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Peptide reconstitution calculator by SoftMaxx AI

Units on a U-100 syringe = dose ÷ (vial amount ÷ water) × 100. Type your vial, your water and the dose you were given; get mL and units, checked against mg/mcg mix-ups, syringe size and the 28-day discard rule.

Math only · Nothing you type leaves your browser · For adults 18+ · Updated 2026-09-30

The formula. Concentration = vial amount ÷ water added. Volume to draw (mL) = dose ÷ concentration. Units on a U-100 syringe = mL × 100, because 1 unit = 0.01 mL on every U-100 syringe, whatever its size.

units = dose (mg) ÷ (vial mg ÷ water mL) × 100

Example of the arithmetic only: a 5 mg vial with 2 mL of water holds 2.5 mg per mL, so 0.25 mg is 0.1 mL, which is 10 units. Change any number and the answer changes.

Units to draw from a vial you mixed

Type what is printed on your vial, the water you added, and the dose you were given.

Your vial is labelled in
The number on the vial label.
Bacteriostatic or sterile water you put in.
The amount you were told to take.
Dose is in
Your syringe
Smallest marking on it
Leave empty for 3 mL. Most vials hold 2 to 3 mL.

This calculator does math on the numbers you type. It does not know what you have or whether any amount is right for you, and it never suggests a dose. Check the result with your pharmacist or prescriber.

How much water for a round number of units

Pick the units you want to see on the syringe; this solves for the water.

Dose is in
For example 10, 20 or 50.
Leave empty for 3 mL.

This calculator does math on the numbers you type. It does not know what you have or whether any amount is right for you, and it never suggests a dose. Check the result with your pharmacist or prescriber.

Vial planner: doses, run-out and discard dates, cost

FDA advises discarding a multi-dose vial 28 days after first use, even if some is left.

Dose is in
However many times a week you were told.
Any currency; used only for the cost lines.
How many vials a period of weeks needs.

This calculator does math on the numbers you type. It does not know what you have or whether any amount is right for you, and it never suggests a dose. Check the result with your pharmacist or prescriber.

Half-life chart: relative level over time

Uses the half-life printed in each FDA label. It draws a relative level, not a blood concentration, and says nothing about effect.

Label half-life (Wegovy / Zepbound)
The chart then shows the weeks after the last one.

Injection-site rotation log

The Wegovy and Zepbound labels both say: “Rotate injection sites with each dose.” Tap the site you used. The log stays in this browser only.

Manufacturer pre-blended vial (two or three components)

Check: Use this only for a vial the manufacturer pre-blended. Do not mix two products in one vial yourself: the bacteriostatic water label warns some drugs are incompatible in the same vehicle, and there is no stability data for home co-mixes.

This calculator does math on the numbers you type. It does not know what you have or whether any amount is right for you, and it never suggests a dose. Check the result with your pharmacist or prescriber.

Questions about the math

Does a smaller syringe change the units?

No. On every U-100 syringe 1 unit is 0.01 mL. A 0.3 mL syringe only holds less and has finer markings. A U-40 syringe is different: 1 unit is 0.025 mL, so the same mL reads as fewer units.

Why does this tool refuse IU for most peptides?

An IU is a bioassay activity unit defined for one substance against its own reference standard. Somatropin has one (3 IU per mg, WHO standard 98/574). Most peptides have none, so mg and IU do not convert. If your vial is labelled in IU, do all the math in IU.

Why does it stop when the dose is bigger than the vial?

Because a dose larger than everything in the vial is almost always an mg and mcg mix-up, which changes a dose 1,000-fold. The tool shows no number until the inputs make sense.

Where does the 28-day discard date come from?

It is the USP <797> multiple-dose default, and FDA advises consumers to discard multi-dose vials 28 days after first use even if medicine remains.

About this tool

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