Peptide calculator

How the calculator works

Three numbers go in: the peptide in the vial, the water you added, and your dose. From them the calculator finds how strong the mix is, how much of it holds one dose, and where that volume sits on a U-100 insulin syringe or on the dial of a reusable pen.

Concentration

peptide in the vial ÷ water added = mg per mL

Volume of one dose

dose ÷ concentration = mL

Units on a U-100 syringe or pen

mL × 100 = units

Doses in the vial

peptide in the vial ÷ dose, whole doses only

The dose can be in mcg or mg; 1 mg is 1,000 mcg, and the answer repeats the dose in both. A vial labelled in IU takes a dose in IU: IU and mg are not converted here, because how many IU a milligram holds depends on the product.

The exact value and the marks you can draw

The answer gives the exact number of units first. When it falls between two lines on the syringe, nothing is rounded quietly: the calculator names the two nearest lines and the dose each one holds, and says which is nearer.

• A 1 mL U-100 syringe is marked every 2 units or every unit, a 0.5 mL syringe every unit, and a 0.3 mL syringe every unit or every half unit. Pick yours under Syringe.
• Under 2 units is hard to measure accurately, and the answer says so. Adding more water to the vial makes each unit hold less, so a small dose takes more units.
• A dose that does not fit the syringe, or that is smaller than its first line, is shown as a limit rather than a number.

Syringe or pen

Insulin syringes and reusable insulin pens use the same U-100 scale: 100 units is 1 mL, so 1 unit is 0.01 mL whichever you measure with. The 0.3, 0.5 and 1 mL syringes differ in how much they hold (30, 50 and 100 units) and how far apart their lines are, not in the size of a unit.

A reusable pen takes a 3 mL cartridge, 300 units. It dials whole steps, 1 unit or ½ unit depending on the model, up to its largest dose: 60 units on NovoPen 6 and HumaPen Savvio, 30 on the half-unit NovoPen Echo and HumaPen Luxura HD, 80 on AllStar PRO. Pick your model under Pen, or keep the typical pen and check its dial.

Units to dial

the units above, on the pen’s step; between two steps, both are shown with the dose each holds

Shots

units ÷ the pen’s largest dose, rounded up; the units split as evenly as the step allows

Units in the cartridge

mix in the cartridge (mL) × 100

Doses in the cartridge

units in the cartridge ÷ (units per dose + priming shot × shots), whole doses only

Before each injection a pen is primed: the makers’ instructions for NovoPen 6 and AllStar PRO have you dial 2 units and push them out until a drop shows at the needle tip. That mix leaves the cartridge too, so the calculator counts it: in the example, a 10-unit dose and a 2-unit priming shot take 12 units, and a full cartridge gives 300 ÷ 12 = 25 doses. Change the priming shot if your pen’s instructions say otherwise, and enter the mix in the cartridge if it is not full.

Ozempic, Wegovy, Mounjaro and Zepbound pens are not calculated here: they give the fixed doses on their labels and are not marked in units. Their label schedules are on the GLP-1 dose charts.

Other calculators

• Peptide reconstitution calculatorThe water to add to the vial so your dose is the number of units you want to draw.
• Insulin syringe units to mLUnits on a U-100 insulin syringe in mL, and mL in units.
• Tirzepatide dosage calculatorUnits to draw for a tirzepatide dose, from the mg in the vial and the mL of liquid in it.
• Semaglutide units to mgThe mg in the units you draw of a semaglutide vial, or the units for a dose, from the strength printed on the vial.
• Units to mg converterThe mg in the units you draw, or the units for an amount in mg, from the strength of your vial.
• GLP-1 dosage chartsStart, step-up, maintenance and maximum doses of each GLP-1 medicine as its FDA label gives them, with the label's date.
• NAD+ injection calculatorUnits to draw for an NAD+ dose, from the mg in the vial and the mL of liquid in it.
• HGH reconstitution calculatorUnits to draw for an HGH dose in IU or mg, from the vial and the water you added.
• Retatrutide dosage calculatorUnits to draw for a retatrutide dose, from the mg in the vial and the water you added.

Questions

How many units is 1 mg?

It depends on the water in the vial. At 2.5 mg per mL (5 mg in 2 mL), 1 mg is 0.4 mL, which is 40 units. At 5 mg per mL (10 mg in 2 mL), it is 0.2 mL, 20 units. Enter your vial and water above to see yours.

How much water should I add to the vial?

The water does not change the dose, only how many units hold it. More water spreads the peptide thinner, so each unit holds less and a small dose is easier to measure; less water keeps a large dose within one syringe. The reconstitution calculator works backwards from the units you want to draw.

Is a unit the same on a 0.3 mL and a 1 mL syringe?

Yes. On every U-100 syringe 100 units is 1 mL. A 0.3 mL syringe holds 30 units and a 1 mL syringe 100; the smaller one has lines closer together, which makes small doses easier to read.

Why does the answer show two marks?

Because the exact volume falls between two lines of the syringe or two steps of the pen. You see the exact value and the dose the line on either side holds, so the choice between them is yours.

Does the pen mode work with an Ozempic or Mounjaro pen?

No. Those pens give the doses printed on their labels and are not marked in units. The pen mode is for reusable U-100 pens that take a 3 mL cartridge.

Sources

• BD Insulin Syringe, 510(k) K190054FDA, cleared 2019-10-21. The U-100 scale and the 0.3, 0.5 and 1 mL barrels with their lines.
• Ultra-Fine SAFETY Insulin Syringe, 510(k) K260208FDA, cleared 2026-07-13. U-100 syringes and their scale markings.
• HumaPen Savvio, 510(k) K160668FDA, decision 2016-06-03. A reusable 3 mL cartridge pen dialling 1 to 60 units in 1-unit steps.
• NovoPen Echo, 510(k) K182387FDA, decision 2018-12-17. A reusable 3 mL cartridge pen dialling 0.5 to 30 units in ½-unit steps.