How Peptide Reconstitution Calculations Work
Reconstitution maths normalises every input to a single mass unit, divides mass by volume to get concentration, then divides the target amount by that concentration to get a volume that is finally scaled to syringe units.
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Step 1 — normalise units
Mixed units are the most common source of a wrong answer. Before anything else, every mass is converted to a single unit.
1 mg = 1000 mcg
1 mcg = 0.001 mg
Step 2 — concentration
Concentration expresses how much peptide sits in each millilitre of the reconstituted solution.
Concentration (mg/mL) = total vial amount (mg) ÷ diluent volume (mL)
Step 3 — dose volume and syringe units
Once concentration is known, the volume for any target amount is a single division, and the syringe reading is a linear scaling of that volume.
Dose volume (mL) = target amount (mg) ÷ concentration (mg/mL)
U-100 units = dose volume (mL) × 100
U-40 units = dose volume (mL) × 40
Step 4 — draws per vial
Dividing the total vial amount by the target amount gives how many equal draws the vial contains, before any residual volume left in the vial or needle is considered.
Draws per vial = total vial amount ÷ target amount per draw
Rounding and readable concentrations
Syringe barrels can only be read to a finite precision, so PepCalcs rounds displayed volumes and units to a practical number of decimal places. Where an optimisation is offered, it searches for a diluent volume that produces a round concentration such as 5, 10 or 20 mg/mL, because whole-number concentrations make each draw easier to read on the barrel. The optimisation only suggests a liquid volume — it never suggests what amount you should use.