This free mass converter changes micrograms (µg, also written mcg) into milligrams (mg) and back again, updating live as you type. It is commonly used to read supplement and medication labels, where doses may be quoted in either unit.
How it works
The relationship between the two metric mass units is exact: 1 mg = 1000 µg. The conversion is therefore a simple power-of-ten shift:
- mg = µg ÷ 1000
- µg = mg × 1000
The relationship is linear, so the converter is bidirectional — edit either field and the other updates instantly. Note that “mcg” is just another way to write “µg”.
Why µg and mg appear on the same product label
Regulatory standards vary by jurisdiction and product type. Vitamin and mineral labelling in the US historically used micrograms (µg or mcg) for nutrients like folate, vitamin B12, vitamin D, and vitamin K, while medications are more commonly labelled in milligrams. International products sometimes switch between the two units for the same nutrient depending on where they are sold.
The microgram is also preferred when the active dose is very small. A typical vitamin D supplement might contain 25 µg (which is 0.025 mg) — the microgram figure is cleaner to read than a four-decimal milligram value.
Common dose reference table
| Nutrient / substance | Typical dose | Equivalent |
|---|---|---|
| Folic acid (prenatal) | 400 µg | 0.4 mg |
| Vitamin B12 | 2.4 µg | 0.0024 mg |
| Vitamin D | 10–25 µg | 0.01–0.025 mg |
| Biotin | 30 µg | 0.03 mg |
| Ibuprofen (OTC tablet) | — | 200 mg (= 200,000 µg) |
| Melatonin | — | 1–5 mg (= 1,000–5,000 µg) |
These are illustrative common values, not medical recommendations.
Practical worked examples
Example 1. A vitamin D supplement is labelled 2000 IU, with a note that the serving is 50 µg. You want to compare it to a product labelled in mg: 50 ÷ 1000 = 0.05 mg.
Example 2. A research paper gives a dosage as 0.25 mg and you want to express it in micrograms: 0.25 × 1000 = 250 µg.
Example 3. A label says 400 mcg of folic acid per tablet. How many mg? 400 ÷ 1000 = 0.4 mg.
| Micrograms (µg) | Milligrams (mg) |
|---|---|
| 100 µg | 0.1 mg |
| 400 µg | 0.4 mg |
| 500 µg | 0.5 mg |
| 1000 µg | 1 mg |
| 2500 µg | 2.5 mg |
All calculations run entirely in your browser — no data is sent to any server.