mcg to mg Calculator — Micrograms to Milligrams
Convert micrograms (mcg, µg) to milligrams (mg) or back. Because 1 milligram = 1 000 micrograms, you divide by 1 000 going from mcg to mg, and multiply by 1 000 going from mg to mcg.
Conversion direction
mcg
1 mg = 1 000 mcg • 1 mcg = 0.001 mg
- 1
Metric ratio
1 mg = 1 000 mcg1 mg = 10⁻³ g and 1 mcg = 10⁻⁶ g, so the ratio is exactly 1 000 - 2
Milligrams
500 ÷ 1,000 = 0.500000
How does this calculator work?
Divide mcg by 1 000 to get mg; multiply mg by 1 000 to get mcg. 1 mg = 1 000 mcg. Example: 500 mcg = 0.5 mg. The conversion is a fixed metric ratio and applies to any substance regardless of form.
Formula
How this is calculated
The metric system defines 1 milligram (mg) = 10⁻³ grams and 1 microgram (mcg or µg) = 10⁻⁶ grams, so 1 mg = 1 000 mcg. The conversion is therefore purely a factor-of-one-thousand step: to go from mcg to mg, divide by 1 000; to go from mg to mcg, multiply by 1 000. No rounding or unit-specific constants are needed — it is the same ratio for any substance.
This calculation is common in pharmacy, nutrition and laboratory work where doses are frequently listed in mcg on supplement labels, pharmaceutical package inserts, or blood-test reference ranges, and the prescriber or user needs to compare them with mg-based quantities. For example, a 400 mcg folic acid supplement equals 0.4 mg; 1 000 mg of calcium equals 1 000 000 mcg.
The calculator also shows the equivalent in grams and nanograms (ng) for additional context. One nanogram = 10⁻³ mcg, and one gram = 1 000 mg = 1 000 000 mcg.
Frequently asked questions
1 mg = 1 000 mcg. So 0.5 mg = 500 mcg, and 2.5 mg = 2 500 mcg. To convert mcg to mg, always divide by 1 000.
Yes. mcg is the informal abbreviation and µg is the official SI abbreviation for microgram. They are identical units. Both appear on supplement labels and medical documents, sometimes interchangeably.
Very small doses (e.g. 0.025 mg) are clearer when written as 25 mcg to avoid leading zeros and reduce dosing errors. Larger doses (e.g. 500 mg paracetamol) are inconveniently large as micrograms. Regulatory guidance varies by country and drug category.
Also known as
TG we-Calculate Editorial Team. (2026). mcg to mg Calculator — Micrograms to Milligrams [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/mcg-to-mg-calculator
TG we-Calculate Editorial Team. "mcg to mg Calculator — Micrograms to Milligrams." TG we-Calculate. 2026. https://we-calculate.com/calculator/mcg-to-mg-calculator.
TG we-Calculate Editorial Team, "mcg to mg Calculator — Micrograms to Milligrams," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/mcg-to-mg-calculator
@misc{wecalculate_mcg_to_mg_calculator, title = {mcg to mg Calculator — Micrograms to Milligrams}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/mcg-to-mg-calculator}}, year = {2026}, note = {TG we-Calculate} }
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