Free tool · no signup
Reconstitution calculator
Enter a vial size, the water you added, and a target dose. Get concentration and draw volume back — in mL and in U-100 insulin-syringe units. Nothing to install, no account, no compound list to pick from.
Enter your numbers
Result
Results appear when every box holds a number.
Correct until something changes. Reconstitute at a different volume, switch vial size, or adjust the dose and all three of these move — that is what the tracker keeps straight for you.
Want the whole protocol tracked?
This calculator does one thing. VialMath, the app, does the rest — cycles and phases, vial burn-rate and reorder timing, a decision log for gate checks, and retroactive logging for the day you forget. Same math you just used, applied to a full protocol.
- Free to use. Power is $39 once — no subscription, ever. It adds more than two tracked compounds, multiple doses per day, cycle windows, vial inventory, applying a scenario as a dated dose change, Data check and Dose log export.
- No account. Runs on your device.
The questions people actually ask
How does vial concentration affect the calculation?
Concentration is vial size divided by diluent volume — both numbers you choose and enter. It is the only thing that turns a dose into a number of units on the barrel: the same dose at half the concentration is twice the volume. Change either number and the draw changes with it.
How many units do I draw?
Units come from three things you already know: the vial size, the water you added, and the dose you intend to take. Enter those three and the calculator returns the units. It does not choose any of the three for you — they are yours to enter, and it only does the maths on what you type.
How many milligrams is that?
The calculator works in one direction: from a dose you enter, in mg or mcg, to the volume to draw, in mL and in U-100 insulin-syringe units. It does not convert a number of units into a dose.
What is a "unit" on an insulin syringe?
On a U-100 syringe, 100 units is 1 mL — so one unit is one hundredth of a millilitre. That is a fixed definition of the syringe, not a dose.
Do I have to redo this every time I open a new vial?
Not in the full app. You can save a mix under your own name and reuse it, so a refill is one tap instead of re-entering the same numbers every few days.
More free tools
One question each. No signup, nothing to install.
Told when it changes
New free tools and app updates. Nothing else, and rarely — there is no newsletter here.
Your address, the page you signed up on, and the date — nothing else is kept with it. Never sold, never shared, never passed to anyone selling anything. One click unsubscribes. Your protocol data is separate and stays on your device — the app has no account and sends us nothing.