IU to mg Converter
Convert between International Units and milligrams for vitamins and medications. Enter values for instant results with step-by-step formulas.
Formula
Mass = IU x Conversion Factor (substance-specific)
International Units measure biological activity, not mass. Each substance has a unique conversion factor defined by WHO. For example, Vitamin D: 1 IU = 0.025 mcg; Vitamin E (natural): 1 IU = 0.67 mg; Vitamin A (retinol): 1 IU = 0.3 mcg.
Worked Examples
Example 1: Vitamin D Supplement Conversion
Problem: Convert a 5,000 IU Vitamin D3 supplement to micrograms and milligrams.
Solution: Conversion factor: 1 IU Vitamin D = 0.025 mcg\nmcg = 5,000 IU x 0.025 = 125 mcg\nmg = 125 mcg / 1,000 = 0.125 mg\nVerification: 0.125 mg x 40,000 IU/mg = 5,000 IU (correct)
Result: 5,000 IU of Vitamin D3 = 125 mcg = 0.125 mg
Example 2: Natural vs Synthetic Vitamin E
Problem: Compare 400 IU of natural vs synthetic Vitamin E in milligrams.
Solution: Natural (d-alpha): 400 IU x 0.67 mg/IU = 268 mg\nSynthetic (dl-alpha): 400 IU x 0.45 mg/IU = 180 mg\nDifference: 268 - 180 = 88 mg more in natural form\nNatural has 49% more mass per IU due to higher bioactivity
Result: 400 IU natural = 268 mg | 400 IU synthetic = 180 mg (88 mg difference)
Frequently Asked Questions
Does IU to mg Converter work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Is IU to mg Converter free to use?
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Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
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