MATH · FREE

Semaglutide Calculator

Vial and syringe arithmetic for a semaglutide powder that has to be mixed: concentration, mL to draw and units on a U-100 insulin syringe. Every number comes from your label or prescriber.

Pens do not need this

Branded semaglutide pens are prefilled and are not reconstituted (FDA label). This calculator is only for a product your prescriber or pharmacist told you to mix. It does not suggest any amount.

Math only. Not medical advice. This page does not recommend, suggest or check any dose. Use only the numbers from your prescriber, pharmacist or product label.

DRAW ON A U-100 SYRINGE

Concentration

Per syringe unit

of peptide in 1 unit

Volume to draw

Doses per vial

whole doses, rounded down

Math only. Not medical advice. This page does not recommend, suggest or check any dose. Use only the numbers from your prescriber, pharmacist or product label. Always check the numbers against your prescriber's or product's instructions.

AFTER YOU MEASURE

Measured it? Log the dose.

Log the dose and rotate injection sites in Orbido, a private log and reminder app for iPhone. No account, data stays on your device. Orbido is a logging tool, not medical advice.

Meet Orbido

Quick converters

Units ↔ mL (U-100)

Units

mg ↔ mcg

mcg

Worked example (made-up numbers)

These numbers show the arithmetic and are not a suggested amount. Say a vial label reads 3 mg, you add 1.5 mL of water, and the amount you want in the syringe is 300 mcg.

Concentration. 3 mg ÷ 1.5 mL = 2 mg/mL, which is 2,000 mcg per mL.
Volume. 300 mcg ÷ 2,000 mcg/mL = 0.15 mL.
Units. 0.15 mL × 100 = 15 units on a U-100 syringe.
Per unit. 2,000 mcg/mL ÷ 100 = 20 mcg in each unit.
Draws per vial. 3,000 mcg ÷ 300 mcg = 10 whole draws before any waste.

Units to mcg at this concentration

At 2 mg/mL every unit holds 20 mcg, so 5 units is 100 mcg, 10 units is 200 mcg and 25 units is 500 mcg. At a different concentration these figures change in proportion, which is why a unit mark can never be read without knowing the vial and the water added.

About the vial buttons

The buttons above the calculator (2, 3, 5, 10 mg) are example amounts that fill in the vial box so you can see how the numbers move. Enter what is printed on your label. This page does not say which products or sizes exist, and it does not endorse compounded or research-labeled vials. Follow the instructions from your prescriber and pharmacy.

Sources

FDA, OZEMPIC (semaglutide) injection prescribing information, 2025 label (accessed October 2026). Describes the branded product as a clear, colorless solution in prefilled, disposable, single-patient-use pens. Used only for the statement that branded pens are prefilled and not reconstituted.

Frequently asked questions

Is a semaglutide pen reconstituted?

No. The FDA label for the branded product describes a clear, colorless solution in prefilled, disposable, single-patient-use pens. There is nothing to mix, so this calculator does not apply to a pen.

When would I use a semaglutide calculator?

Only when you have a vial of powder that your prescriber or pharmacist told you to mix with a set volume of water. The calculator then turns the vial amount, the water and the amount to draw into mL and syringe units.

How many units is 0.15 mL on an insulin syringe?

15 units. On a U-100 syringe, units = mL × 100. Going the other way, 25 units is 0.25 mL. The marks measure volume, so how much semaglutide a unit holds depends on your vial's concentration.

How do I find mcg per unit?

Take the mg in the vial, divide by the mL of water, then multiply by 1,000 to get mcg per mL and divide by 100. For 3 mg in 1.5 mL that is 2 mg/mL, 2,000 mcg/mL and 20 mcg per unit.

Does this tell me how much semaglutide to use?

No. It never suggests an amount, a schedule or a change. Those come from your prescriber and the labeling for your product. The calculator only does division on the numbers you type.