Tirzepatide Dose Calculator: Convert mg to Syringe Units and mL

1. Choose what is in your hand: a compounded vial, a Zepbound or Mounjaro vial, or a pen. Pens and branded vials need no conversion, and the calculator says why.
2. Type the strength the way your vial label prints it, such as 20 mg/mL or 10 mg / 0.5 mL, and your prescribed dose in mg. The calculator repeats back how it read the label.
3. Read the line to draw to on your syringe size, the mg that line holds, and your dose ladder at this vial’s strength. A dose above the 15 mg label maximum is shown next to the step a tenth its size; a dose below 2.5 mg is shown as it is, with its units.
4. Add the mL of liquid in the vial and the date of your first draw to see how many doses the vial gives before FDA’s 28-day discard date, or the date on your label if it is earlier, then copy the link, save the card as an image, print it or add the shot dates to your calendar.

On a U-100 insulin syringe, 100 units fill 1 mL. FDA describes a 5-unit dose on a 1 mL U-100 syringe as 0.05 mL (FDA alert on compounded semaglutide dosing errors), so each unit mark is 0.01 mL whatever the vial holds. The concentration on the label decides how many mg are in that volume.

Units = dose in mg ÷ concentration in mg/mL × 100. Volume in mL = dose in mg ÷ concentration in mg/mL.

For a 5 mg dose from a 20 mg/mL vial: 5 ÷ 20 = 0.25 mL, and 0.25 × 100 = 25 units. The same 5 mg from a 10 mg/mL vial is 0.5 mL, or 50 units. Because the dose is divided by the concentration, a stronger vial always needs fewer units for the same dose.

Zepbound and Mounjaro come in the same two families. Single-dose pens and vials hold each dose in 0.5 mL, and multi-dose vials and KwikPens hold four 0.6 mL doses in 2.4 mL (Zepbound prescribing information, section 3; Mounjaro prescribing information, section 3). The multi-dose column is the mg/mL those labels print; single-dose labels print only mg per 0.5 mL, so that column is the strength ÷ 0.5.

Drawn with a syringe, every branded single-dose vial dose is 50 units and every multi-dose vial dose is 60 units, at any strength. The strongest branded concentration is 30 mg/mL, in the 15 mg single-dose presentation. A compounded label above 30 mg/mL therefore puts more tirzepatide in each unit mark than any branded vial or pen.

Each cell is the dose ÷ the concentration × 100, rounded to one decimal place, at four example concentrations.

A 1 mL U-100 syringe holds 100 units (FDA alert on compounded semaglutide dosing errors). At 10 mg/mL, a 12.5 mg or 15 mg dose needs more than one full syringe, and the calculator warns whenever a result passes 100 units.

A vial labeled 5 mg / 0.5 mL is 10 mg/mL. Typing 5 into the mg/mL field would give 100 units for a 5 mg dose instead of 50, which is twice the dose. Type both numbers the way the label prints them, 5 mg / 0.5 mL, and the calculator divides them for you. A branded multi-dose carton works the same way: 60 mg/2.4 mL is 25 mg/mL (Zepbound prescribing information, section 3).

A refill at a different strength needs a new unit count for the same dose, which the vial transition calculator gives, and switching vial concentrations lists the checks to make before the first draw.

On a syringe with 1-unit marks, the calculator rounds the exact figure to the nearest whole unit and shows the mg that the rounded draw delivers. The table works this through at 24 mg/mL for each tirzepatide strength.

Small draws from strong vials lose the most, because one unit is a larger share of the dose. At 40 mg/mL, 2.5 mg is 6.25 units, and a 6-unit draw delivers 2.40 mg. To check a syringe you have already filled, the reverse dose calculator runs the formula backwards.

For a vial of powder mixed with bacteriostatic water, the concentration is the powder in mg divided by the water in mL. Tap "Mixed it yourself? Powder + water" in the calculator and enter both numbers. The table shows three doses at five powder and water combinations.

More water spreads the same powder across more unit marks. One unit holds 0.05 mg at 5 mg/mL and 0.4 mg at 40 mg/mL, so misreading the syringe by one unit costs eight times as much on the stronger vial.

Branded pens set the dose for you: the single-dose pen and the four-dose KwikPen deliver a fixed dose with no syringe. Branded vials are drawn to a fixed line, 0.5 mL from a single-dose vial and 0.6 mL from a multi-dose vial (Zepbound prescribing information, section 3), and the Zepbound vial calculator checks those draws. A compounded click pen is different again, and the compounded tirzepatide pen click calculator turns a dose into clicks from the pen’s mg/mL.

The calculator converts a dose you have been prescribed; it does not choose one. Zepbound starts at 2.5 mg once weekly and rises in 2.5 mg steps, each after at least 4 weeks on the current dose, up to 15 mg (Zepbound prescribing information, section 2). Each step, with the earliest week you can reach it, is in how the Zepbound dose ladder works. To divide a weekly dose into smaller injections, the split dose calculator rounds each draw and totals what the week delivers.

Every shot you log in Pensday is kept with its date, and a reminder arrives on your injection day.