Vial + water + dose → units.
Pick the compound, the vial you have, how much water you're adding, and the dose you're drawing. The answer is the number on your syringe — with the chart to print and the vial size to buy.
What this does, in one sentence
It turns three numbers you already know — the milligrams printed on the vial, the millilitres of bacteriostatic water you add, and the dose you want — into the one number you actually need: where to draw to on an insulin syringe.
Why a calculator and not a chart
Charts assume a vial size and a water volume. The moment yours are different, the chart is wrong and you're doing long division at the kitchen counter. This does the division, tells you if the answer lands between tick marks, and tells you what to change if the dose is too small to measure well. Then it prints the chart for your setup.
The three things it will flag
- Too few units to measure. Under about 5 units on a U-100 syringe the reading error gets big. The fix is more water, not a steadier hand — and it tells you exactly how much.
- More units than the syringe holds. A 0.3 mL syringe stops at 30 units. Add less water or use a bigger syringe.
- Between tick marks. A 1 mL syringe reads in 2-unit steps; a 0.5 mL in 1-unit steps; a 0.3 mL in half-units. If your number lands between marks, it names the nearest marks and the syringe that reads it exactly.
Questions people actually type
How many units is 1 mg?
It depends entirely on the concentration. 1 mg from a 10 mg vial reconstituted with 2 mL of water (5 mg/mL) is 0.2 mL = 20 units. The same 1 mg from a 5 mg vial in 1 mL (also 5 mg/mL) is also 20 units. From a 10 mg vial in 1 mL (10 mg/mL) it is 10 units. Set your vial and water above and the chart shows every common dose.
What is a unit on an insulin syringe?
A unit on a U-100 insulin syringe is 0.01 mL of volume. 100 units = 1 mL. Units measure volume, not the amount of compound — that is why the same dose is a different number of units at a different concentration.
Does this work offline?
Yes. Once it has loaded over HTTPS, the service worker caches the app so the calculator runs with no signal. Add it to your home screen and it opens like an app.
Is this medical advice?
No. It is arithmetic. It does not recommend any compound, dose, or use. The quick-fill amounts are numbers people commonly search for, not suggestions. Use the protocol you were given and confirm with the person who gave it to you.
Where do you get vials?
We order from ZestyRat Research — batch-specific COAs, sealed vials, tracked US shipping and a clean record across every order placed through our sites. Code SHAUN10 takes 10% off. They are not a clinic and nobody there reviews your labs; the page on where we buy says so plainly.