU folate
   • 1 IU folate  = 1.67 mcg

Vitamins Conversion Chart

Vitamin A – IU to mcg / mcg to IU Conversion Chart
To convert from IU of Vitamin A to mcg RAE (Retinal Activity Equivalents), multiply IU by 0.3
Value in IU	Equivalent value in mcg RAE
2400 mcg	8000 IU
3000 IU	900 mcg
5,000 IU	1500 mcg
10,000 IU	3000 mcg
15,000 IU	4500 mcg
25,000 IU	7500 mcg
900 mcg	3000 IU
7500 mcg	25000 IU
700 mcg	2333 IU

Vitamin D3 – IU to mcg / mcg to IU Conversion Chart
To convert from IU of Vitamin D to mcg, multiply IU by 0.025
Value in IU	Equivalent value in mcg
400 IU	10 mcg
500 IU	12.5 mcg
800 IU	20 mcg
1000 IU	25 mcg
2000 IU	50 mcg
3000 IU	75 mcg
4000 IU	100 mcg
5,000 IU	125 mcg
10,000 IU	250 mcg
50,000 IU	1250 mcg

Vitamin E – IU to mg / mg to IU Conversion Chart
To convert from IU of Vitamin E to mg d-alpha tocopherol, multiply IU by 0.67
Value in IU	Equivalent value in mg
400 IU	268 mg
800 IU	536 mg
1000 IU	670 mg

Folate – mcg to mcg DFE Conversion Chart
To convert Folic acid and 5-MTHF from mcg to mcg DFE (Dietary Folate Equivalents), divide mcg by 0.6
Value in mcg	Equivalent value in mcg DFE
400 mcg	667 mcg DFE
800 mcg	1333 mcg DFE

References

1. WHO National Institute for Biological Standards and ControlWHO International Standard OXYTOCIN 4th International Standard; April 2013
2. Hewitt W. Theory and application of Microbiological Assay; December 1988
3. World Health Organisation WHO International Biological Reference Preparations; January 2016
4. National Institutes of Health, Office of Dietary Supplements Dietary Supplement Ingredient Database – Unit Conversions; May 2016
5. WHO Expert Committee on Biological Standardization WHO International Collaborative Study of the Proposed 4th International Standard for Prolactin, Human; October 2016