Looking for a free online tirzepatide and Zepbound® dosage calculator for home use? This tool converts a doctor-prescribed tirzepatide dose from mg to mL and U-100 syringe units using the exact concentration printed on your vial label.
If your healthcare provider prescribed compounded tirzepatide for use at home, enter the prescribed dose and pharmacy concentration to estimate injection volume, doses per vial, and weeks of medication. This calculator does not select or recommend a dose.
This tool converts a prescribed tirzepatide dose in mg into liquid volume in mL. When a clinician or pharmacy has specifically instructed you to use a U-100 syringe, it also shows the corresponding syringe units.
The calculation uses the concentration printed on the vial: dose ÷ concentration = mL. For a U-100 syringe, mL × 100 = units. A 5 mg dose at 10 mg/mL, for example, equals 0.5 mL or 50 U-100 units.
Zepbound® prefilled pens are single-dose devices and should be used exactly as directed. This vial calculator is not intended to measure, divide, or transfer medication from a prefilled pen.
Many patients assume that a certain dose always equals the same number of units. That is not always true. A 2.5 mg dose of tirzepatide may equal one number of units at 5 mg/mL and a different number of units at 10 mg/mL or 20 mg/mL.
This is especially important for pharmacy-dispensed vials that may be prepared at different concentrations. Do not use another patient’s instructions, an old label, or a general chart in place of the directions provided with your medication.
• dose volume in mL
• units on a U-100 insulin syringe
• total medication in the vial
• estimated number of doses per vial
• estimated full doses
• estimated weeks of medication based on one injection per week
This comparison shows how common prescribed tirzepatide dose strengths convert at four example concentrations. Values assume a U-100 syringe, where 100 units equals 1 mL.
| Dose | 5 mg/mL | 10 mg/mL | 20 mg/mL | 25 mg/mL |
|---|---|---|---|---|
| 2.5 mg | 50 units | 25 units | 12.5 units | 10 units |
| 5 mg | 100 units | 50 units | 25 units | 20 units |
| 7.5 mg | 150 units | 75 units | 37.5 units | 30 units |
| 10 mg | 200 units | 100 units | 50 units | 40 units |
| 12.5 mg | 250 units | 125 units | 62.5 units | 50 units |
| 15 mg | 300 units | 150 units | 75 units | 60 units |
These are mathematical examples, not dosing instructions. If a calculated volume exceeds the capacity of your prescribed syringe, stop and contact your clinician or pharmacy.
A 2 mL vial at 10 mg/mL contains 20 mg total. This chart shows the mathematical volume, U-100 units, and number of complete doses available at each example dose.
| Dose | Volume | U-100 Units | Complete Doses |
|---|---|---|---|
| 2.5 mg | 0.25 mL | 25 units | 8 |
| 5 mg | 0.50 mL | 50 units | 4 |
| 7.5 mg | 0.75 mL | 75 units | 2 |
| 10 mg | 1.00 mL | 100 units | 2 |
| 12.5 mg | 1.25 mL | 125 units | 1 |
| 15 mg | 1.50 mL | 150 units | 1 |
First divide the prescribed dose in mg by the medication concentration in mg/mL. This gives the volume in mL. Then multiply the volume by 100 to estimate units on a U-100 insulin syringe.
The number of units depends on the medication concentration. A 2.5 mg dose may equal a different number of units if one vial is 5 mg/mL and another is 10 mg/mL or 20 mg/mL.
It can provide a mathematical estimate when the vial label clearly states the tirzepatide concentration in mg/mL and your clinician or pharmacy has instructed you to measure the dose with a U-100 syringe. It is not for Zepbound® prefilled pens.
The calculator divides the total medication in the vial by the entered dose and counts only complete doses. The weeks estimate assumes one injection per week and does not account for vial overfill, waste, priming, expiration, or a changing dose schedule.
Schedule a $79 medical weight loss consultation or review our separate Mounjaro® calculator and dosing charts.
Learn More About: Tirzepatide 2.5 mg For Weight Loss: Expected Results and Timeline
Florida Surgery and Weight Loss Center also provides several health calculators designed to help patients better understand weight loss eligibility, body composition, and nutrition planning during medical weight loss, GLP-1 treatment, or bariatric care.
Sergey Terushkin, MD, FACS, leads our telehealth medical weight loss program, offering personalized, prescription-based treatment plans tailored to each patient’s medical history, weight loss goals, and clinical evaluation.
All care is physician-directed and focused on safe, sustainable weight management using evidence-based medical therapies.
✅ It’s fast, affordable, and effective—start today!
📞 Call (954) 551-3508 or book online now!
Useful Links:
Explore before-and-after transformations from patients who received bariatric surgery and physician-guided weight-loss care at Florida Surgery And Weight Loss Center. Every patient’s journey is unique, and individual results vary.
Individual results vary. Photographs reflect the experiences of individual patients and do not guarantee similar outcomes.