How do I convert peptide mg to mL?

Concentration in mcg per mL equals the vial size in mg multiplied by 1000, divided by the mL of bacteriostatic water you added. A 5mg vial in 2mL is 2,500mcg per mL. Because a U-100 syringe marks 1 mL as 100 units, divide that concentration by 100 to get mcg per unit, then divide your dose by that figure to get the mark to draw to.

How many units is 250mcg of BPC-157?

It depends entirely on how the vial was reconstituted. A 5mg vial in 2mL gives 25mcg per unit, so 250mcg is 10 units. The same 5mg vial in 1mL gives 50mcg per unit, so the identical 250mcg dose is 5 units. The dose reaching your body is the same; only the mark on the barrel changes. Never reuse a unit count from someone else without matching both the vial size and the water volume.

How much bacteriostatic water should I use?

There is no single correct volume, only trade-offs. More water lowers the concentration, which means more units for the same dose and easier accurate measurement of small doses, at the cost of a larger injection volume. Less water means fewer units and a smaller volume, but each unit carries more compound so a misread costs more. A common practical rule is to pick the volume that puts your typical dose between 10 and 30 units.

What is the most common peptide dosing mistake?

Confusing micrograms and milligrams. 250mcg is 0.25mg, so reading a milligram figure as a microgram dose is a 1,000-fold error. The next most common are reading units as micrograms, which they are not since a unit is a volume of 0.01 mL, and reusing an old unit count after changing the vial size, the water volume, or the product.

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HOW-TO7 min read·2026-09-18

Peptide mg to mL: The Conversion Chart for Every Common Vial Size

How to turn a vial in milligrams and a dose in micrograms into a mark on your syringe. The arithmetic, a reference chart, and the three mistakes that change your dose.

# Peptide mg to mL: The Conversion Chart for Every Common Vial Size Your vial is labeled in milligrams. Your dose is written in micrograms. Your syringe is marked in units. Nothing converts to anything else without arithmetic, and getting it wrong is the most common dosing error people make. This page walks the math once, then gives you a chart to check your own number against.

The Two Numbers That Set Everything

Only two inputs matter: how many milligrams are in the vial and how many milliliters of bacteriostatic water you add. Together they set the concentration, and concentration is what converts micrograms into a syringe mark.

Concentration in mcg/mL = (vial mg x 1000) / mL of BAC water

Then, because a U-100 insulin syringe marks 1 mL as 100 units, each single unit holds 0.01 mL:

mcg per unit = concentration / 100

Units to draw = your dose in mcg / mcg per unit

Work One By Hand

Take a 5mg vial reconstituted with 2mL of bacteriostatic water.

1. 5mg is 5,000mcg.

2. 5,000mcg / 2mL = 2,500mcg per mL.

3. 2,500 / 100 = 25mcg per unit.

4. A 250mcg dose is 250 / 25 = 10 units, drawn to the 10 mark.

Now change one input and watch the mark move. Same 5mg vial, reconstituted with 1mL instead of 2mL:

1. 5,000mcg / 1mL = 5,000mcg per mL.

2. 5,000 / 100 = 50mcg per unit.

3. That same 250mcg dose is now 250 / 50 = 5 units.

The dose reaching your body did not change. Only the geometry on the barrel changed. This is why you cannot borrow someone else's unit number from a forum post, and why the water volume field is not cosmetic.

The Chart

Micrograms per unit on a U-100 syringe, by vial size and water volume:

|---|---|---|---|---|

To get your units: divide your dose in mcg by the number in the cell.

### Common combinations, worked

10mg vial + 3mL water, 500mcg dose. 33.3mcg per unit. 500 / 33.3 = 15 units.

10mg vial + 2mL water, 250mcg dose. 50mcg per unit. 250 / 50 = 5 units.

5mg vial + 2mL water, 500mcg dose. 25mcg per unit. 500 / 25 = 20 units.

2mg vial + 1mL water, 100mcg dose. 20mcg per unit. 100 / 20 = 5 units.

Picking Your Water Volume

There is no correct answer, only trade-offs.

More water means a lower concentration and more units for the same dose. Small doses get easier to measure accurately, because a one-unit misread is a smaller share of the total. The cost is a larger injection volume.

Less water means a higher concentration and fewer units. Smaller injection volume, but each unit carries more compound, so the same one-unit misread costs you more.

A practical rule people use: pick the volume that puts your typical dose between 10 and 30 units. Below 10, measurement error starts to matter. Above 50, you are injecting more liquid than you need to.

The Three Mistakes That Change Your Dose

Confusing micrograms and milligrams. 250mcg is 0.25mg. Reading a milligram figure as a microgram dose is a 1,000-fold error. This is the one that does real harm.

Reading units as micrograms. The 10 mark is 10 units of volume, which is 0.10 mL. It is not 10mcg. What 10 units contains depends entirely on your concentration.

Reusing a number after changing anything. New vial size, different water volume, different product, even a different syringe type all invalidate the old mark. Recalculate whenever an input changes.

One more that costs you quietly: syringe dead space and trapped air. Both displace volume and shave the delivered dose, and neither shows up in the arithmetic.

Why Precision Matters More at Low Doses

Peptides dosed in the low hundreds of micrograms are where small barrel errors become large percentage errors. At 2,500mcg per mL, a three-unit misread is 75mcg. On a 250mcg target that is a 30 percent error. The same three-unit slip on a much lower concentration might be a rounding difference.

The lower your concentration relative to your dose, the more forgiving the math. That is the real argument for using more water on small doses.

What to Log

If you track nothing else, log the vial size, the water volume, and the resulting mcg per unit for each vial you open. That one line means you never recalculate under pressure, and it means that when a vial runs out sooner or later than expected you can see why.

Our [reconstitution calculators](/calculators) run this math for 26 compounds if you would rather not do it by hand. They are free and need no account.

•[How to reconstitute peptides](/blog/how-to-reconstitute-peptides)

•[BPC-157 dosage, mg, mL and cycle length](/blog/bpc-157-dosage-protocol)

•[Semaglutide dose to syringe units](/blog/semaglutide-dose-to-syringe-units)

•[How to store peptides correctly](/blog/how-to-store-peptides-correctly)

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*MyProtocolStack is a tracking and education tool. The arithmetic above is arithmetic. Which compound, which dose, and whether to use any of them at all are decisions for you and a licensed healthcare provider. Nothing here is medical advice.*

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