Convert IU to mcg or mg, or mcg to IU, for vitamin D (1 IU = 0.025 mcg), vitamin A and vitamin E, with a custom factor for other substances.
IU To mcg Formula
The following formula is used to calculate the conversion from international units (IU) to micrograms (mcg).
Variables:
- mcg is the amount in micrograms
- IU is the amount in international units
- CF is the conversion factor in micrograms per IU for the exact substance, form and output basis; RAE and vitamin E label claim are activity equivalents
To convert IU to micrograms, multiply by the factor for the exact form and basis; reverse by dividing micrograms by that factor. Vitamin A beta-carotene ingredient mass differs from mcg RAE. Natural/synthetic vitamin E label-claim factors describe alpha-tocopherol activity, not total chemical ingredient mass. Vitamin C, unknown mixtures and other substances require a verified custom factor.
| IU | Micrograms (mcg) |
|---|---|
| 50 | 1.250 |
| 100 | 2.500 |
| 200 | 5.000 |
| 400 | 10.000 |
| 600 | 15.000 |
| 800 | 20.000 |
| 1000 | 25.000 |
| 1200 | 30.000 |
| 1500 | 37.500 |
| 2000 | 50.000 |
| 2500 | 62.500 |
| 3000 | 75.000 |
| 4000 | 100.000 |
| 5000 | 125.000 |
| 6000 | 150.000 |
| 8000 | 200.000 |
| 10000 | 250.000 |
| 20000 | 500.000 |
| 50000 | 1250.000 |
| 100000 | 2500.000 |
| * Rounded to 3 decimals. Assumes Vitamin D2 (ergocalciferol) or Vitamin D3 (cholecalciferol): 1 IU = 0.025 mcg (40 IU = 1 mcg). For authoritative guidance, check a reputable reference such as the NIH Office of Dietary Supplements Vitamin D fact sheet or the product label. | |
What is IU To mcg?
IU to mcg is a conversion from International Units (IU) to micrograms (mcg). IU is a measure of biological activity, not a universal mass unit, so the IU↔mcg conversion depends on the specific substance and sometimes the exact form (for example, vitamin A retinol vs beta-carotene, or vitamin E natural vs synthetic forms). Therefore, it’s important to use the correct conversion factor from a trusted source for what you’re converting.
How to Calculate IU To mcg?
The following steps outline how to calculate the IU To mcg using the formula: mcg = IU * CF.
- First, determine the amount in International Units (IU).
- Next, choose the exact substance, form and ingredient/RAE/label-claim basis, or supply a verified custom factor. Ensure the input mass uses the same basis.
- Next, use the formula mcg = IU * CF to calculate the amount in micrograms (mcg).
- Finally, calculate the IU To mcg.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Vitamin D3 amount in International Units (IU) = 500
Conversion Factor (CF) (Vitamin D3) = 0.025 mcg/IU → mcg = 500 × 0.025 = 12.5 mcg
