GLP-1 Calculator
This GLP-1 calculator does the dose-to-units maths for the three GLP-1 compounds sold as powder vials: tirzepatide, semaglutide and retatrutide. The maths is the same for all three. The numbers are not. Semaglutide amounts are fractions of a milligram, the other two run in whole milligrams, and the vial sizes differ. Pick your compound, enter the vial and the water, and get the exact draw in units.
Units measure volume, not dose. The same units on a different mix are a different dose.
The link holds only the numbers you typed. No account, no tracking, nothing else.
The calculator starts on tirzepatide. Use the compound menu at the top of it to switch to semaglutide or retatrutide, or jump to a compound's own page from the cards further down.
On this page
How this GLP-1 calculator handles three compounds
GLP-1 is the family name, short for glucagon-like peptide-1, and the family is where the confusion starts. Three different compounds share the label, and people carry unit numbers from one to another as if the numbers were interchangeable. They are not, for two plain arithmetic reasons.
First, the dose scales differ. Semaglutide amounts are worked in fractions of a milligram: a quarter, a half, one milligram. Tirzepatide and retatrutide amounts are whole milligrams, several times larger on paper. Second, the vials differ. Semaglutide powder comes in vials from 5 to 30 mg. Tirzepatide and retatrutide run from 5 to 60 mg. Different amounts in different vials mean different concentrations, and the concentration is what decides the draw.
Underneath, the calculation never changes: vial amount divided by water is the concentration, dose divided by concentration is the volume, volume times 100 is the units. What changes is only which numbers go in. That is why this page keeps the three compounds in separate tables instead of merging them into one.
Dose to units, compound by compound
Three tables, one per compound, each built from that compound's own vial sizes. Find your compound first, then your mix, then read across to your amount.
Tirzepatide
The biggest vials of the three and whole-milligram amounts, so the draws land in the middle of the syringe.
| Vial | Water | Concentration | 2.5 mg draw | 5 mg draw | 10 mg draw |
|---|---|---|---|---|---|
| 20 mg | 2 mL | 10 mg/mL | 25 units | 50 units | 100 units |
| 30 mg | 2 mL | 15 mg/mL | 16.7 units | 33.3 units | 66.7 units |
| 60 mg | 3 mL | 20 mg/mL | 12.5 units | 25 units | 50 units |
Semaglutide
The smallest amounts of the three, in fractions of a milligram. Watch the strong mixes: the draws sit down at the first marks on the barrel.
| Vial | Water | Concentration | 0.25 mg draw | 0.5 mg draw | 1 mg draw |
|---|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 10 units | 20 units | 40 units |
| 10 mg | 2 mL | 5 mg/mL | 5 units | 10 units | 20 units |
| 10 mg | 1 mL | 10 mg/mL | 2.5 units | 5 units | 10 units |
Retatrutide
Large vials again, and the widest spread of concentrations, because the catalogue runs from 5 mg all the way to 60 mg.
| Vial | Water | Concentration | 1 mg draw | 2 mg draw | 4 mg draw |
|---|---|---|---|---|---|
| 10 mg | 2 mL | 5 mg/mL | 20 units | 40 units | 80 units |
| 20 mg | 2 mL | 10 mg/mL | 10 units | 20 units | 40 units |
| 40 mg | 3 mL | 13.33 mg/mL | 7.5 units | 15 units | 30 units |
Read down any single column and the lesson repeats. The same amount is a big draw from one mix and a small draw from another, in all three compounds, every time. A unit number quoted without its vial and its water means nothing anywhere in this family.
Vial or pen: not the same product
Two of these compounds exist as approved medicines, and it is worth being precise about what those products are. Semaglutide is FDA-approved as Ozempic and Wegovy, prefilled pens, and as Rybelsus, a tablet. Tirzepatide is FDA-approved as Mounjaro and Zepbound, prefilled pens. A pen arrives measured. There is no water to add, no mixing, and no draw to work out, so nothing on this page applies to the pens or the tablets.
The powder vials are a different thing wearing the same compound name. They are research products, sold as loose powder to be mixed with water and measured by hand, and they are not the approved medicines. Retatrutide goes one step further: it has no approved product at all, under any brand, because it is still in clinical trials.
The hand-measured part is where the risk sits. The FDA has published safety communications about people mis-measuring compounded GLP-1 products after confusing units, millilitres and milligrams, some of them ending up in hospital. That record is why every result on this site shows your dose in both mg and mcg, right next to the units, and why the tables above never quote a unit number without its mix.
Each compound's own calculator
This page is the family overview. Each compound also has its own page, with the calculator preset for it, fuller tables for its vial range, and the questions people ask about that compound on its own.
Common questions
What is a GLP-1 calculator?
A calculator that does the dose-to-units maths for GLP-1 powder vials. You give it the amount on the vial label and the water you added, it works out the concentration, and then it turns your dose into the draw in units on a U-100 syringe. This one covers the three GLP-1 compounds sold as powder vials: tirzepatide, semaglutide and retatrutide. Same three steps as every calculator on this site.
How many units is 2.5 mg of tirzepatide?
It depends on the mix, which is the whole point of this page. From a 20 mg vial mixed with 2 mL of water, 2.5 mg is 25 units. From a 60 mg vial mixed with 3 mL, the same 2.5 mg is 12.5 units. The tirzepatide table above covers the common mixes, and the tirzepatide calculator page goes deeper.
How many units is 0.5 mg of semaglutide?
From a 5 mg vial mixed with 2 mL of water, 0.5 mg is 20 units. From a 10 mg vial mixed with 1 mL, it is 5 units. Semaglutide draws run small, because the amounts themselves are fractions of a milligram. The semaglutide table above has the common mixes.
Can I use this calculator for an Ozempic or Mounjaro pen?
No, and there is nothing to calculate. The approved pens arrive pre-measured, with no water to add and no draw to work out. This calculator is only for powder vials, which are mixed by hand. Powder vials are also not the approved products, even when the compound name matches. They are research products, and the pen is a regulated medicine.
Is retatrutide an approved GLP-1 medicine?
No. Retatrutide is investigational. It is in Phase 3 clinical trials and has not been approved by the FDA or by any other medicines regulator, for any use. Semaglutide and tirzepatide both have approved brands. Retatrutide has none, under any name.
How many doses are in a GLP-1 vial?
Vial amount divided by dose. The water changes the size of each draw, never the count. A 30 mg tirzepatide vial at 5 mg an amount holds 6 doses. A 10 mg semaglutide vial at 0.5 mg an amount holds 20. The calculator shows the count for your own numbers, including any leftover too small to be a full dose.
Arithmetic only
This calculator does maths on the numbers you enter. It works out concentration, draw volume and syringe units from the vial amount and water volume you give it. Nothing more.
It does not recommend amounts, schedules or products, and it does not know what is in your vial. It uses the amount printed on the label. If the label and the actual contents differ, the result differs too. For medical questions, talk to a clinician.
How the maths works, and where the facts on this site come from: Methodology and sources.
Report an error or ask a question
Found a wrong number on this page, or stuck on the maths? Send a correction or a question here. Confirmed errors get fixed and written into the change log on the Methodology page.