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Zepbound (tirzepatide) comes as a single-dose pen, a multi-dose KwikPen, and vials you draw up yourself, which since early 2026 come in single-dose and multi-dose versions. Units only matter for the vials: your prescription is in mg, a single-dose vial holds 0.5 mL, a multi-dose vial gives four 0.6 mL doses, and insulin syringes read in units. This calculator converts between all three in seconds.
This changes the conversion because dose volume differs between devices.
Enter a value above to see results.
This calculator shows general arithmetic only, not dosing advice. Always follow your prescriber and official instructions.
Quick facts
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If you use the Zepbound pen, you never see a unit. It's a fixed-dose auto-injector: press it against your skin, it delivers the full 0.5 mL, done. No dial, no syringe, no math. The multi-dose KwikPen is the same idea in a different shape: four fixed 0.6 mL doses, a knob you turn to the stop, still no syringe.
The vials are different. There are two on the label: the original single-dose vial (one 0.5 mL dose) and, since the February 2026 label update, a multi-dose vial holding four 0.6 mL doses. LillyDirect's self-pay prices cover the single-dose vial and the KwikPen. With either vial you draw each dose up yourself. The FDA prescribing information says to use a syringe appropriate for the dose, for example a 1 mL syringe that can measure a 0.5 mL or 0.6 mL dose. In practice, many people end up with U-100 insulin syringes, and those are marked in units rather than mL. So you're holding a prescription in mg, a vial labeled in mg, and a syringe that reads in units. That's the exact gap this calculator fills.
Two numbers worth memorizing: a full dose from a single-dose vial is always 50 units (0.5 mL) on a U-100 syringe, and a full dose from a multi-dose vial is always 60 units (0.6 mL), whatever the strength. Within each format, the difference between strengths is concentration, not volume. It also means the two vial types are not interchangeable in the math: a 5 mg single-dose vial is 10 mg per mL, while a multi-dose vial with 5 mg doses is about 8.3 mg per mL. Match the calculator's device option to the vial in your hand.
Units are a way of measuring volume on a U-100 syringe (100 units = 1 mL). Vial strength changes the concentration (mg per mL), so the same number of units contains a different amount of medicine depending on which strength you have.
The calculator uses three values: the strength in mg per dose, the dose volume for your format (0.5 mL for the single-dose pen and vial, 0.6 mL for the multi-dose vial and KwikPen), and the U-100 definition (100 units = 1 mL). Pick the device option that matches your container; the formulas below use the single-dose 0.5 mL as the example.
Single-dose shortcut (because 0.5 mL = 50 units):
mg = (units ÷ 50) × vial strength
For example, 25 units from a 5 mg vial: (25 ÷ 50) × 5 = 2.5 mg
Multi-dose shortcut (because 0.6 mL = 60 units):
mg = (units ÷ 60) × strength per dose
For example, 30 units from a multi-dose vial with 5 mg doses: (30 ÷ 60) × 5 = 2.5 mg
This table shows the basic relationship between U-100 units and mL. It's the same for every strength:
| Units (U-100) | mL |
|---|---|
| 5 | 0.05 |
| 10 | 0.10 |
| 20 | 0.20 |
| 25 | 0.25 |
| 30 | 0.30 |
| 40 | 0.40 |
| 50 | 0.50 |
Read across from your syringe units to see roughly how many mg each single-dose strength delivers. The table uses the same formulas as the calculator above, and 50 units is the full dose for every single-dose strength. This table does not apply to the multi-dose vial or KwikPen: their full dose is 60 units and the concentrations are lower, so use the calculator's multi-dose option instead.
| Units | mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 5 | 0.05 | 0.25 | 0.50 | 0.75 | 1.00 | 1.25 | 1.50 |
| 10 | 0.10 | 0.50 | 1.00 | 1.50 | 2.00 | 2.50 | 3.00 |
| 15 | 0.15 | 0.75 | 1.50 | 2.25 | 3.00 | 3.75 | 4.50 |
| 20 | 0.20 | 1.00 | 2.00 | 3.00 | 4.00 | 5.00 | 6.00 |
| 25 | 0.25 | 1.25 | 2.50 | 3.75 | 5.00 | 6.25 | 7.50 |
| 30 | 0.30 | 1.50 | 3.00 | 4.50 | 6.00 | 7.50 | 9.00 |
| 35 | 0.35 | 1.75 | 3.50 | 5.25 | 7.00 | 8.75 | 10.50 |
| 40 | 0.40 | 2.00 | 4.00 | 6.00 | 8.00 | 10.00 | 12.00 |
| 45 | 0.45 | 2.25 | 4.50 | 6.75 | 9.00 | 11.25 | 13.50 |
| 50 | 0.50 | 2.50 | 5.00 | 7.50 | 10.00 | 12.50 | 15.00 |
Pick a target mg, then read across to find the approximate units for each single-dose vial strength. Values are rounded to the nearest half unit. A dash means the target is more than one full vial of that strength.
| Single-dose vial | 0.5 mg | 1 mg | 2.5 mg | 3 mg | 5 mg |
|---|---|---|---|---|---|
| 2.5 mg | 10 u | 20 u | 50 u | – | – |
| 5 mg | 5 u | 10 u | 25 u | 30 u | 50 u |
| 7.5 mg | 3.5 u | 6.5 u | 16.5 u | 20 u | 33.5 u |
| 10 mg | 2.5 u | 5 u | 12.5 u | 15 u | 25 u |
| 12.5 mg | 2 u | 4 u | 10 u | 12 u | 20 u |
| 15 mg | 1.5 u | 3.5 u | 8.5 u | 10 u | 16.5 u |
The vials exist because of price. LillyDirect's self-pay program sells Zepbound directly to patients without insurance coverage, and single-dose vials are a core part of that offer. As of July 2026:
Prices have changed more than once this year, so check lilly.com for the current terms before you rely on any figure here.
The tables and calculator show pure arithmetic based on labeled strengths and volumes. In real-world use, the official instructions matter more. If the math and the instructions ever conflict, the instructions win.
Log your weekly Zepbound dose in units, mL, or mg and see your weight trend alongside it.
Sign up freeZepbound Prescribing Information (Lilly USPI)
Lilly, Zepbound US Prescribing Information covers the 0.5 mL and 0.6 mL dose volumes, the single-dose and multi-dose presentations, syringe guidance, missed-dose rule, and storage.
FDA approval label for Zepbound
FDA, Zepbound label (NDA 217806) is the original approval label on the FDA's drug database.
DailyMed entry for Zepbound
DailyMed, Zepbound (tirzepatide) injection lists the single-dose pen and vial presentations (0.5 mL each) plus the multi-dose vial and KwikPen (four 0.6 mL doses each).
LillyDirect self-pay terms
Lilly, Zepbound self-pay full terms and conditions sets out vial pricing and the 45-day refill window.
Zepbound savings card
Lilly, Zepbound savings and support covers the commercial-insurance savings card and its government-program exclusions.
Medicare GLP-1 Bridge
CMS, Medicare GLP-1 Bridge is the official page for the $50 copay program that runs July 1, 2026 to December 31, 2027 and covers the Zepbound KwikPen. Medicare's fact sheet (PDF) explains eligibility and that the $50 copay does not count toward the Part D out-of-pocket cap.
List price reference
GoodRx, Zepbound prices tracks the list price and pharmacy cash prices.
Last reviewed: July 2026