Peptide reconstitution, without the guesswork.

Many research peptides ship as a freeze-dried powder because they are more stable dry. Reconstitution is simply dissolving that powder in a sterile liquid so the amount inside can be measured by volume. Nothing about the compound changes. You are converting a mass you cannot draw into a concentration you can.

The vial label tells you the mass inside, usually in milligrams. The liquid you add sets how concentrated the finished solution is. Add more liquid and each unit on the syringe holds less peptide. Add less and each unit holds more. That single relationship is the whole game.

Three units of measure show up constantly, and mixing them up is where most confusion starts.

• mg (milligram)

  A unit of mass. Vial strengths are almost always printed in mg (for example a 5 mg vial). One milligram is one thousand micrograms.

• mcg (microgram)

  A smaller unit of mass, one thousandth of a milligram. Many peptides are measured in mcg, so 1,000 mcg equals 1 mg. The calculator converts between the two for you.

• units (on an insulin syringe)

  A volume marking, not a mass. On a standard U-100 insulin syringe, 100 units equal 1 mL, so one unit is 0.01 mL. Units tell you how far to draw the plunger, once the concentration is known.

• IU (international unit)

  A measure of biological activity used for some hormones, not for peptides sold by mass. It is a different scale from the volume units printed on a syringe, and the two are not interchangeable.

The liquid added to a vial is a diluent. Bacteriostatic water (often shortened to BAC water) is sterile water containing a small amount of benzyl alcohol, which limits microbial growth so a multi-use vial stays usable longer. Sterile water and saline are other diluents that appear in the literature. Which diluent is appropriate depends on the specific compound and its handling notes, and is a question for a qualified professional, not a calculator.

The volume of diluent you choose is what sets your concentration. That is why the same vial can read as two different numbers of units depending only on how much water went in.

Because units on a syringe are a measure of volume, the number you draw to is only meaningful once you know the concentration. Two people can hold the same vial, add different amounts of water, and end up drawing to completely different marks for the same intended amount. Getting the arithmetic right is what keeps the mark on the syringe consistent with the amount you meant to measure.

The calculator above does exactly this arithmetic and nothing more. It does not know your compound, it does not suggest an amount, and it is not a schedule. It converts the numbers you type into a concentration and a syringe mark.