How the calculation works
IU vitamin D = mcg × 40
A worked example
25 mcg of vitamin D equals 1,000 IU. A 50 mcg label describes 2,000 IU, and a 100 mcg label describes 4,000 IU.
Compare the same amount of vitamin D
A 25 mcg product and a 1,000 IU product state the same vitamin D amount. To compare value, also check the number of servings in the bottle and the price. A stronger serving is not automatically a better choice.
mcg to IU conversion table for vitamin D
These are equivalent amounts, not suggested doses.
| mcg | IU |
|---|---|
| 5 | 200 |
| 10 | 400 |
| 15 | 600 |
| 20 | 800 |
| 25 | 1,000 |
| 50 | 2,000 |
| 100 | 4,000 |
| 125 | 5,000 |
Common questions
Does this work for vitamin D3 and D2?
Yes. For vitamin D label conversions, 1 mcg equals 40 IU for either form.
Does this work for vitamin A or E?
No. IU conversion factors depend on the vitamin and sometimes its form. Do not use the vitamin D factor for other nutrients.
Is this a vitamin D blood test calculator?
No. Supplement amounts in IU or mcg differ from blood concentrations such as ng/mL or nmol/L. Ask your clinician to interpret a blood result.
Reference: NIH Office of Dietary Supplements: vitamin D. Reviewed .