Tirzepatide Dosage Calculator

Concerned about side effects? See Tirzepatide side effects — what the research documents (honest, sourced, research-use-only).

A tirzepatide dosage calculator does one job, and does it exactly: it turns two numbers you already have — the milligrams of peptide in your vial and the milliliters of bacteriostatic water you mix in — into the precise syringe reading for whatever target dose you want to draw. Reconstituted peptides are measured by volume, not by milligrams, so the same 2.5 mg dose can read as 50 units on one vial and 25 units on another depending only on how much water you added. Getting that conversion right is the whole task, and it is pure arithmetic with no guesswork. This page lays out the formulas, walks a complete worked example with real catalog numbers, and gives you a tirzepatide units calculator reference table for the entire 2.5–15 mg titration ladder.

How the tirzepatide dosage calculator works

Tirzepatide ships as a lyophilized (freeze-dried) powder inside a sealed vial. On its own the powder cannot be measured into a syringe, so it is reconstituted — dissolved into a known volume of bacteriostatic water. Once dissolved, every milliliter of that solution carries a fixed amount of peptide. That amount is the concentration, and it is the hinge the whole calculation swings on.

The calculator asks you three things: how many milligrams are in the vial, how many milliliters of bacteriostatic water you added, and the target dose in milligrams. From those it derives the concentration, the volume you need to draw, the reading in units on a U-100 insulin syringe, and how many doses the vial holds. Change any one input and the outputs update, which is exactly why a fixed “tirzepatide is X units” answer you see repeated online is meaningless without the reconstitution behind it.

The math behind it

Four short formulas run the entire tool. They are universal to every reconstituted peptide, not specific to any brand or protocol:

• Concentration (mg/mL) = vial mg ÷ bacteriostatic water mL. How much peptide sits in each milliliter of solution.
• Draw volume (mL) = dose mg ÷ concentration. The volume of solution that contains your target dose.
• Units on a U-100 syringe = draw mL × 100. A U-100 syringe is graduated so that 1 mL equals 100 units, so multiplying the draw volume by 100 gives the mark to fill to.
• Doses per vial = vial mg ÷ dose mg (rounded down to a whole number). How many full doses the vial yields.

One unit conversion trips people up more than any other, so keep it in front of you: 1 mg = 1000 mcg, which means 250 mcg = 0.25 mg and 500 mcg = 0.5 mg. Tirzepatide doses are large enough that they are almost always written in milligrams, but if a figure ever appears in micrograms, convert to milligrams before it enters the formula.

Worked example: 10 mg vial + 2 mL, 2.5 mg dose

Take the most common tirzepatide starting scenario using real numbers from this catalog: a 10 mg vial, reconstituted with 2 mL of bacteriostatic water, drawing a 2.5 mg target dose on a U-100 syringe. Run the four formulas in order:

1. Concentration = 10 mg ÷ 2 mL = 5 mg/mL. Each milliliter of your solution holds 5 mg of tirzepatide.
2. Draw volume = 2.5 mg ÷ 5 mg/mL = 0.5 mL. Half a milliliter contains the 2.5 mg dose.
3. Units = 0.5 mL × 100 = 50 units. Fill the U-100 syringe to the 50-unit mark.
4. Doses per vial = 10 mg ÷ 2.5 mg = 4 doses. The vial yields four full 2.5 mg draws.

Notice what did not happen: adding water never changed how much tirzepatide is in the vial — it is still 10 mg total. Water only spreads that fixed amount across a larger or smaller volume, which changes the concentration and therefore the units you draw. This is the single most useful thing to internalize about reconstitution.

How much bacteriostatic water should you use?

There is no single correct fill volume — only trade-offs, and the calculator handles whichever you pick. More water lowers the concentration, so each dose becomes a larger, easier-to-read volume on the syringe; less water raises the concentration, shrinking the volume so more doses fit in a set number of syringe units. Two practical boundaries frame the choice:

• The water has to physically fit in the vial. Small peptide vials often hold only 3 mL or so of headspace. A 5 mg or 10 mg tirzepatide vial comfortably takes 1–2 mL; the 30 mg vial is larger and accommodates 3 mL without trouble. Never plan a fill the vial cannot actually hold.
• Keep the draw readable. Very high concentrations push doses down to a handful of units, where small measurement slips become large percentage errors. Very low concentrations can push a dose past the 100-unit end of a single syringe. Aim for a concentration that lands your usual dose somewhere in the middle of the syringe scale.

Common tirzepatide reconstitutions land at 5 mg/mL or 10 mg/mL because they produce clean, whole-number unit readings across the titration ladder. Whatever you choose, the reconstitution guide walks the full mixing procedure step by step: peptide reconstitution guide.

Reading units on a U-100 syringe

A U-100 insulin syringe is the standard tool here, and its scale is the source of most confusion. The “100” means the full barrel holds 1 mL, divided into 100 units — so 1 unit = 0.01 mL. The numbers printed on the barrel are units, not milligrams and not milliliters. When the calculator says “50 units,” it means fill to the mark labeled 50, which is halfway up a 1 mL syringe.

Because units are just hundredths of a milliliter, the conversion is always the same: multiply your draw volume in mL by 100. A 0.25 mL draw is 25 units, a 0.5 mL draw is 50 units, a 0.75 mL draw is 75 units, and a full 1.0 mL draw is 100 units — the entire syringe. Anything larger than 1.0 mL will not fit in one U-100 syringe and has to be split into two draws or reconstituted more concentrated.

Vial-size reconstitution reference

This site stocks tirzepatide in 5 mg, 10 mg, 15 mg, and 30 mg vials. The table below shows a sensible bacteriostatic-water fill for each, the concentration it produces, and what a 2.5 mg and a 5 mg dose read as in units. Use it to sanity-check the calculator, or to match a vial you already have to a target concentration.

The 5 mg and 10 mg vials at these fills land on the identical 5 mg/mL concentration, so a given dose reads the same units on either — the larger vial simply holds more doses. The 15 mg and 30 mg vials at these fills both reach 10 mg/mL, halving the volume (and units) for the same dose.

Tirzepatide titration-to-units table

Tirzepatide is a once-weekly subcutaneous compound, and the widely reported approach is to start low and step up gradually — commonly 2.5 mg, then 5, 7.5, 10, 12.5, and up to 15 mg weekly, with several weeks held at each step. The table below is a tirzepatide units calculator in table form: it shows each rung of that ladder converted to draw volume and units at two of the most common concentrations, so you can read your dose straight off whichever reconstitution you used.

Titration figures here reflect commonly reported research schedules, not a personalized recommendation. For documented, compound-specific specifics, see the reference library: single-peptide dosage reference.

Mistakes the calculator catches

Running the arithmetic explicitly, instead of trusting a remembered number, prevents the errors that actually happen with reconstituted tirzepatide:

• Reading units as milligrams. Drawing to the “25” mark thinking it means 25 mg is a tenfold-plus error. The barrel is graduated in units, and units convert to a dose only through your specific concentration.
• Assuming a fixed unit count. “2.5 mg is 25 units” is only true at 10 mg/mL. At 5 mg/mL that same 2.5 mg is 50 units. Concentration must always come first.
• Thinking more water means less drug. Adding water changes concentration, never the total milligrams in the vial. The vial holds the same total dose count regardless of fill volume.
• Micrograms versus milligrams. Any stray microgram figure must be divided by 1000 before use — 250 mcg is 0.25 mg, not 250 mg.
• Overfilling the syringe. A dose that computes above 100 units cannot fit in one U-100 syringe; the calculator surfaces this so you rethink the reconstitution before drawing.

What tirzepatide is studied for

Tirzepatide is a dual GIP/GLP-1 receptor agonist — it engages two incretin pathways rather than one — and it has been studied primarily for weight loss and metabolic outcomes. In the SURMOUNT-1 trial, participants on the highest dose reported roughly 22.5% average body-weight reduction over the study period, one of the larger effects seen in the incretin class. It is administered as a once-weekly subcutaneous injection and dosed in milligrams, which is why the reconstitution and unit math on this page matters: the compound is prepared from powder, and every dose depends on getting concentration right. Those figures are reported trial results, not a claim about outcomes for any individual.

Run your own numbers

Enter your vial size, water volume, and target dose above and the tirzepatide dosage calculator returns concentration, draw volume, units, and doses per vial instantly — for any of the 5, 10, 15, or 30 mg vials. If you want to talk a scenario through, ask the OpenPeptide assistant on the dosagepeptide.com home page, and for documented compound specifics head to the single-peptide dosage reference.