Tirzepatide reconstitution calculator
Enter your vial amount, the bacteriostatic water you add and a dose, and this page gives the concentration and the units to draw on your syringe. It runs entirely in your browser: nothing you type is sent anywhere, and nothing is saved.
The buttons fill in 10 mg or 30 mg, the vial sizes people search for. They are not the only sizes: enter the number printed on your own vial.
Vial sizes people search for:
Blend components
Components share the one volume of bacteriostatic water above. The dose you entered applies to the component you select; the others follow from the same draw.
The maths for Tirzepatide
Three steps, the same as the main calculator: concentration is the vial content divided by the volume of bacteriostatic water, in mg per ml; the volume to draw is your dose in mg divided by that concentration; and the units to draw are that volume multiplied by your syringe's units per ml.
Worked example: a 10 mg vial of tirzepatide with 2 ml of bacteriostatic water, and a dose of 2.5 mg. The 2.5 mg figure is the labelled starting dose in the FDA prescribing information for Zepbound (revised August 2026), used because it is a checkable public number. It is an arithmetic illustration, not a suggestion. The 2 ml of water is an illustration too.
| Concentration | 10 mg ÷ 2 ml = 5 mg/ml |
|---|---|
| Volume to draw | 2.5 mg ÷ 5 mg/ml = 0.5 ml |
| U-100 syringe | 50 units |
| U-50 syringe | 25 units |
| U-40 syringe | 20 units |
How many doses in a vial
A vial holds its label amount divided by the dose, counted in whole doses; the water volume does not change the count. The doses in this table are arithmetic illustrations, not suggestions.
| Vial | Doses of 2.5 mg | Doses of 5 mg | Doses of 10 mg |
|---|---|---|---|
| 10 mg | 4 | 2 | 1 |
| 30 mg | 12 | 6 | 3 |
Reading the syringe
Syringe markings are units, not millilitres, and the conversion depends on which syringe you own. A U-100 syringe has 100 units per ml, so one unit is 0.01 ml. A U-50 has 50 units per ml and a U-40 has 40, so the same volume reads as a different number on each. This is why a dose must always be converted against the syringe actually in your hand, and why the syringe selector above changes the answer.
Questions
How much bac water for 10mg tirzepatide?
With 2 ml of bacteriostatic water, a 10 mg vial of tirzepatide is 5 mg/ml, so 2.5 mg reads as 50 units on a U-100 syringe. There is no single correct volume: water changes how many units you draw, not how many doses the vial holds.
How many units is 2.5 mg of tirzepatide?
At 5 mg/ml, which is a 10 mg vial with 2 ml of water, 2.5 mg of tirzepatide is 50 units on a U-100 syringe. At any other concentration the number changes, so work it from your own vial and water volume with the calculator above.
How many doses in a 30mg vial of tirzepatide?
A 30 mg vial of tirzepatide holds 12 of 2.5 mg, 6 of 5 mg, or 3 of 10 mg, counting whole doses only. The water volume does not change the count.
Reverse mode and blend mode are on the main calculator. The PinTrax app saves the vial and tracks what is left as you log doses.
Using a pen or a ready-to-use vial? See the guides.