Mass, volume and concentration are different quantities
A vial may state a nominal amount in mg (milligrams). One mg equals 1,000 mcg (micrograms). A liquid volume in mL is not itself a mass. The concentration is the verified mass divided by the independently confirmed final volume: mg/mL. An amount in mcg divided by concentration in mcg/mL yields liquid volume in mL.
What does a U-100 marking mean?
A U-100 syringe scale is calibrated so 100 markings represent 1 mL of volume and one marking is 0.01 mL. That number does not represent an International Unit (IU) of biological activity for an arbitrary peptide. HCG and other IU-labelled medicines are not convertible to mg using this simple concentration formula.
Worked arithmetic example—not a preparation instruction
If, and only if, a validated formulation documented 10 mg of compound in 2 mL final solution, the arithmetic concentration would be 5 mg/mL or 5,000 mcg/mL. A hypothetical 0.01 mL of that solution would contain 50 mcg. These values do not establish that 2 mL of any diluent is compatible with a supplier's vial or that any dose is appropriate.
What the calculator does and does not check
Enter labelled mass, verified final volume and an amount to evaluate; press Apply to update the calculator. It can detect zero and overflow inputs, but it cannot check identity, assay, sterility, prescription, route, clinical dose, diluent compatibility or stability. If inputs are unknown, do not substitute internet defaults.
Common unit mistakes
Check mg versus mcg (a thousand-fold difference), final volume versus the volume initially added, U-100 markings versus IU of activity, and a commercial pen's labelled dose versus a research vial's nominal content. If a calculation exceeds device capacity or seems too small to measure accurately, stop and have the verified formulation and arithmetic reviewed by a qualified professional.