Isometric reference grid with placeholder rows and unit-type icons for weight, volume, and measuring cylinder, representing a units primer

mcg, mg, and Molarity: A Units Primer for the Lab

Key takeaways

1,000 micrograms (mcg) = 1 milligram (mg); divide mcg by 1,000 to get mg.
1 milliliter (mL) = 1,000 microliters; 0.1 mL = 100 microliters.
Concentration is mass-per-volume (mg/mL) or molarity (µM, nM via molecular weight).
All framing is laboratory units, in vitro only.

Peptide work uses a small set of units: micrograms and milligrams for mass, milliliters and microliters for volume, and molarity for assays. This primer defines each.

Mass: micrograms and milligrams

1,000 micrograms (mcg) = 1 milligram (mg). So 100 mcg = 0.1 mg and 500 mcg = 0.5 mg. To go from mcg to mg, divide by 1,000; to go from mg to mcg, multiply by 1,000.

Volume: milliliters and microliters

1 milliliter (mL) = 1,000 microliters (µL). So 0.1 mL = 100 µL. Volumes in the lab are often measured in microliters for small amounts.

Concentration: mg/mL and molarity

Mass-per-volume (mg/mL) is milligrams of peptide per milliliter of solution. Molarity (micromolar µM, nanomolar nM) expresses molecules per volume and uses the peptide's molecular weight to convert from mg/mL.

Quick reference table

Volume (mL)	Microliters (µL)
0.1 mL	100 µL
0.3 mL	300 µL
0.5 mL	500 µL
1 mL	1,000 µL

Related research guides

Research-use note

This describes laboratory units for in vitro research use only.

Related research: LIPO-C | MIC-C.

Frequently asked questions

How many micrograms are in a milligram?

1,000 micrograms (mcg) = 1 milligram (mg); divide mcg by 1,000 to convert to mg.

How do milliliters and microliters relate?

1 milliliter (mL) = 1,000 microliters (µL), so 0.1 mL = 100 µL.

What is molarity?

Molecules per volume (micromolar µM, nanomolar nM), converted from mg/mL using the peptide's molecular weight.

Research use only?

Yes, in vitro laboratory research use only.