Peptide Vial Math

IU calculator for HGH and hCG

Syringe units = amount IU ÷ (vial IU ÷ water mL) × 100. A 10 IU vial with 1 mL of water is 10 IU/mL, so 2 IU is 0.2 mL, or 20 units on a U-100 syringe.

For somatropin (HGH), 1 mg = 3 IU by the WHO standard. Use your own label's numbers.

By Peptide Vial Math Editorial Team Reviewed by the team on (how we review) Updated Formulas unit-tested (methodology)

  IU calculator

IU or USP Units

Concentration
10 IU/mL
Draw volume
0.2 mL
Syringe reading
20 units

2 IU ÷ 10 IU/mL = 0.2 mL × 100 = 20 units

If the vial is somatropin (HGH): 0.667 mg in the draw, and the vial holds 3.33 mg (3 IU = 1 mg).

Arithmetic only. An IU is a unit of biological activity; a syringe unit is a volume mark. They are not the same thing.

Why are there two kinds of “unit”?

HGH and hCG vials are labeled in international units (IU) or USP Units: a measure of biological activity fixed against a reference standard. Insulin syringes are printed in “units” too, but those are volume marks: on a U-100 barrel, 1 unit = 0.01 mL. The two only line up after you choose how much water to add. Put 10 IU into 1 mL and each syringe unit holds 0.1 IU; put the same vial into 2 mL and each syringe unit holds 0.05 IU.

IU/mL = vial IU ÷ water mL
draw volume (mL) = amount IU ÷ IU/mL
U-100 units = mL × 100

How many IU are in 1 mg of HGH?

Three. When WHO established the second International Standard for somatropin (recombinant human growth hormone), it defined the specific activity as 3.0 IU per mg. That fixed factor is why HGH can be converted between IU and mg: divide IU by 3 for mg, multiply mg by 3 for IU.

Somatropin (HGH): IU → mg → mcg at 3 IU per mg
IUmgmcg
1 IU0.333333
2 IU0.667667
3 IU11,000
4 IU1.331,333
5 IU1.671,667
6 IU22,000
8 IU2.672,667
10 IU3.333,333
12 IU44,000
15 IU55,000
20 IU6.676,667
30 IU1010,000
Somatropin (HGH): mg → IU
mgIU
0.5 mg1.5
1 mg3
1.5 mg4.5
2 mg6
3 mg9
3.33 mg9.99
5 mg15
10 mg30

How many IU does each syringe unit hold?

IU per U-100 syringe unit for reference vial contents (rows) and water volumes (columns). Rows are evenly spaced arithmetic, not common vial sizes or suggested amounts. Multiply the cell by the units you draw to get IU.

IU per U-100 unit = (vial IU ÷ water mL) ÷ 100
Vial0.5 mL1 mL2 mL3 mL
10 IU0.20.10.050.0333
15 IU0.30.150.0750.05
20 IU0.40.20.10.0667
30 IU0.60.30.150.1

If you have a prescription somatropin pen or cartridge, it comes with its own labeled strength and instructions; follow the label and your prescriber, not this table.

How do you reconstitute an hCG vial?

The Novarel label lists multiple-dose vials of 5,000 or 10,000 USP Units of chorionic gonadotropin, each packed with a 10 mL vial of Bacteriostatic Water for Injection (0.9% benzyl alcohol). It says the reconstituted solution should be refrigerated and used within 30 days, and that the product is for intramuscular use. hCG is labeled in units of activity with no fixed mg factor, so the arithmetic stays in units.

hCG: units per mL and per U-100 syringe unit, by water added
Vial1 mL2 mL5 mL10 mL
5,0005,000/mL
50 per unit		2,500/mL
25 per unit		1,000/mL
10 per unit		500/mL
5 per unit
10,00010,000/mL
100 per unit		5,000/mL
50 per unit		2,000/mL
20 per unit		1,000/mL
10 per unit

Worked example: a 10,000-unit vial with the 10 mL supplied is 1,000 units per mL. Measuring 250 units takes 0.25 mL, which reads 25 on a U-100 syringe. The same amount from a 5,000-unit vial with 10 mL takes 50 units, twice as many, because the solution is half as strong.

Frequently asked questions

How many IU of HGH are in 1 mg?

3 IU. The WHO International Standard for somatropin (recombinant human growth hormone) defines its specific activity as 3.0 IU per mg, so 1 mg = 3 IU and 10 IU = 3.33 mg.

How do I convert IU to syringe units?

Divide the vial IU by the water in mL to get IU per mL. Divide the amount in IU by that to get mL, then multiply by 100 for a U-100 syringe. 10 IU in 1 mL is 10 IU/mL, so 2 IU = 0.2 mL = 20 units.

Is an IU the same as a unit on an insulin syringe?

No. An IU (or USP Unit) measures biological activity. A syringe unit is a volume mark: 0.01 mL on a U-100 barrel. How many IU each syringe unit holds depends entirely on how much water went into the vial.

How do I calculate units for a 10,000 IU hCG vial?

With the 10 mL of bacteriostatic water the Novarel label supplies, the vial is 1,000 IU per mL, so each U-100 syringe unit holds 10 IU. 250 IU = 0.25 mL = 25 units. With 5 mL it is 2,000 IU/mL and 20 IU per unit.

Can hCG IU be converted to mg?

Not with a single fixed factor the way HGH can. hCG is labeled and measured in units of activity, so do the arithmetic in units: vial units ÷ water mL, then amount ÷ that concentration.

Converters and guides

Sources

  1. The Second International Standard for somatropin (recombinant DNA-derived human growth hormone): preparation and calibration in an international collaborative study — Bristow AF, Jespersen AM. Biologicals 29(2):97–106, 2001, PMID 11580214
  2. Novarel (chorionic gonadotropin for injection, USP): prescribing label — DailyMed, U.S. National Library of Medicine (Ferring Pharmaceuticals), 2025
  3. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products — U.S. Food and Drug Administration, 2024
  4. Bacteriostatic Water for Injection, USP (Hospira) — prescribing label — DailyMed, U.S. National Library of Medicine

Links checked 2026-10-19.