1 mg = 1,000 mcg. Conversion tables for the amounts searched most, what a vial labelled in mg holds in mcg, and the mcg-per-mL step that decides units.
A peptide vial is labelled in milligrams; the amounts reported in trials, labels and forum posts are usually in micrograms. Converting one into the other is a single step, a factor of 1,000, and it is the step where a decimal point goes missing. This page gives the conversion, tables for the amounts people search for, what each common vial holds in micrograms, and how the conversion carries into a concentration.
Turning a milligram amount into syringe units at a given concentration is the job of the mg to units page; the syringe scales themselves are on the insulin syringe units page. This page stays with the conversion between the two mass units.
The conversion
The metric prefixes step in powers of ten: milli is 10⁻³ and micro is 10⁻⁶ (NIST, Guide to the SI, prefix table). A milligram is therefore 1,000 micrograms.
- mg → mcg: multiply by 1,000, or move the decimal point three places to the right. 0.25 mg → 250 mcg.
- mcg → mg: divide by 1,000, or move it three places to the left. 750 mcg → 0.75 mg.
"mcg" and "µg" are the same unit. The Greek µ is the SI symbol; "mcg" is the spelling used on many labels and in pharmacy practice because a handwritten µ can be read as an "m".
Micrograms to milligrams: the searched amounts
| Micrograms |
Milligrams |
| 10 mcg |
0.01 mg |
| 50 mcg |
0.05 mg |
| 100 mcg |
0.1 mg |
| 200 mcg |
0.2 mg |
| 250 mcg |
0.25 mg |
| 300 mcg |
0.3 mg |
| 500 mcg |
0.5 mg |
| 750 mcg |
0.75 mg |
| 1,000 mcg |
1 mg |
| 2,500 mcg |
2.5 mg |
| 5,000 mcg |
5 mg |
Milligrams to micrograms
| Milligrams |
Micrograms |
| 0.05 mg |
50 mcg |
| 0.1 mg |
100 mcg |
| 0.25 mg |
250 mcg |
| 0.5 mg |
500 mcg |
| 1 mg |
1,000 mcg |
| 2 mg |
2,000 mcg |
| 2.5 mg |
2,500 mcg |
| 5 mg |
5,000 mcg |
| 10 mg |
10,000 mcg |
What a vial holds, in micrograms
This site's calculator data lists vial sizes for 52 compounds. Written in micrograms, the range is wide:
| Vial on the label |
Contents in mcg |
Example compounds in the data |
| 0.1 mg |
100 mcg |
IGF-1 LR3 (small vial) |
| 1 mg |
1,000 mcg |
Follistatin 344, IGF-1 LR3 |
| 2 mg |
2,000 mcg |
HGH Fragment 176-191, AOD-9604, oxytocin, gonadorelin, MGF |
| 5 mg |
5,000 mcg |
BPC-157, TB-500, ipamorelin with CJC-1295, most of the list |
| 10 mg |
10,000 mcg |
BPC-157, cagrilintide, the 10 mg sizes of most compounds |
| 50 mg |
50,000 mcg |
GHK-Cu, 5-Amino-1MQ, epithalon and SS-31 (large vials) |
| 2,000 mg |
2,000,000 mcg |
Glutathione (largest size) |
From the smallest vial to the largest is a factor of 20,000. Of the 52 compounds, 42 are listed only in vials between 1 and 20 mg. GHK-Cu, 5-Amino-1MQ, NAD+ and glutathione come in tens to thousands of milligrams; tirzepatide, Semax, NA-Semax-Amidate, epithalon and SS-31 add a 30 or 50 mg size; IGF-1 LR3's smallest vial is a tenth of a milligram. Reusing a figure from one compound's page on another's vial is where these sizes matter.
From mass to concentration
Once water is added, the question becomes how many micrograms are in each millilitre:
mcg/mL = vial mg × 1,000 ÷ mL of water
| Vial |
Water |
mg/mL |
mcg/mL |
mcg per unit (U-100) |
| 2 mg |
1 mL |
2 |
2,000 |
20 |
| 2 mg |
2 mL |
1 |
1,000 |
10 |
| 5 mg |
1 mL |
5 |
5,000 |
50 |
| 5 mg |
2 mL |
2.5 |
2,500 |
25 |
| 5 mg |
2.5 mL |
2 |
2,000 |
20 |
| 10 mg |
1 mL |
10 |
10,000 |
100 |
| 10 mg |
2 mL |
5 |
5,000 |
50 |
| 10 mg |
3 mL |
3.33 |
3,333 |
33.3 |
A U-100 syringe marks 100 units per millilitre, so one unit is 0.01 mL and holds one hundredth of the mcg/mL figure. The reconstitution calculator does the same arithmetic for any vial and volume, and each compound's reconstitution page works its common vial sizes.
Where the factor of 1,000 goes wrong
- The unit is dropped. "250" or "0.25" written without a unit can be read in either. A figure is only usable with its unit.
- The concentration is left in mg/mL while the amount is in mcg. 250 ÷ 2.5 = 100 looks like 100 units; the correct figure is 250 mcg ÷ 2,500 mcg/mL = 0.1 mL, or 10 units. Converting both to the same unit first removes this error.
- µ is read as m. Handwritten or low-resolution, "µg" can pass for "mg". PubMed indexes a neonatal death under the title "A fatal zinc overdose in a neonate: confusion of micrograms with milligrams" (P&T 2011). The same factor of 1,000 separates the two readings of any peptide figure.
- IU is treated as a mass. An international unit measures biological activity, not weight. There is no general IU-to-mg factor; where one exists it belongs to that product and is stated by its maker.
What this page does not do
It converts units. It does not say what amount of anything to use; the dose pages report what labels, trials and vendor pages state, each with a source and a date, starting from the peptide dosage chart.
Sources and dates
Opened 2026-09-26: NIST Special Publication 811, Guide for the Use of the International System of Units, chapter 4 (SI prefixes); the PubMed record for Grissinger, P&T 2011;36(7), PMID 21931469 (title only — the publisher does not release the full text to PubMed Central); vial sizes from this site's calculator data (compound-data, 52 compounds, counted 2026-09-26). All conversions and concentrations are arithmetic by this site. Corrections go to the contact page.
