How many micrograms are in a milligram?

1 milligram is 1000 micrograms (µg, also written mcg), which is 1,000,000 nanograms. The mass units are exact powers of ten.

How do I work out a concentration?

Divide the mass by the solution volume. 5 mg in 2 mL is 2.5 mg/mL, which is 2500 µg/mL.

How do I convert mg to IU?

You need the substance's published potency in IU per mg. For recombinant human growth hormone (somatropin) the WHO reference is 3 IU per mg, so 1 mg is 3 IU and 1 IU is about 0.333 mg. Enter a different potency for another substance.

Do all peptides use IU?

No. Most research peptides are measured by mass (mg or µg). IU applies only to substances with a defined potency standard, such as somatropin. hCG is labelled in IU, but its mass-to-IU value depends on the preparation, so use the figure on the certificate.

Is this dosing guidance?

No. This is objective unit arithmetic on the numbers you enter, a laboratory reference, not medical or dosing guidance.

Unit Converter: mg, mcg, mL, IU

Peptide and hormone amounts turn up in several units: milligrams, micrograms, nanograms, a concentration in mg/mL, or international units (IU). This converter moves between them with objective arithmetic. Mass and concentration are exact; the IU conversion depends on a substance's published potency, which you set yourself.

Mass

Value

Unit

Gram (g): -
Microgram (µg): -
Nanogram (ng): -

Concentration

Mass dissolved in a volume of solution gives its concentration. This is the reagent concentration, the same figure the reconstitution calculator starts from.

Mass (mg)

Solution volume (mL)

Concentration (mg/mL): -
Concentration (µg/mL): -

Mass and IU

International units (IU) measure biological activity, not mass, so converting mass to IU needs the substance's published potency. Recombinant human growth hormone (somatropin) uses the WHO reference of 3 IU per mg. Change the potency below for a different substance.

Potency (IU per mg)

Default 3 IU/mg is the WHO reference for somatropin (recombinant hGH).

Mass (mg)

Activity (IU)

Activity (IU): -
Mass (mg): -
Mass (µg): -

Most research peptides are measured by mass (mg or µg), not IU. IU applies to substances with a defined potency standard. Human chorionic gonadotropin (hCG) is labelled in IU, but its mass-to-IU value depends on the specific preparation, so use the figure on your product's certificate rather than a fixed constant.

How the conversions work

Mass units

The mass units are exact powers of ten: 1 gram is 1000 milligrams, 1 milligram is 1000 micrograms (µg, also written mcg), and 1 microgram is 1000 nanograms. So 1 mg is 1000 µg is 1,000,000 ng.

Concentration

Concentration equals mass divided by volume. Dissolving 5 mg in 2 mL of bacteriostatic water gives 2.5 mg/mL, which is 2500 µg/mL. The concentration depends only on the total mass and the total volume, not on the size of any later aliquot.

International units

An IU is a unit of biological activity defined per substance, so it has no fixed mass equivalent across substances. For recombinant human growth hormone the WHO reference is 3 IU per mg, so 1 mg is 3 IU and 1 IU is about 0.333 mg (333 µg). A different substance uses a different constant, which is why the potency is an input here, not a fixed number.

This tool performs objective unit arithmetic on the numbers and potency you enter. It is a laboratory reference, not medical or dosing guidance.

Unit converter: frequently asked questions

Open source

This calculator is free and open source under the MIT license. Read the code, open an issue, or embed it on your own site.

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