Peptide Calculator: Units, mL and Cost per Dose

How to use this calculator

Start with the number printed on the vial label: the milligrams of freeze-dried powder inside. Type that into the vial box, or tap one of the common sizes. Next, enter the volume of water you added to dissolve it. The dose box takes micrograms or milligrams, and the toggle converts what you typed so the number never silently changes meaning. Finally, pick the syringe in your hand: 0.3 mL, 0.5 mL or 1 mL.

The result updates as you type. The big figure is the number of units to draw, and the vertical syringe on the left fills to the same mark. If the dose will not fit in the barrel you picked, the syringe turns amber and a warning explains why. The cost panel is optional: leave the price empty and it simply waits.

The formulas, step by step

Everything here is four lines of arithmetic on a U-100 insulin syringe, where 1 unit equals 0.01 mL. If you want to check the tool, you can run the same lines on any calculator.

• Concentration (mg/mL) = vial mg divided by water mL.
• Dose in mg = dose in mcg divided by 1,000 (skip this if you entered mg).
• Injection volume (mL) = dose mg divided by concentration.
• Syringe units = injection volume multiplied by 100.
• Doses per vial = vial mg divided by dose mg, counting whole doses only.

For cost, the price you paid is divided by the whole doses in the vial, then multiplied by your doses per week. The weekly total is simply the dose in mg times doses per week.

Worked examples

These four combinations are checked by hand and match the calculator exactly. The units column assumes a U-100 syringe.

The last row is the pre-filled example. A 30 mg vial in 3 mL gives 10 mg/mL. A 1.75 mg dose is 0.175 mL, or 17.5 units, and the vial holds 17 whole doses with a little left over. These are example inputs, not suggestions.

How to read the syringe

Hold the syringe upright with the needle at the bottom and read at eye level. The liquid level you care about is the edge of the black rubber stopper closest to the needle, not the rounded tip of it. A 1 mL U-100 barrel is usually marked every 2 units with a number at every 10, though spacing varies by brand, so count the ticks on your own syringe rather than trusting the picture. On a 0.3 mL barrel the same volume sits across a longer stretch, which is why small doses are easier to read on the smaller barrel.

A half unit is a judgement call between two ticks. If your mark lands there, the more reliable move is often to add a little more water so the mark falls on a clear line. The calculator warns you when a dose comes out under about 2 units for exactly that reason.

Common mistakes this tool is built to catch

• Treating units as mass. Ten units is 0.1 mL of liquid. It is not 10 mg and not 10 mcg. The drug in that 0.1 mL depends on the concentration.
• Mixing up mcg and mg. One mg is 1,000 mcg. Typing 250 into a box that expects mg asks for a dose far bigger than most vials. The tool warns when a dose exceeds the whole vial.
• Using the wrong syringe size. A 50 unit mark does not exist on a 0.3 mL barrel. Pick your barrel in the form so the warning and the picture match what you hold.
• Copying someone else's chart. A chart that says "draw 10 units" was built for one water volume. Change the water and every figure changes with it.
• Ignoring the leftover. A vial that divides into 17.14 doses gives you 17. The cost panel uses 17 for that reason.

Our longer guide to calculator mix-ups that cause real dosing errors walks through a five-check self-test.

Vials versus the prescription pen

Most of this site covers the prescription market, so it is worth being plain about what changes when you move to a vial. Wegovy and Zepbound are FDA-approved and come as prefilled pens. The pharmacy label names the drug and strength, a prescriber has chosen the step you are on, and there is no mixing, no syringe and no maths. You pay for that, and the cost comparison is what most readers come here for.

A research vial is the opposite trade. The powder may cost less per milligram, but you take on the reconstitution, the measuring and the checking yourself. There is no pharmacy label, no prescriber reviewing the dose and no approved-medicine status behind it. The weekly total in the calculator is there so you can set your arithmetic beside the dose steps printed in a pen's official prescribing information and see at a glance whether the two even resemble each other. For the full picture of what the approved options cost, see our guide to GLP-1 medications in 2026 and our look at trusted peptide and GLP-1 sources.

Peptide calculator questions

Keep exploring