Every reconstitution comes down to the same small piece of arithmetic, and getting it wrong by a decimal place is the most common lab error there is. The PlusPeps peptide calculator does the sums for you. This guide explains what it is doing, so you can check its answer against your own head.
The three numbers
Peptide in the vial, in milligrams (mg). It is on the label: 5 mg, 10 mg, and so on.
Water added, in millilitres (mL). You choose this. More water means a weaker solution and larger, easier-to-measure volumes. Less water means a stronger solution and smaller volumes. Most vials comfortably take 1 to 3 mL.
Syringe units. A standard 1 mL insulin-type syringe is marked in 100 units. So 1 unit is 0.01 mL, 10 units is 0.1 mL, 50 units is 0.5 mL.
The one formula
Concentration = peptide (mg) ÷ water (mL). That gives milligrams per millilitre. Multiply by 1,000 to get micrograms (mcg) per millilitre, then divide by 100 to get micrograms per syringe unit.
Example: a 5 mg vial reconstituted with 2 mL of water.
- 5 mg ÷ 2 mL = 2.5 mg per mL
- 2.5 mg per mL = 2,500 mcg per mL
- 2,500 mcg ÷ 100 units = 25 mcg per unit
So 10 units of that solution contain 250 mcg, 20 units contain 500 mcg, and the full 100-unit syringe contains 2.5 mg.
Working backwards from a target amount
If your protocol calls for a specific amount per measurement, you can pick the water volume so that the amount lands on an easy-to-read line. Divide the target amount by the concentration to get the volume. With the 25 mcg-per-unit solution above, a 250 mcg measurement is 10 units: a round number, easy to see, hard to misread. Changing the water volume changes which amounts land on round numbers, which is the main reason to think before you add water. The calculator lets you try different volumes and see the units update.
Mistakes the calculator cannot catch
- Reading the wrong vial strength. A 10 mg vial dissolved as if it were 5 mg gives double the concentration you think you have.
- Mixing up mL and units. 1 mL is 100 units, not 1 unit.
- Adding water twice. Decide the volume, add it once, write it on the label.
- Trusting the label’s milligrams as pure peptide. Net peptide content is usually lower; see what 99% purity means.
Write it down
The moment the vial is reconstituted, label it with the product, the concentration in mcg per unit, and the date. Future you, reaching into the fridge a week later, will be grateful.
The calculator and this guide are measuring aids for laboratory work. They are not dosing recommendations, and nothing on this site is medical advice. All products are sold for research use only.
