IU to mcg Vitamin D3 Converter (Free)

The conversion factor for Vitamin D3 is 1 mcg = 40 IU (or 1 IU = 0.025 mcg). This is the standard conversion used on supplement labels.

The conversion factor (1 mcg = 40 IU) is typically the same for both Vitamin D2 and D3 for label conversion purposes. However, D2 and D3 have different biological activities. This tool is for unit conversion only, not for comparing biological effects.

Some sources use slightly different conversion factors, but 1 mcg = 40 IU is the standard used by the US FDA and most supplement manufacturers on their labels. This tool uses the standard 40:1 ratio.

Yes, this tool converts any amount between IU and mcg. Enter your supplement's dose in one unit to see it in the other. Remember: this is a unit conversion tool only, not a dose recommendation tool.

Common supplement doses include 400 IU (10 mcg), 800 IU (20 mcg), 1000 IU (25 mcg), 2000 IU (50 mcg), 4000 IU (100 mcg), 5000 IU (125 mcg), and 10000 IU (250 mcg). The tool shows a table of these common conversions.

The warning appears when you enter very high values (25,000+ IU or 625+ mcg) to remind you to double-check the units on your label. This helps prevent errors from misreading IU vs mg/mcg.