How the math works

Concentration is vial mass divided by the volume of water added. Syringe units follow from the concentration and the amount the reader chooses. The calculators show the formula beside the result so every number can be checked by hand.

Dosage references report figures as stated by their sources: product labels, trial protocols, formularies and reviews, each linked and dated. A figure without a source is not published.

The site never uses the second person or the imperative about a dose. It reports; it does not recommend. Every page carries the research-use disclaimer.

The three formulas

1. 1. Concentration

   vial amount (mg) ÷ water volume (mL) = mg/mL

   A 5 mg vial with 2 mL of bacteriostatic water is 2.5 mg/mL.

2. 2. Volume

   amount wanted ÷ concentration = mL

   250 mcg (0.25 mg) at 2.5 mg/mL is 0.1 mL.

3. 3. Syringe units

   volume (mL) × 100 = units on a U-100 syringe

   0.1 mL is 10 units. One unit is 0.01 mL, whatever the vial contains.

The one external constant is the U-100 scale: standard insulin contains 100 units in 1 mL, and each small notch on a standard 1 mL insulin syringe is one unit — MedlinePlus (NIH/NLM), Giving an insulin injection. Milligrams to micrograms is a factor of 1,000. Nothing else goes into the arithmetic.

The rules every page is held to

1. 01Report, never recommend. Calculators output concentration and syringe units from what the reader enters. No preset is a suggested amount, and no page uses the second person or the imperative about a dose.
2. 02A figure carries its source. Dosage references state what a label, a trial protocol or a formulary states, with the document and the date. A figure without a source is not published.
3. 03Facts are shared, sentences are not. The five locale versions of a page carry the English page's verified figures; each language writes its own sentences rather than a translation of the English ones.
4. 04The disclaimer is on every page that needs it. Every calculator, stacking and dosage page carries the research-use notice; articles that report dosages carry the liability notice top and bottom.
5. 05Nothing is sold here. Product cards link to medibact.com and carry no offer markup. The site earns nothing from any other seller and links to none.

Last updated: 2026-09. Material updates to this page are dated. Where a page has a gap, it says so rather than filling it; corrections go through the contact page.