Reconstitution calculator: concentration and mass per U-100 unit
This reconstitution calculator divides the vial amount in mg by the diluent volume in mL to give the concentration in mg/mL. It then expresses that concentration as the mass in one unit of a U-100 syringe, in mcg. You supply both numbers; the calculator has no target-amount field.
Arithmetic only, not medical advice. This describes the vial, not an injection: there is no target-amount field, and the calculator does not select either number or turn a target amount into a volume.
What do the fields mean?
Both fields start empty and nothing is filled in for you. The vial field is in milligrams; a vial labelled in mcg divides by 1,000 first (500 mcg is 0.5 mg).
| Field | What it is | Unit |
|---|---|---|
| Vial amount | The total amount in the vial, as printed on its label | mg |
| Diluent volume | The volume of diluent (for example, bacteriostatic water) in the vial after reconstitution | mL |
| Concentration | Vial amount divided by diluent volume | mg/mL |
| Per U-100 unit | The mass contained in one unit of a U-100 syringe at that concentration | mcg |
How is the result calculated?
Two steps. A U-100 syringe is scaled at 100 units per mL, so one unit is 0.01 mL, and 1 mg is 1,000 mcg.
- Concentration (mg/mL) = vial amount (mg) ÷ diluent volume (mL)
- Mass per U-100 unit (mcg) = concentration (mg/mL) × 0.01 mL × 1,000, which is the concentration × 10
Worked example
A vial labelled 10 mg holds 2 mL of diluent, so the concentration is 10 ÷ 2 = 5 mg/mL. One U-100 unit is 0.01 mL, so it contains 5 × 0.01 = 0.05 mg, which is 50 mcg.
The numbers are chosen to make the arithmetic easy to follow. They are not a suggestion for any product, diluent volume or amount.
What does the calculator deliberately leave out?
There is no target-amount field and no units-to-draw output. Both inputs start empty. The calculator does not select either number or turn a target amount into a volume.
MDCG 2019-11 Rev.1 says intended purpose governs whether software qualifies as medical device software. Software with a medical purpose that calculates or interprets medical information may qualify; arithmetic alone does not establish that purpose.[1]
Pinned's Terms state that it does not recommend compounds, sources, doses, or protocols. This page therefore stops after describing the entered vial and the U-100 scale.
How should you read the output?
Concentration is the entered vial amount divided by the entered diluent volume; changing either input changes the result. Per U-100 unit expresses that concentration as the mass in one unit of a U-100 syringe. It does not state a number of units to draw, because the page has no target-amount input.
The per-unit figure assumes U-100, which is 100 units per mL. On a U-40 syringe one unit is 0.025 mL, so the figure does not apply there. Nothing you type is saved or sent anywhere: the arithmetic runs in your browser, and refreshing the page clears it.
This calculator is an arithmetic tool, not medical advice. It does not recommend a compound, a dose or a diluent volume, and it cannot check whether any number you enter is right for you. Check every value against the product label and the instructions of your prescriber or pharmacist.
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