Semaglutide Dose Calculator

How the conversion works

Compounded semaglutide — the molecule in Ozempic and Wegovy — is prescribed in milligrams but drawn in units on a U-100 insulin syringe. Units measure volume: 100 units = 1 mL, so 1 unit = 0.01 mL regardless of what the vial contains. The concentration on the label is the only thing that turns that volume into a dose:

units = (dose in mg ÷ concentration in mg/mL) × 100

Enter your dose and your vial's mg/mL and the calculator returns the unit mark to draw to, the exact unrounded figure and the volume in mL. If your vial came as powder, switch to Reconstituted vial and enter the milligrams of powder and the millilitres of water: 5 mg of powder in 2 mL is 2.5 mg/mL, and the same 5 mg in 1 mL is 5 mg/mL.

Why the volumes are so small, and why that matters

Semaglutide doses are roughly a tenth the size of tirzepatide doses, so vials are supplied dilute — the presets above run from 1 to 5 mg/mL. Even so, a starting 0.25 mg dose at 5 mg/mL is 5 units, which is 0.05 mL. Misread that by a single unit and you are 20% out. The same one-unit slip on a 50-unit draw is 2%. Nothing about the syringe changes; the relative stakes of a small error do.

The arithmetic cuts the other way too. The same 0.25 mg occupies 25 units at 1 mg/mL — five times more of the barrel, and correspondingly easier to read. If you are comparing two pharmacies' vials, the concentration decides how legible your early doses will be.

Units per dose at three common concentrations

A 100-unit syringe holds 1 mL and no more, so the dilute vial that made your 0.25 mg dose easy to read cannot deliver 1.7 mg in one draw. Concentration that suits the bottom of the ladder does not suit the top, which is why a refill part-way through titration is a reasonable moment to expect the mg/mL to have changed.

The label trap

A vial marked "2.5 mg / 0.5 mL" is 5 mg/mL — halving the volume doubles the concentration. Enter 2.5 from that label and the calculator will tell you to draw twice the volume you need. Divide the milligrams by the millilitres before you enter anything, and treat a vial that states only a total strength the same way: 10 mg in 4 mL is 2.5 mg/mL.

Two ladders, and two things people get wrong

Semaglutide has different labelled schedules under its two brand names, and compounded vials carry neither — the target you are climbing towards comes from your prescriber.

Ozempic escalates 0.25 → 0.5 → 1 → 2 mg once weekly. Two milligrams is the maximum; there is no 2.4 mg Ozempic dose, a figure that gets borrowed from Wegovy and repeated on forums. Wegovy escalates 0.25 → 0.5 → 1 → 1.7 → 2.4 mg, and since 2026 a further step to 7.2 mg is permitted after at least four weeks tolerating 2.4 mg. 1.7 mg is also a permitted maintenance dose. So "2.4 mg is the maximum" is wrong in both directions — too high for Ozempic, too low for Wegovy. For scale, 7.2 mg at 5 mg/mL would be 144 units, well past what one syringe holds.

The four-week interval between steps is not arbitrary. Semaglutide reaches steady state after roughly four to five weeks of once-weekly dosing, so a step judged at two weeks is judged before the level has settled. The labelling is also explicit that 0.25 mg is a starting dose rather than a maintenance dose.

Where this calculator does not apply

Ozempic and Wegovy pens deliver fixed, pre-set doses — no units, no volume, nothing to convert. Oral semaglutide is a tablet, so the question does not arise at all. Unit arithmetic belongs to compounded vials, which is also the setting with the least standardisation: concentrations vary between pharmacies and between consecutive refills from the same one. Whatever this tool returns, check it against the vial in your hand and the dose on your prescription before you draw.