Peptide Reconstitution Calculator

How to use this calculator

1. Enter the vial size in milligrams. This is printed on the vial label and on the certificate of analysis, e.g. 5 mg, 10 mg, or 20 mg.
2. Enter the bacteriostatic water volume in millilitres. Use the volume you actually intend to add, not the vial's total capacity.
3. Enter the dose and pick mcg or mg. Protocols for repair compounds are usually written in mcg; GLP-class compounds are usually written in mg. The toggle converts either way.
4. Select the syringe you are holding. U-100 is the default because it is by far the most common. U-40 syringes use a different graduation and will give a different unit number for the identical volume.
5. Read the results. The highlighted line gives the tick mark to draw to; the cards below show concentration, volume, and how many measurements the vial yields.

If the requested volume exceeds the syringe's capacity, the calculator says so. The fix is to add more bacteriostatic water (lowering concentration), or to use a larger syringe.

Worked examples

Example 1 — 5 mg vial, 2 mL water, 250 mcg measurement

Concentration is 5 mg ÷ 2 mL = 2.5 mg/mL, which is 2,500 mcg/mL. A 250 mcg measurement is 250 ÷ 2,500 = 0.10 mL. On a U-100 syringe, where 1 mL is 100 units, 0.10 mL is the 10 unit mark. The 5 mg vial yields 20 measurements of 250 mcg. This is the classic setup for BPC-157 and TB-500 research.

Example 2 — 10 mg vial, 2 mL water, 2.5 mg measurement

Concentration is 10 mg ÷ 2 mL = 5 mg/mL. A 2.5 mg measurement is 2.5 ÷ 5 = 0.50 mL, which is the 50 unit mark on a U-100 syringe and fills a U-50 syringe completely. The vial yields 4 measurements. Note how a larger unit dose consumes half the barrel: adding 4 mL instead of 2 mL would halve the concentration to 2.5 mg/mL and push the same 2.5 mg measurement to a full 1 mL — the entire syringe.

Example 3 — the same volume on a U-40 syringe

Take the 0.10 mL from Example 1 and switch to a U-40 syringe. U-40 barrels are graduated at 40 units per mL, so 0.10 mL is 4 units, not 10. The liquid volume is identical; only the printed scale differs. Mixing up the two scales is a 2.5× error, which is why the syringe selector matters as much as the numbers.

Understanding insulin syringe units

Insulin syringes are not marked in millilitres — they are marked in "units", a scale originally defined for insulin concentration. On a U-100 syringe, 100 units = 1 mL, so a single unit is 0.01 mL. A U-50 syringe uses the same 100-units-per-mL scale but holds only half a millilitre, giving 50 units of travel across a longer barrel — the tick marks are further apart and therefore easier to read for small measurements. A U-40 syringe is 40 units = 1 mL, so each unit is 0.025 mL.

Because the unit is a volume, not a mass, the same "10 units" means completely different amounts of peptide at different concentrations. Ten units of a 2,500 mcg/mL solution is 250 mcg; ten units of a 10,000 mcg/mL solution is 1,000 mcg. Never carry a unit number over from one reconstitution to another — recalculate whenever the vial size or the water volume changes. The calculator always shows the volume in millilitres alongside the unit figure so the two can be cross-checked.

Practical handling notes

Add the diluent slowly against the inside wall of the vial rather than directly onto the powder cake, then let it dissolve on its own or swirl gently. Peptides are long chains that can be damaged by aggressive shaking. Once in solution, store the vial refrigerated and away from light, and label it with the date and the concentration you calculated — the concentration is the one number you cannot recover later by looking at the vial.

Every batch we supply ships with a certificate of analysis so the stated mass on the label can be verified before any calculation is made. See our COA, ADS and MSDS library, the how to mix peptides guide, or browse the peptide encyclopedia for compound-specific reference material.