Concentration Calculator
Everything else -- dose volume, syringe units -- starts from this one number.
Try the calculator, free →The starting point for every dose calculation
Concentration is how much medication is in each mL of your reconstituted vial, and it's the number every later step depends on. It only takes the amount originally in the vial and how much diluent you added:
concentration (mg/mL) = vial amount (mg) ÷ diluent volume (mL)
Worked example
A 10 mg vial reconstituted with 5 mL of bacteriostatic water:
10 mg ÷ 5 mL = 2 mg/mL
Every mL you draw from that vial now contains 2 mg -- so a 1 mg dose means drawing 0.5 mL, a 4 mg dose means drawing 2 mL, and so on.
More diluent means a lower concentration
The same 10 mg vial reconstituted with 10 mL instead of 5 mL would give a concentration of 1 mg/mL -- half as strong, meaning you'd need to draw twice the volume for the same dose. This is exactly why the diluent volume you actually added (not just what the label suggests) matters for every calculation that follows.