Reconstitution Calculator Math: How Water Volume Changes Concentration
Reconstitution math starts from two figures: the amount in the vial and the volume of water entered. Dividing one by the other gives the concentration. Every later figure, the draw volume in mL and the reading in syringe units, is computed from that concentration.
The Peptide Reconstitution Calculator runs these steps. For an overview of all three figures, see reconstitution basics.
The chain
- Concentration: the vial amount divided by the water volume, in mg per mL.
- Draw volume: the amount entered divided by the concentration, in mL.
- Syringe units: the draw volume multiplied by the scale's units per mL.
Worked example: one vial, three water volumes
These are illustrative round numbers, not amounts for any product.
Inputs: a vial of 10 mg, an amount of 1 mg, and a U-100 scale. Only the water volume changes between the three runs.
- 10 mg ÷ 1 mL computes to 10 mg/mL. An amount of 1 mg ÷ 10 mg/mL computes to 0.1 mL, which is 10 units on a U-100 scale.
- 10 mg ÷ 2 mL computes to 5 mg/mL. An amount of 1 mg ÷ 5 mg/mL computes to 0.2 mL, which is 20 units on a U-100 scale.
- 10 mg ÷ 4 mL computes to 2.5 mg/mL. An amount of 1 mg ÷ 2.5 mg/mL computes to 0.4 mL, which is 40 units on a U-100 scale.
Reading the pattern
The three runs differ only in the water volume. Doubling the water halves the concentration, which doubles the draw volume and the unit reading for the same amount. The total in the vial never changes. Each run is equally valid arithmetic on its own inputs; the calculator computes whichever water volume is entered and does not compare one against another.