Dose-math tool

Units to mg converter, for peptides

By the Decadewise team Education only Last reviewed 20 July 2026 Runs in your browser

Units to mg converter

Converts the numbers you type. It does not recommend a dose.

Vial amount mg

Preset chips fill the vial field only. Any result already on screen recalculates to match.

Water added mL

Syringe type

Neither is selected until you choose one. The per-unit and syringe rows wait for it; the concentration does not.

Amount to convert, in milligrams mg

The concentration renders as soon as the vial and the water are filled in. The rows below it need a syringe type, then an amount to convert.

Concentration

One unit equals

That is a volume of

Reads as

Arithmetic only. Check the result against your own vial, your own reconstitution, and your own syringe before you trust any unit count.

Every calculation runs in this browser tab. Nothing typed here is stored, logged, or sent anywhere.

On this page

The converter Short answer How the math works One worked example How many units is 1mg? U-100 vs U-40? Why answers differ How many mL is 50 units? More dose math The disclaimer

Short answer

What a unit is: a unit on an insulin syringe is a volume mark, a fixed fraction of a milliliter. On a U-100 barrel that fraction is 0.01mL; on a U-40 it is 0.025mL.

What a milligram is: mass, the amount of peptide the vial label claims is inside. One milligram is 1,000mcg, which is why the converter prints both.

What joins them: concentration, the vial's milligrams divided by the water's milliliters. Until that number exists, no unit mark means any milligram amount at all.

What this page does: runs that arithmetic in both directions, milligrams to units and units back to milligrams, on whatever vial, water, and syringe get typed in above. It converts; it never suggests.

What happens to your numbers: nothing. Everything typed here is converted inside this browser tab and never sent or stored anywhere.

How the math works

Units are volume: the number printed on an insulin syringe counts fractions of a milliliter, and nothing else. U-100 means 100 units per mL, U-40 means 40 units per mL, and the barrel has no idea what is dissolved in the liquid.

Milligrams are mass: the vial label states how much peptide arrived in the vial, and that figure never appears on any syringe. The two systems only meet through the water.

Concentration is the bridge: vial milligrams divided by water milliliters gives mg per mL, and mg per mL divided by the syringe's units per mL gives the milligrams inside a single unit. A 20mg vial with 2mL of water comes out to 10mg per mL, so one U-100 unit holds 0.1mg, or 100mcg.

One equation, both directions: milligrams divided by the per-unit value lands on the unit mark, and a unit mark multiplied by the per-unit value lands back on the milligrams. Everything on this page is that division, so there is nothing here to cite and nothing to trust but the arithmetic.

One worked example

The labeled example: a 20mg vial, 2mL of bacteriostatic water, and a U-100 syringe. Every figure below is arithmetic on those three choices, not a chart for any particular vial in anyone's hands.

Worked example: 20mg vial + 2mL water = 10mg per mL, U-100 syringe, 1 unit = 0.1mg (100mcg)

Milligrams	Volume on the barrel	Reads as, U-100
0.5mg	0.05mL	5 units
1mg	0.1mL	10 units
2mg	0.2mL	20 units
2.5mg	0.25mL	25 units
5mg	0.5mL	50 units

Change the vial, the water, or the syringe scale and every figure in this table changes with it.

How many units is 1mg?

There is no fixed number, because units measure volume and milligrams measure mass, and only the concentration connects them. At 10mg per mL (a 20mg vial plus 2mL of water), 1mg reads as 10 units on a U-100 syringe; at 5mg per mL the same 1mg reads as 20 units.

What is the difference between U-100 and U-40?

The barrel scale. U-100 packs 100 units into each mL, so one unit is 0.01mL; U-40 packs 40 units into each mL, so one unit is 0.025mL, two and a half times the liquid per mark. The scale sets volume only, and the milligrams at any mark still come from the vial and the water.

Why does my answer differ from the chart?

Because every chart carries its own vial size, water amount, and syringe scale, and those three assumptions are usually printed small or left out entirely. A 2.5mg amount is 25 units at 10mg per mL and 50 units at 5mg per mL. Match all three assumptions and the numbers agree; miss any one and they never will.

How many mL is 50 units?

On a U-100 syringe, 50 units is 0.5mL. On a U-40, the same 50-unit mark is 1.25mL. A unit count is a volume reading and never a mass, so the milligrams sitting inside that volume only exist once the concentration is known.

More dose math

The rest of the cluster: this converter is one tool in the dose-math library we maintain. The neighboring pages:

Peptide dose math, the hub: every dose-math page and tool, collected in one place.
Reconstitution calculator: vial plus water to concentration, then the draw volume for any milligram figure you bring to it.
Bacteriostatic water calculator: works the bridge equation backwards, from a vial and a chosen concentration to the water volume.
Concentration vs dose: the explainer behind nearly every wrong unit count we have ever untangled.
Tirzepatide dosage guide: this same units math inside a full compound reference, with the trial record attached.
The embeddable version: this converter as a widget any other site can host with one line, free, with an attribution link back.

The disclaimer

Every page is reviewed by medical professionals before it ships, and written with longtime biohackers who were doing this before it was a trend. Reviewed still does not mean prescribed: nothing here is medical advice.

It is research, trial data, and reported use, with the numbers intact so you can check them. For decisions about your body, see a doctor who can look at your labs.