Why this site exists

What it does

One calculator: give it a vial amount, a water volume, and a dose, and it shows the exact mark to draw to on a U-100 insulin syringe. Alongside the number it draws the vial and the syringe, compares what different water volumes do to your draw, works out cost per dose, warns when a draw is too small to measure accurately, and catches the 1000x slip between milligrams and micrograms before it bites.

There is also a private vial tracker. Save a vial and it keeps the strength, the units per draw, and how many doses are left, logs each draw with its date, and counts down to the discard date, with a one-tap calendar reminder. It lives in your browser only: no account, and nothing is sent anywhere. The calculator page also explains how to read a U-100 syringe, with an interactive barrel, and a short guide covers the mixing process itself.

Every result is shown before anything is asked of you. There is no account, no sign-up wall, and no step where the answer is withheld until you hand over an email address. The email boxes are the only asks, they are optional, and every result appears before any of them.

What it deliberately doesn’t do

• It sells nothing, and links to no store.
• It names no specific compound, and does not host a database of them. The arithmetic is identical whatever is in the vial, which is precisely why it can be written once and be correct.
• It gives no dosing advice. What to take, whether to take it, and how much is a conversation with a licensed medical provider, not a calculator.
• It makes no claims about outcomes, benefits, or safety.

That list isn’t modesty. A measurement tool that stays a measurement tool is one you can actually check, and checkable is the only kind of useful worth being.

How the figures are checked

The arithmetic is deliberately visible: every result on the calculator has a “show the math” toggle that prints the three steps with your own numbers substituted in, so you can verify it by hand rather than trust it. Concentration is the vial amount divided by the water volume; volume is the dose divided by that concentration; units are that volume times one hundred, because a U-100 syringe is graduated at a hundred units to the millilitre.

Where a guide states a figure that isn’t arithmetic, such as the preservative concentration in bacteriostatic water, the 28-day window, or refrigeration ranges, it cites a primary source, and those citations are listed at the foot of each guide. If you find something wrong, please tell us and include the figure; corrections get made and dated.

The email list

One list, used for one thing: a short note when a measurement guide is added or updated. That is all it is for. It is never sold or rented, every message has an unsubscribe link, and the privacy policy says plainly what is stored and how to have it deleted.