This free semaglutide dosage calculator helps researchers convert a dose in milligrams into the matching volume and syringe units. Enter the vial size, the amount of water used for reconstitution and the target dose, and the tool does the arithmetic for you. It is designed to reduce simple math errors when working with reconstituted peptides in a lab or study setting.

Everything on this page is written in plain English and is for research and educational purposes only. The calculator does not decide what dose is appropriate for anyone. It simply converts numbers, so the accuracy of the result depends on the accuracy of the values you enter.

Semaglutide dosage chart

Weeks	Weekly dose
Weeks 1 to 4	0.25 mg
Weeks 5 to 8	0.5 mg
Weeks 9 to 12	1 mg
Weeks 13 to 16	1.7 mg
Week 17 onwards	2.4 mg (maintenance)

This chart shows the titration schedule most commonly published in the semaglutide literature, where the weekly dose is increased gradually every four weeks before reaching a maintenance level. It is included for reference only, so readers can see how published schedules are structured. It is not a recommendation, and it should not be used to plan treatment for any person. Real-world prescribing decisions are made by licensed healthcare professionals and can differ from this schedule.

How to reconstitute semaglutide

Research semaglutide is usually supplied as a lyophilized (freeze-dried) powder, most often in 5 mg or 10 mg vials. Before it can be measured, the powder is dissolved in a sterile diluent, typically bacteriostatic water. Common volumes are 1 mL, 2 mL or 3 mL. Adding more water makes the solution more dilute, which means each syringe unit holds less peptide. Many researchers choose a volume that makes their target doses land on easy-to-read unit markings.

Here is a worked example. A 5 mg vial reconstituted with 2 mL of water gives a concentration of 2.5 mg per mL (5 mg divided by 2 mL). On a standard U-100 insulin syringe, 1 mL equals 100 units, so each unit holds 0.025 mg. To measure 0.25 mg, you divide 0.25 by 2.5, which gives 0.1 mL, or 10 units. The calculator above performs these same steps automatically for any vial size and water volume.

How to use this calculator

Step 1: Enter the vial size:

Type the total amount of semaglutide in the vial, in milligrams, exactly as printed on the label. The most common sizes are 5 mg and 10 mg, but the calculator accepts any value. This number is the starting point for every other calculation, so double check it against the vial itself rather than relying on memory or an order confirmation.

Step 2: Enter the water volume:

Enter how much bacteriostatic water was added to the vial, in millilitres. If you have not reconstituted the vial yet, you can try different volumes here to see how each one changes the concentration and the number of units per dose. The tool then shows the final concentration in mg per mL so you can confirm it matches your own working.

Step 3: Enter the target dose:

Type the dose you want to measure, in milligrams. If your notes are written in micrograms, remember that 1 mg equals 1,000 mcg, so 0.25 mg is the same as 250 mcg. The calculator converts the target dose into a volume based on the concentration from Step 2. Entering the dose in the wrong unit is one of the most common sources of error, so take a moment to confirm it.

Step 4: Read the syringe units:

The result shows the volume in millilitres and the equivalent number of units on a U-100 insulin syringe. It also estimates how many doses of that size the vial contains. If the result looks unusual, such as a very small fraction of a unit or a volume larger than your syringe, go back and check each input. The calculator assumes a U-100 syringe, so results will not match syringes with different markings.

Frequently asked questions

How many units is 0.25 mg of semaglutide?

It depends on the concentration of the solution. With a 5 mg vial and 2 mL of water (2.5 mg/mL), 0.25 mg is 0.1 mL, which is 10 units on a U-100 syringe. With a 5 mg vial and 1 mL of water (5 mg/mL), the same 0.25 mg is 5 units. Because the answer changes with every concentration, entering your own values into the calculator is the most reliable way to check.

How long does a 5 mg vial of semaglutide last?

A 5 mg vial contains 20 doses of 0.25 mg, 10 doses of 0.5 mg, 5 doses of 1 mg or about 2 doses of 2.4 mg. On a once-weekly schedule, the arithmetic can suggest many weeks of supply at low doses. However, a reconstituted vial is generally considered usable for around 28 days when bacteriostatic water is used, so the in-use period often limits how long a vial lasts more than the amount of peptide inside it.

What is the difference between semaglutide and tirzepatide?

Semaglutide is a GLP-1 receptor agonist, meaning it acts on one hormone receptor (glucagon-like peptide-1). Tirzepatide is a dual agonist that acts on both the GIP and GLP-1 receptors. The two compounds have different molecular structures, different published dosing ranges and different titration schedules, so a calculation made for one should never be reused for the other.

How do I store reconstituted semaglutide?

Once mixed with water, semaglutide is commonly kept in a refrigerator at 2 to 8°C, protected from light, and should not be frozen. Label the vial with the date it was reconstituted and discard it after the in-use period, which is usually about 28 days with bacteriostatic water. Any solution that looks cloudy, discoloured or contains particles should not be used.

Disclaimer: Semaglutide is a prescription medication in many countries. This calculator and the information on this page are provided for research and educational purposes only. They are not medical advice and are not a substitute for guidance from a qualified healthcare professional. Always verify your calculations independently.