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Enter a vial size, a dose, and how often you dose. Get doses per vial and days per vial back — plus concentration and draw volume if you add the diluent you used. Nothing to install, no account, no compound list to pick from.
Only needed to also show concentration and draw volume below — doses and days per vial don't depend on it.
Blend? Enter the vial size and the dose the same way: both for one component, or both as totals.
Whole days. 1 for daily, 7 for weekly, and so on.
Count from the first dose, not the day before it. For example, 20 doses taken every 3 days span 19 intervals: the last dose falls 57 days after the first. If your dose doesn't divide the vial evenly, the result is instead the day of the first dose the vial can't fully cover — the day you need a new vial.
Doses per vial is the vial size divided by your dose — full doses only, the same way the rest of VialMath counts what's left in a vial. It doesn't need the diluent amount: concentration changes how much liquid you draw per dose, never how many doses fit in the vial. Days per vial walks the calendar forward one day at a time from a fresh vial, at the frequency you entered, and reports the day of the dose that empties the vial: the last full dose when your dose divides the vial evenly, otherwise the first dose the vial can't fully cover, which is the day you need a new vial — the exact engine the Run-Out Date calculator uses, so the two never disagree on the same numbers. Concentration and draw per dose are the same reconstitution math as the calculator: vial size ÷ diluent = concentration, and dose ÷ concentration × 100 = units on a U-100 syringe.
A vial holds 10 mg. You added 2 mL of diluent and your dose is 0.5 mg, taken every 3 days. Concentration: 10 mg ÷ 2 mL = 5 mg/mL. Draw per dose: 0.5 mg ÷ 5 mg/mL × 100 = 10 units (0.1 mL). Doses per vial: 10 mg ÷ 0.5 mg = 20. Days per vial: dosed every 3 days from a fresh vial, the 20th dose falls 3 × 19 days after the first — 57 days of supply. Every number above is checkable on a calculator.
VialMath keeps your calculations, schedule, inventory and history connected.
More free tools: the reconstitution calculator, when does a vial run out?, and the full list →
Divide the vial size by your dose to get full doses per vial. Multiply that against how often you dose to get roughly how many days a fresh vial covers — the calculator above does the exact version of that walk, day by day, so it handles the leftover-amount edge cases correctly.
Vial size divided by dose size, rounded down to full doses — a vial with a little left over after the last full dose still only counts as that many complete doses, never a fractional extra one.
No. The diluent sets the concentration, which changes how many mL or units you draw per dose — not how many milligrams are in the vial. A vial's total mg content, and so its doses per vial, is fixed the moment it's made, however much or little water goes in.
The calculator counts full doses only. A partial amount left in the vial after the last full dose is not counted as an extra dose — it's leftover, not supply.
Not in the full app. Save a mix and a schedule once, and the next vial's burn rate and run-out date are already there when you open a fresh one.
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